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ch. 5& 8

Terms in this set (12)

SEXUAL ANATOMY
Despite their different appearances, male and female sex organs arise from the same structures and fulfill many of the same functions. Gonads (ovaries in females and testes in males) produce germ cells and sex hormones. Germ cells are called ova (eggs) in females and sperm in males. Ova and sperm are the basic units of reproduction.

According to the American Psychological Association, experts estimate that as many as 1 in 1500 infants, due to genetic or hormonal abnormalities, is born with genitals thatPage 113 cannot easily be assigned to the category of male or female, a condition known as intersex. Parents and doctors of intersex infants sometimes use surgery to assign these children to a particular sex, but many adults who have undergone such procedures are now calling for an end to these surgeries so that people with intersex conditions can choose for themselves when the time is right for them. Intersex is not the same as transgender, which is the word used to describe a person whose genitals align with the category male or female, but who does not identify with the gender (masculine or feminine) typically assigned to those genitals. Transgender will be discussed more fully later in this chapter.

Female Sex Organs

The external sex organs, or genitals, of the female are called the vulva (Figure 5.1). The vulva, commonly confused with the vagina, includes the mons pubis, labia majora and minora, clitoris, and urethral and vaginal openings. The mons pubis, a rounded mass of fatty tissue over the pubic bone, becomes covered with hair during puberty (biological maturation). Below it are two paired folds of skin called the labia majora (outer lips) and the labia minora (inner lips). Enclosed within these folds are the clitoris, the opening of the urethra, and the opening of the vagina. Despite a rise in surgeries designed to reduce them, the labia majora vary widely in size, color, shape, and overall appearance, and they often play a significant role in sexual sensation and pleasure.


FIGURE 5.1 The female sex organs. (a) An external view of the vulva. (b) An internal view of the female pelvis.
The clitoris is highly sensitive to stimulation and also plays an important role in female sexual arousal, orgasm, and pleasure. The clitoris consists of 8000 nerve endings concentrated in the glans, or head. The clitoris may be externally visible between the labia. It then extends internally into the anterior wall of the vagina (Figure 5.1b). Inside the clitoris, spongy, erectile tissue fills with blood during sexual excitement, creating engorgement of the genitals. The clitoral hood, or prepuce, covers the glans and is formed from the upper portion of the inner lips.

The female urethra is a duct that leads directly from the urinary bladder to its opening between the clitoris and the opening of the vagina. The urethra conducts urine from the bladder. Women have a much shorter urethra than men and as a result are more likely to suffer from urinary tract infections, or UTIs. Both males and females should urinate after sexual activity to cleanse this tube.

Some women are able to expel fluid or ejaculate during sexual activity. If so, the fluid exits the urethra, not the vagina. This fluid has been tested and is typically not urine, although some remnants of urine have been found simply because urine travels out of the same tube. This fluid is similar to prostatic fluid in men.

The vagina is the passage that leads to the internal sexual organs and can be used for sexual intercourse and penetration. It is a potential birth canal and allows menstrual fluid to be expelled from the uterus. Located about 1-2 inches internally in the vagina, is the Gräfenberg- or G-spot. This spot—or more accurately, region—is the root of the clitoris and can be highly sensitive in some women. Projecting into the upper part of the vagina is the cervix, which is the opening of the Page 114uterus—or womb—where a fertilized egg is implanted and develops into a fetus.

A pair of fallopian tubes (or oviducts) extends from the top of the uterus. The end of each oviduct surrounds an ovary and guides the mature ovum down into the uterus after the egg exits the ovary.

QUICK STATS

20 million or more sperm per milliliter of semen is considered a normal sperm count.

—National Library of Medicine, 2014
Male Sex Organs

Male external sex organs, or genitals, are the penis and the scrotum (Figure 5.2). The penis consists of the glans, often referred to as the head, which is typically the most sensitive part of the penis. The shaft extends from the head to the body of the penis and is made up of spongy tissue that becomes engorged with blood during sexual excitement, causing the organ to enlarge and become erect.


FIGURE 5.2 The male sex organs. (a) An external view. (b) An internal view.
The scrotum is a pouch that contains a pair of sperm-producing male gonads, called testes. The scrotum maintains the testes at a temperature approximately 5°F below that of the rest of the body—that is, at about 93.6°F. The process of sperm production is extremely heat sensitive. In hot temperatures, the muscles in the scrotum relax and the testes move away from the heat of the body. This ability to regulate the temperature of the testes is important because elevated testicular temperature can interfere with normal sperm production. Men should regularly perform testicular exams and examine the testes for any unusual growths. The best place to do this is in the shower because it is warm and the scrotal sac will hang farther away from the body.

The male urethra is a tube that runs through the entire length of the penis. The urethra carries both urine and semen (sperm-carrying fluid) to the opening at the tip of the penis. The Cowper's glands are two small structures flanking the urethra. During sexual arousal, these glands excrete a clear, mucus-like fluid that appears at the tip of the penis. This preejaculatory fluid is thought to help lubricate the urethra to facilitate the passage of sperm and flush out any remaining urine in the tube. The release of preejaculatory fluid is an involuntary reflex and may contain sperm, so withdrawal of the penis before ejaculation is not a reliable form of contraception. It is also possible to contract a sexually transmitted infection (STI) from preejaculatory fluid.

Starting at about age 14, males begin producing sperm, around 400 million per day. The sperm take the following journey:

Sperm are produced inside a maze of tiny, tightly packed tubules within the testes. As they begin to mature, sperm flow into a single storage tube called the epididymis, which lies on the surface of each testis.
Sperm move from each epididymis into another tube—called the vas deferens.Page 115
The two vasa deferentia eventually merge into a pair of seminal vesicles, whose secretions provide nutrients for the sperm. The sperm then pass through an organ called the prostate gland, where they pick up a milky fluid and become semen.
On the final stage of their journey, sperm flow into the ejaculatory ducts. Although urine and semen share a common passage, they are prevented from mixing together by muscles that control their entry into the urethra.
The smooth, rounded tip of the penis is the highly sensitive glans, an important component in sexual arousal (Figure 5.2a shows a frontal view; Figure 5.2b shows a side view). The glans is partially covered by the foreskin, or prepuce, a retractable fold of skin that is removed by circumcision in about 55% of newborn males in the United States. Circumcision is performed for cultural, religious, and medical reasons. Rates of circumcision vary widely among groups (see the box "Genital Alteration").

DIVERSITY MATTERS: Genital Alteration

The alteration of the appearance and function of children's genitalia, either shortly after birth or as part of a puberty rite, provokes much controversy worldwide. The most common form of genital alteration is male circumcision—the removal of the foreskin of the penis. Circumcision is a relatively minor surgical procedure that is performed for a variety of cultural, religious, aesthetic, and medical reasons. Worldwide an estimated one-third of males are circumcised. In the United States a little more than one-half of male newborns are circumcised (from a high of nearly 90% in the 1960s); over time, fewer American parents are having their sons circumcised.

The procedure, though minor, carries some medical risks, including bleeding, infection, damage to the penis, and even death. Circumcision causes pain to the infant, although most pain can be alleviated with appropriate use of local anesthetic. Circumcision may change the sensitivity of the penis, and some critics claim that it can diminish a man's sexual pleasure. Opponents of circumcision point to the fact that most of the world's men are uncircumcised; why perform surgery, they ask, when there is no clear need for it?

On the other side of the debate, a number of health benefits are claimed to be associated with circumcision. Proponents of the procedure argue that it promotes cleanliness and reduces the risk of urinary tract infections in newborns and sexually transmitted infections in later life. The American Academy of Pediatrics states that the "preventive health benefits of elective circumcision of male newborns outweigh the risks of the procedure," so that families who choose the procedure should have access to it. Studies conducted in developing countries have shown that circumcision can reduce a man's risk of acquiring human immunodeficiency virus (HIV), herpes simplex virus type 2, human papillomavirus (HPV), and genital ulcer disease through heterosexual contact. Male circumcision has also been shown to lower rates of HPV, genital ulcer disease, bacterial vaginosis, and trichomoniasis among female partners, although one study in Uganda showed increased rates of HIV infection for women whose male partners were circumcised. Ultimately education about STIs, the practice of abstinence or low-risk sexual behaviors, and the use of barrier methods such as condoms have a far greater impact on the transmission of STIs than does circumcision.

Far more controversial is the practice of female genital cutting (FGC), also called female genital mutilation or modification. FGC ranges from removal of the external genitalia (including the clitoris and labia) to sewing up the labia but leaving a small opening through which urine and menstrual fluid can pass. A common explanation for the practice is that FGC controls a woman's sexuality and ensures she remains a virgin before marriage. Other explanations refer to empowerment for girls: Through the bonding and educational experiences surrounding the ceremonies, girls attain a status similar to cohorts of boys the same age who are undergoing circumcision. These explanations are cultural rather than medical.

Each year about 3 million female children undergo FGC, usually between infancy and age 15, and about 140 million women worldwide are estimated to have had some form of genital cutting. FGC is often performed under unsterile conditions and without adequate anesthesia. Serious complications are common and include severe pain, infection, bleeding, and death. Common long-term health issues include infertility, difficulties with childbirth, and problems with urinary and sexual function.

The World Health Organization has come out strongly against FGC, declaring it a violation of the human rights of girls and women. FGC is now illegal in many countries, including the United States, but it is still performed on large numbers of girls where the cultural tradition persists. In a parallel move, the American Congress of Obstetricians and Gynecologists has spoken out against the practice of cosmetic genital surgeries in the United States and elsewhere, calling the procedures "not medically necessary." Though these cosmetic surgeries are performed under sterile and voluntary conditions, it is worth noting that all forms of cutting mentioned here are related to cultural beliefs regarding the purpose and appearance of female genitals.

sources: Boyle, E. H., and A. C. Corl. 2010. Law and culture in a global context: Interventions to eradicate female genital cutting. Annual Review of Law and Social Science 6: 195-215; Centers for Disease Control and Prevention. 2011. Trends in in-hospital newborn male circumcision—United States, 1999-2010. MMWR 60(34): 1167-1168; World Health Organization. 2012. Female Genital Mutilation (http://www.who.int/topics/female_genital_mutilation/en/); Tobian, A. A. R., et al. 2014. Male circumcision: A globally relevant but under-utilized method for the prevention of HIV and other sexually transmitted infections. Annual Review of Medicine 65: 293-306.
Ask Yourself

QUESTIONS FOR CRITICAL THINKING AND REFLECTION
What are your personal views on circumcision? What are your views about other forms of genital cutting? Who or what has influenced those opinions? Are the bases of your views primarily cultural, moral, or medical? If you had a son or daughter, would you have their genitals altered?
HORMONES AND THE REPRODUCTIVE LIFE CYCLE
The sex hormones produced by the ovaries or testes have a major influence on the development and function of the sexual organs throughout life. In addition to their effects on these organs, sex hormones influence many other parts of the body, including the brain.

Both males and females produce testosterone, estrogens, and progestogens; however, the quantities differ in male and female bodies. The male sex hormones, made by the testes, are called androgens, the most important of which is testosterone. Males will produce lower levels of estrogen and progesterone. The female sex hormones, produced by the ovaries, belong to two groups: estrogens and progestogens. The ovaries also produce a small amount of testosterone. The adrenal glands also produce sex hormones in both males and females.

Sex hormones are regulated by the hormones of the pituitary gland, located at the base of the brain. This gland in turn is controlled by hormones produced by the hypothalamus in the brain.

In Chapter 19, we examine endocrine-disrupting chemicals (EDCs), an example of a substance from the environment that acts like hormones and disrupts normal endocrine activity, particularly activity related to reproduction and development. The most studied EDCs are environmental estrogens, which mimic the female sex hormone estrogen and can duplicate or exaggerate its effects. Other EDCs can block estrogen, mimic or block androgens (male sex hormones), or otherwise alter hormonal responses in the body.

Differentiation of the Embryo

How do we become what might eventually be called a girl or a boy? All human cells typically contain 23 pairs of chromosomes (Figure 5.3). In 22 of the pairs, the two partner chromosomes match. But in the 23rd pair, one comes from the mother and one from the father; these are called the sex chromosomes. Mothers contribute an X and fathers an X or a Y, making the Y chromosome the primary determinant of a child's sex. Females are XX and males are XY, and this genetic fact occurs at the moment of conception.


FIGURE 5.3 A normal set of chromosomes. The first 22 pairs are matched, but the last pair (the sex chromosomes) does not match, indicating the person carrying these chromosomes is male.
© Biophoto Associates/Photo Researchers/Science Source
Abnormalities sometimes occur in the sex chromosomes; the two most common disorders of sex chromosomes—also known as intersex conditions—are Klinefelter syndrome and Turner syndrome. Klinefelter syndrome, a condition in which a male carries two or more X chromosomes in addition to the Y chromosome, occurs in about 1 in 1000 males and causes infertility and underdeveloped genitalia. Turner syndrome occurs in about 1 in 2500 females. Women with Turner have only a single complete X chromosome. People with this condition will need technological assistance to have children and can sometimes have other medical problems.Page 116

Genetic sex dictates whether the undifferentiated gonads become ovaries or testes. If a Y chromosome is present, the gonads become testes and produce the male hormone testosterone. Testosterone circulates throughout the body and causes the undifferentiated reproductive structures to develop into male sex organs (e.g., penis and scrotum). If the chromosomal arrangement is XX, the gonads become ovaries and the genital structures develop into a vagina, clitoris, and labia. Some researchers believe that this process, often referred to as sexual differentiation, is influenced solely by the presence or absence of testosterone. Others, however, believe that the relationships among chromosomes, genes, and hormones are far more complex, and that intersex conditions are a natural variation of these complicated and not always binary processes.

Exposure to hormones affects more than the sexual organs: It also influences development of the brain. Some research in this area has suggested that males tend to perform better than females at tasks requiring spatial skills, and that females perform better than males on tests of verbal skills. Proponents of this research posit that androgens are involved in this gender difference because genetic females who are exposed to androgens sometimes perform better at spatial skills and genetic males deprived of these hormones do worse. There are many criticisms of this research, however, because it is very difficult to separate the ways that boys and girls are treated—even infants—from the effects of biological hormones on their abilities.

What is important to keep in mind is that each person is a combination of biological, environmental, and culturalPage 117 events. Biology acts on the cells in the body, including the brain. The physical and social environment then shapes this biological foundation to produce unique individuals. Some researchers point to the human past as a way to explain sex differences in language and visual-spatial skills. For example, the early division of labor with men as hunters and women as food gatherers, camp organizers, and child raisers may have promoted the development of different skills based on gender, including visual-spatial skills in men and communication skills in women. Some researchers argue that men and women are still socialized into distinct gender roles, and that this plays a significant role in how their brains develop over time.


Once they reach puberty, adolescents are biologically adults, but it will take several more years for them to become adults in social and psychological terms.
© Cathy Yeulet/123RF
Female Sexual Maturation

Although humans are typically sexually differentiated at birth, the differences between males and females are accentuated at puberty, the period during which the reproductive system matures, secondary sex characteristics develop, and the bodies of males and females begin to appear more distinctive (while still overlapping in many ways). The changes of puberty are induced by testosterone in the male and estrogen and progesterone in the female.

Puberty in Females

The first sign of puberty in girls is often breast development, followed by a rounding of the hips and buttocks. As the breasts develop, hair appears in the pubic region and later in the underarms. Shortly after the onset of breast development, girls show an increase in growth rate. Breast development usually begins between ages 8 and 13, and the time of rapid body growth occurs between ages 9 and 15.Page 118

The Menstrual Cycle

A major landmark of puberty for most young women is the onset of the menstrual cycle, the monthly ovarian cycle that leads to menstruation (loss of blood and tissue lining the uterus) in the absence of pregnancy. The timing of menarche (the first menstrual period) varies with several factors, including race/ethnicity, genetics, and nutritional status. The "normal" range for the onset of menstruation is wide; some girls experience menarche as young as 9 or 10, and others when they are 16 or 17 years old. The current average age of menarche in the United States is around 12½ years of age. Two hundred years ago, the average age of menarche was closer to 17 years. The earlier onset of menarche today is probably due in large part to nutritional factors. When age at menarche is examined worldwide, studies show that menarche tends to come later to girls who live in relative poverty with diets lacking in protein and calories. Obesity is strongly correlated with earlier menarche, which may explain the current trend for earlier menarche in the United States and many other countries. Some experts worry that exposure to estrogen-like chemicals in the environment, including estrogenized food, may also contribute to earlier menarche. Because it is the biological norm for women born with female sex organs to menstruate, girls should check with a health care provider if their menstrual cycle does not begin during their adolescence. Although it might be normal, it might also indicate a disease or other problem.

The day of the onset of bleeding is considered to be day 1 of the menstrual cycle. For the purposes of our discussion, a cycle of 28 days will be used; however, normal cycles vary in length from 21 to 35 days. The menstrual cycle consists of the following four phases (Figure 5.4):


FIGURE 5.4 The menstrual cycle.
Menses. During menses, characterized by the menstrual flow, blood levels of hormones from the ovaries and the pituitary gland are relatively low. This phase of the cycle usually lasts from day 1 to about day 5.
Estrogenic phase. The estrogenic phase begins when the menstrual flow ceases and the pituitary gland begins to produce increasing amounts of follicle-stimulating hormone (FSH) and luteinizing hormone (LH). Under the influence of FSH, an egg-containing ovarian follicle begins to mature, producing increasingly higher amounts of estrogen. Stimulated by estrogen, the endometrium (the uterine lining) thickens with large numbers of blood vessels and uterine glands.
Ovulation. A surge of a potent estrogen called estradiol from the follicle causes the pituitary gland to release a large burst of LH and a smaller amount of FSH. The high concentration of LH stimulates the developing follicle to release its ovum. This event is known as ovulation. After ovulation, the follicle is transformed into the corpus luteum, which produces progesterone and estrogen. Ovulation theoretically occurs about 14 days prior to the onset of menstrual flow, with the window of greatest fertility occurring from a few days before ovulation to about one day after. This information has been used to attempt to predict the most fertile time during the menstrual cycle for fertility treatments and natural family planning methods (see Chapter 6). However, a recent study showed that even women with regular menstrual cycles often have unpredictable ovulation, and can actually be fertile on any day of the month, including during menstruation. The "window of fertility" is especially unpredictable in teenagers and women who are approaching menopause.
Progestational phase. During the progestational phase of the cycle, the amount of progesterone secreted from the corpus luteum increases and remains high until the onset of the next menses. Under the influence of estrogen and progesterone, the endometrium continues to develop, readying itself to receive and nourish a fertilized ovum. If pregnancy occurs, the fertilized egg produces the hormone human chorionic gonadotropin (hCG), Page 119which maintains the corpus luteum. Thus levels of ovarian hormones remain high and the uterine lining is preserved, preventing menses. hCG is the hormone detected by pregnancy tests.
If pregnancy does not occur, the corpus luteum degenerates, and estrogen and progesterone levels gradually fall. Below certain hormonal levels, the endometrium can no longer be maintained, and it begins to slough off, initiating menses. As the levels of ovarian hormones fall, a slight rise in LH and FSH occurs, and a new menstrual cycle begins.

QUICK STATS

75% of women experience premenstrual symptoms during their child-bearing years.

—National Institutes of Health, 2012
Menstrual Problems

Menstruation is a normal biological process, and physical or emotional symptoms associated with the menstrual cycle are common. Many women experience menstrual cramps, the severity of which tends to vary from cycle to cycle. Dysmenorrhea, discomfort associated with menstruation, can include any combination of the following symptoms: lower abdominal cramps, backache, vomiting, nausea, bloating, diarrhea, headache, and fatigue. Many of these symptoms can be attributed to uterine muscular contractions caused by chemicals called prostaglandins. Nonsteroidal anti-inflammatory drugs (NSAIDs) such as ibuprofen often relieve dysmenorrhea by blocking the effects of prostaglandins. Oral contraceptives are also effective in reducing dysmenorrheal symptoms in most women.

Many women experience transient emotional symptoms prior to the onset of their menstrual flow. Depending on their severity, these symptoms may be categorized along a continuum: premenstrual tension, premenstrual syndrome (PMS), and premenstrual dysphoric disorder (PMDD). Premenstrual tension symptoms are mild and may include negative mood changes and physical symptoms such as abdominal cramping and backache. More severe symptoms are classified as PMS; very severe symptoms that impair normal daily and social functioning are classified as PMDD. All three conditions share a definite pattern. Symptoms appear prior to the onset of menses and disappear within a few days after the start of menstruation. Premenstrual tension is quite common, PMS affects about 1 in 5 women, and PMDD affects fewer than 1 in 10 women.

Symptoms associated with PMS and PMDD can include breast tenderness, water retention (bloating), headache, fatigue, insomnia or excessive sleep, appetite changes, food cravings, irritability, anger, increased interpersonal conflict, depression, anxiety, tearfulness, inability to concentrate, social withdrawal, and the sense of being out of control or overwhelmed.

Despite many research studies, the causes of PMS and PMDD are still unknown, and it is unclear why some women are more vulnerable than others. These conditions are especially tricky to research because the symptoms overlap with many other conditions, and they are also normal responses to stress, which is common. Research has focused on a variety of substances in the body that may fluctuate with the menstrual cycle. Most researchers agree that PMS is probably caused by a combination of hormonal, neurological, genetic, dietary, and psychological factors.

The following strategies provide relief for many women with premenstrual symptoms, and all of them can contribute to a healthy lifestyle at any time:

Limit salt intake. Salt promotes water retention and bloating.
Exercise. Women who exercise may experience fewer symptoms before and after menstrual periods.
Don't use alcohol or tobacco. Alcohol and tobacco may aggravate certain symptoms of PMS and PMDD.
Eat a nutritious diet. Choose a low-fat diet rich in complex carbohydrates from vegetables; fruits; and whole-grain breads, cereals, and pasta. Get enough calcium from calcium-rich foods and, if needed, supplements. Minimize your intake of sugar and caffeine, and avoid chocolate, which is rich in both.
Relax. Stress reduction is always beneficial, and stressful events can trigger PMS symptoms. Try relaxation techniques during the premenstrual time. Orgasms, including those from masturbation, can also help reduce stress and relieve cramping.
If you suffer persistent premenstrual symptoms, keep a daily diary to track the types of symptoms, their severity, and their correlation with your menstrual cycle. Some women find help after being evaluated by a health care provider.

Selective serotonin reuptake inhibitors (SSRIs), such as Prozac and Zoloft, are sometimes used to treat PMS and PMDD. Until recently, women using SSRIs took the medication throughout the entire menstrual cycle, but taking the medication during just the progestational phase of the cycle is effective in some women. However, these medications are not without side effects and may negatively affect sexual functioning—specifically causing low desire as well as difficulty with arousal and attaining orgasm.Page 120

Other drug treatments for PMS and PMDD include certain oral contraceptives, diuretics to minimize water retention, and NSAIDs such as ibuprofen. A number of vitamins, minerals, and other dietary supplements have also been studied for PMS relief. Only one supplement, calcium, has been shown to provide relief in rigorous clinical studies; several others show promise, but more research is needed.

Male Sexual Maturation

Reproductive maturation of boys occurs about two years later than that of girls; it usually begins at about age 10 or 11 (Figure 5.5). Testicular growth is usually the first obvious sign of sexual maturity in boys. The penis also grows at this time, reaching adult size by about age 18. Pubic hair starts to develop after the genitals begin increasing in size, with underarm and facial hair gradually appearing. Hair on the chest, back, and abdomen increases later in development. Facial hair often continues to get thicker and darker for several years after puberty. The voice deepens as a result of the lengthening and thickening of the vocal cords. A small amount of breast development occurs in many boys during puberty. This is called gynecomastia, and it usually decreases after puberty. Excessive breast growth can occur in some boys, especially if they are overweight.


FIGURE 5.5 Milestones in sexual maturation of girls and boys.
source: The Merck Manual Home Health Handbook, Online Version. © 2010-2013 Merck Sharpe & Dohme Corp., a subsidiary of Merck & Co., Inc., Whitehouse Station, NJ, USA (http://merckmanuals.com/home/childrens_health_issues/adolescents/physical_andsexual_development.html).
Boys grow taller for about six years after the first signs of puberty, with a rapid period of growth about two years after puberty starts. Largely because of the influence of testosterone, muscle development and bone density are much greater in males than in females. By adulthood, men, as a group, have one and a half times the lean body mass of women as a group, and nearly half the body fat. However, many individual men and women fall outside these averages.

Ask Yourself

QUESTIONS FOR CRITICAL THINKING AND REFLECTION
Think about your own experience as you matured during puberty and adolescence. In what ways did these changes affect your life? How did they contribute to the person you are today?
Aging and Human Sexuality

Hormone production and sexual functioning change as we age. Although sexual functioning may diminish as one ages, sexuality and sensuality can continue to be a source of great pleasure and satisfaction. A recent study of sexuality in older Americans found that three-fourths of 57- to 64-year-olds were sexually active (defined as having had at least one sexual partner in the past year). Half of those people aged 65-74, and about one-fourth of people aged 75-85, remained sexually active. People who remain healthy and active are much more likely to continue to be sexually active in their older years.

Menopause

As a woman approaches age 50, her ovaries gradually cease to function and she enters menopause, the Page 121cessation of menstruation (Table 5.1). For some women, the associated drop in hormone production causes troublesome symptoms. The most common physical symptom of menopause is the hot flash, a sensation of warmth rising to the face from the upper chest, with or without perspiration and chills. During a hot flash, skin temperature can rise by more than 10 degrees. Other menopausal symptoms can include vaginal dryness, low libido, painful intercourse, night sweats, insomnia, thinning of head hair, and mood changes. Osteoporosis—decreasing bone density—can develop, making older women more vulnerable to fractures.

Table 5.1 Reproductive Aging in Women
AGE*
SIGNS & SYMPTOMS—WHAT'S HAPPENING
STAGE OF REPRODUCTION
9-15
First period; variable menstrual cycles
Menarche; beginning reproductive years
16-30
Regular menstrual cycle; fertility peaking
Reproductive years
31-42
Regular menstrual cycle; fertility progressively declining
Reproductive years
Early 40s
Lengths of menstrual cycle vary increasingly
Menopausal transition
Late 40s-early 50s
Two or more skipped periods; hot flashes, irritability, and sleep disturbance; bone loss begins
Menopausal transition
45-55
Final period (i.e., no period for 12 months)
Menopause
50s and beyond
Vaginal dryness, bone loss. Hot flashes can persist (for a few women, into their 60s and 70s).
Postmenopause
*Women vary a great deal in the ages at which they go through these stages. The average length of menopause and the transition leading up to it is four years, but for some women symptoms may last only a few months, and for others, 10 years.

source: American Society for Reproductive Medicine. 2012. Reproductive Aging in Women (http://www.reproductivefacts.org).

Although sexual physiology changes as people get older, many men and women readily adjust to these alterations.
© Big Cheese Photo/360/Getty Images RF
As a result of decreased estrogen production during menopause, the vaginal walls become thin, and lubrication in response to sexual arousal can diminish. Sexual intercourse may become painful. Hormonal treatment or the use of lubricants during intercourse can minimize these problems.

Cross-cultural studies comparing Japanese with North American women dispel the idea that hot flashes and other menopausal reactions are universal. A diet of fish and vegetables; an exercise regimen of cycling, walking, or farming; and cultural ideas about the meaning of bodily changes positively affected the Japanese experience of menopause among the women studied.

In Western medicine, doctors once regularly prescribed estrogen for postmenopausal women to relieve hot flashes, vaginal dryness, bone loss, and a host of other symptoms in a regimen called hormone replacement therapy, or HRT. However, in the past several years, reanalysis of the data on potential side effects, which include cardiovascular disease, blood clots, and breast cancer, has resulted in more individualized approaches—including, for example, low-dose estrogen, sometimes in the form of a patch, cream, or vaginal ring, designed to treat specific symptoms of menopause and with a reduced risk of side effects. (See Chapters 12, 15, and 22 for more information about osteoporosis and heart disease.)

Aging Male Syndrome

Between the ages of 35 and 65, men experience a gradual decline in testosterone production, resulting in the aging male syndrome, sometimes referred to as male menopause or andropause. Some experts prefer the term aging male syndrome because the process is much more gradual than female menopause. Symptoms vary widely, but most men experience at least some of the followingPage 122 symptoms as they age: loss of muscle mass, increased fat mass, decreased sex drive, erectile problems, depressed mood, irritability, difficulties with concentration, increased urination, loss of bone mineral density, and sleep difficulties. In some cases, men who have low testosterone may benefit from carefully prescribed testosterone replacement therapy.

As men get older, they depend more on direct physical stimulation for sexual arousal. They take longer to achieve an erection and find it more difficult to maintain; orgasmic contractions are less intense. Older men with erectile dysfunction often use prescription medications that increase blood flow to the penis, resulting in a firmer erection.

Unlike women, who are born with all the eggs they will ever have and stop being fertile at menopause, men continue to produce sperm throughout their lives and can sometimes father children well into their eighties and even nineties. Starting at about age 30, however, men become gradually less fertile. The pregnancy rate drops to 50% for couples with a man over age 35, regardless of the woman's age. Men over age 40 are more likely to produce children with health problems such as autism, schizophrenia, and Down syndrome.
HORMONES AND THE REPRODUCTIVE LIFE CYCLE
The sex hormones produced by the ovaries or testes have a major influence on the development and function of the sexual organs throughout life. In addition to their effects on these organs, sex hormones influence many other parts of the body, including the brain.

Both males and females produce testosterone, estrogens, and progestogens; however, the quantities differ in male and female bodies. The male sex hormones, made by the testes, are called androgens, the most important of which is testosterone. Males will produce lower levels of estrogen and progesterone. The female sex hormones, produced by the ovaries, belong to two groups: estrogens and progestogens. The ovaries also produce a small amount of testosterone. The adrenal glands also produce sex hormones in both males and females.

Sex hormones are regulated by the hormones of the pituitary gland, located at the base of the brain. This gland in turn is controlled by hormones produced by the hypothalamus in the brain.

In Chapter 19, we examine endocrine-disrupting chemicals (EDCs), an example of a substance from the environment that acts like hormones and disrupts normal endocrine activity, particularly activity related to reproduction and development. The most studied EDCs are environmental estrogens, which mimic the female sex hormone estrogen and can duplicate or exaggerate its effects. Other EDCs can block estrogen, mimic or block androgens (male sex hormones), or otherwise alter hormonal responses in the body.

Differentiation of the Embryo

How do we become what might eventually be called a girl or a boy? All human cells typically contain 23 pairs of chromosomes (Figure 5.3). In 22 of the pairs, the two partner chromosomes match. But in the 23rd pair, one comes from the mother and one from the father; these are called the sex chromosomes. Mothers contribute an X and fathers an X or a Y, making the Y chromosome the primary determinant of a child's sex. Females are XX and males are XY, and this genetic fact occurs at the moment of conception.


FIGURE 5.3 A normal set of chromosomes. The first 22 pairs are matched, but the last pair (the sex chromosomes) does not match, indicating the person carrying these chromosomes is male.
© Biophoto Associates/Photo Researchers/Science Source
Abnormalities sometimes occur in the sex chromosomes; the two most common disorders of sex chromosomes—also known as intersex conditions—are Klinefelter syndrome and Turner syndrome. Klinefelter syndrome, a condition in which a male carries two or more X chromosomes in addition to the Y chromosome, occurs in about 1 in 1000 males and causes infertility and underdeveloped genitalia. Turner syndrome occurs in about 1 in 2500 females. Women with Turner have only a single complete X chromosome. People with this condition will need technological assistance to have children and can sometimes have other medical problems.Page 116

Genetic sex dictates whether the undifferentiated gonads become ovaries or testes. If a Y chromosome is present, the gonads become testes and produce the male hormone testosterone. Testosterone circulates throughout the body and causes the undifferentiated reproductive structures to develop into male sex organs (e.g., penis and scrotum). If the chromosomal arrangement is XX, the gonads become ovaries and the genital structures develop into a vagina, clitoris, and labia. Some researchers believe that this process, often referred to as sexual differentiation, is influenced solely by the presence or absence of testosterone. Others, however, believe that the relationships among chromosomes, genes, and hormones are far more complex, and that intersex conditions are a natural variation of these complicated and not always binary processes.

Exposure to hormones affects more than the sexual organs: It also influences development of the brain. Some research in this area has suggested that males tend to perform better than females at tasks requiring spatial skills, and that females perform better than males on tests of verbal skills. Proponents of this research posit that androgens are involved in this gender difference because genetic females who are exposed to androgens sometimes perform better at spatial skills and genetic males deprived of these hormones do worse. There are many criticisms of this research, however, because it is very difficult to separate the ways that boys and girls are treated—even infants—from the effects of biological hormones on their abilities.

What is important to keep in mind is that each person is a combination of biological, environmental, and culturalPage 117 events. Biology acts on the cells in the body, including the brain. The physical and social environment then shapes this biological foundation to produce unique individuals. Some researchers point to the human past as a way to explain sex differences in language and visual-spatial skills. For example, the early division of labor with men as hunters and women as food gatherers, camp organizers, and child raisers may have promoted the development of different skills based on gender, including visual-spatial skills in men and communication skills in women. Some researchers argue that men and women are still socialized into distinct gender roles, and that this plays a significant role in how their brains develop over time.


Once they reach puberty, adolescents are biologically adults, but it will take several more years for them to become adults in social and psychological terms.
© Cathy Yeulet/123RF
Female Sexual Maturation

Although humans are typically sexually differentiated at birth, the differences between males and females are accentuated at puberty, the period during which the reproductive system matures, secondary sex characteristics develop, and the bodies of males and females begin to appear more distinctive (while still overlapping in many ways). The changes of puberty are induced by testosterone in the male and estrogen and progesterone in the female.

Puberty in Females

The first sign of puberty in girls is often breast development, followed by a rounding of the hips and buttocks. As the breasts develop, hair appears in the pubic region and later in the underarms. Shortly after the onset of breast development, girls show an increase in growth rate. Breast development usually begins between ages 8 and 13, and the time of rapid body growth occurs between ages 9 and 15.Page 118

The Menstrual Cycle

A major landmark of puberty for most young women is the onset of the menstrual cycle, the monthly ovarian cycle that leads to menstruation (loss of blood and tissue lining the uterus) in the absence of pregnancy. The timing of menarche (the first menstrual period) varies with several factors, including race/ethnicity, genetics, and nutritional status. The "normal" range for the onset of menstruation is wide; some girls experience menarche as young as 9 or 10, and others when they are 16 or 17 years old. The current average age of menarche in the United States is around 12½ years of age. Two hundred years ago, the average age of menarche was closer to 17 years. The earlier onset of menarche today is probably due in large part to nutritional factors. When age at menarche is examined worldwide, studies show that menarche tends to come later to girls who live in relative poverty with diets lacking in protein and calories. Obesity is strongly correlated with earlier menarche, which may explain the current trend for earlier menarche in the United States and many other countries. Some experts worry that exposure to estrogen-like chemicals in the environment, including estrogenized food, may also contribute to earlier menarche. Because it is the biological norm for women born with female sex organs to menstruate, girls should check with a health care provider if their menstrual cycle does not begin during their adolescence. Although it might be normal, it might also indicate a disease or other problem.

The day of the onset of bleeding is considered to be day 1 of the menstrual cycle. For the purposes of our discussion, a cycle of 28 days will be used; however, normal cycles vary in length from 21 to 35 days. The menstrual cycle consists of the following four phases (Figure 5.4):


FIGURE 5.4 The menstrual cycle.
Menses. During menses, characterized by the menstrual flow, blood levels of hormones from the ovaries and the pituitary gland are relatively low. This phase of the cycle usually lasts from day 1 to about day 5.
Estrogenic phase. The estrogenic phase begins when the menstrual flow ceases and the pituitary gland begins to produce increasing amounts of follicle-stimulating hormone (FSH) and luteinizing hormone (LH). Under the influence of FSH, an egg-containing ovarian follicle begins to mature, producing increasingly higher amounts of estrogen. Stimulated by estrogen, the endometrium (the uterine lining) thickens with large numbers of blood vessels and uterine glands.
Ovulation. A surge of a potent estrogen called estradiol from the follicle causes the pituitary gland to release a large burst of LH and a smaller amount of FSH. The high concentration of LH stimulates the developing follicle to release its ovum. This event is known as ovulation. After ovulation, the follicle is transformed into the corpus luteum, which produces progesterone and estrogen. Ovulation theoretically occurs about 14 days prior to the onset of menstrual flow, with the window of greatest fertility occurring from a few days before ovulation to about one day after. This information has been used to attempt to predict the most fertile time during the menstrual cycle for fertility treatments and natural family planning methods (see Chapter 6). However, a recent study showed that even women with regular menstrual cycles often have unpredictable ovulation, and can actually be fertile on any day of the month, including during menstruation. The "window of fertility" is especially unpredictable in teenagers and women who are approaching menopause.
Progestational phase. During the progestational phase of the cycle, the amount of progesterone secreted from the corpus luteum increases and remains high until the onset of the next menses. Under the influence of estrogen and progesterone, the endometrium continues to develop, readying itself to receive and nourish a fertilized ovum. If pregnancy occurs, the fertilized egg produces the hormone human chorionic gonadotropin (hCG), Page 119which maintains the corpus luteum. Thus levels of ovarian hormones remain high and the uterine lining is preserved, preventing menses. hCG is the hormone detected by pregnancy tests.
If pregnancy does not occur, the corpus luteum degenerates, and estrogen and progesterone levels gradually fall. Below certain hormonal levels, the endometrium can no longer be maintained, and it begins to slough off, initiating menses. As the levels of ovarian hormones fall, a slight rise in LH and FSH occurs, and a new menstrual cycle begins.

QUICK STATS

75% of women experience premenstrual symptoms during their child-bearing years.

—National Institutes of Health, 2012
Menstrual Problems

Menstruation is a normal biological process, and physical or emotional symptoms associated with the menstrual cycle are common. Many women experience menstrual cramps, the severity of which tends to vary from cycle to cycle. Dysmenorrhea, discomfort associated with menstruation, can include any combination of the following symptoms: lower abdominal cramps, backache, vomiting, nausea, bloating, diarrhea, headache, and fatigue. Many of these symptoms can be attributed to uterine muscular contractions caused by chemicals called prostaglandins. Nonsteroidal anti-inflammatory drugs (NSAIDs) such as ibuprofen often relieve dysmenorrhea by blocking the effects of prostaglandins. Oral contraceptives are also effective in reducing dysmenorrheal symptoms in most women.

Many women experience transient emotional symptoms prior to the onset of their menstrual flow. Depending on their severity, these symptoms may be categorized along a continuum: premenstrual tension, premenstrual syndrome (PMS), and premenstrual dysphoric disorder (PMDD). Premenstrual tension symptoms are mild and may include negative mood changes and physical symptoms such as abdominal cramping and backache. More severe symptoms are classified as PMS; very severe symptoms that impair normal daily and social functioning are classified as PMDD. All three conditions share a definite pattern. Symptoms appear prior to the onset of menses and disappear within a few days after the start of menstruation. Premenstrual tension is quite common, PMS affects about 1 in 5 women, and PMDD affects fewer than 1 in 10 women.

Symptoms associated with PMS and PMDD can include breast tenderness, water retention (bloating), headache, fatigue, insomnia or excessive sleep, appetite changes, food cravings, irritability, anger, increased interpersonal conflict, depression, anxiety, tearfulness, inability to concentrate, social withdrawal, and the sense of being out of control or overwhelmed.

Despite many research studies, the causes of PMS and PMDD are still unknown, and it is unclear why some women are more vulnerable than others. These conditions are especially tricky to research because the symptoms overlap with many other conditions, and they are also normal responses to stress, which is common. Research has focused on a variety of substances in the body that may fluctuate with the menstrual cycle. Most researchers agree that PMS is probably caused by a combination of hormonal, neurological, genetic, dietary, and psychological factors.

The following strategies provide relief for many women with premenstrual symptoms, and all of them can contribute to a healthy lifestyle at any time:

Limit salt intake. Salt promotes water retention and bloating.
Exercise. Women who exercise may experience fewer symptoms before and after menstrual periods.
Don't use alcohol or tobacco. Alcohol and tobacco may aggravate certain symptoms of PMS and PMDD.
Eat a nutritious diet. Choose a low-fat diet rich in complex carbohydrates from vegetables; fruits; and whole-grain breads, cereals, and pasta. Get enough calcium from calcium-rich foods and, if needed, supplements. Minimize your intake of sugar and caffeine, and avoid chocolate, which is rich in both.
Relax. Stress reduction is always beneficial, and stressful events can trigger PMS symptoms. Try relaxation techniques during the premenstrual time. Orgasms, including those from masturbation, can also help reduce stress and relieve cramping.
If you suffer persistent premenstrual symptoms, keep a daily diary to track the types of symptoms, their severity, and their correlation with your menstrual cycle. Some women find help after being evaluated by a health care provider.

Selective serotonin reuptake inhibitors (SSRIs), such as Prozac and Zoloft, are sometimes used to treat PMS and PMDD. Until recently, women using SSRIs took the medication throughout the entire menstrual cycle, but taking the medication during just the progestational phase of the cycle is effective in some women. However, these medications are not without side effects and may negatively affect sexual functioning—specifically causing low desire as well as difficulty with arousal and attaining orgasm.Page 120

Other drug treatments for PMS and PMDD include certain oral contraceptives, diuretics to minimize water retention, and NSAIDs such as ibuprofen. A number of vitamins, minerals, and other dietary supplements have also been studied for PMS relief. Only one supplement, calcium, has been shown to provide relief in rigorous clinical studies; several others show promise, but more research is needed.

Male Sexual Maturation

Reproductive maturation of boys occurs about two years later than that of girls; it usually begins at about age 10 or 11 (Figure 5.5). Testicular growth is usually the first obvious sign of sexual maturity in boys. The penis also grows at this time, reaching adult size by about age 18. Pubic hair starts to develop after the genitals begin increasing in size, with underarm and facial hair gradually appearing. Hair on the chest, back, and abdomen increases later in development. Facial hair often continues to get thicker and darker for several years after puberty. The voice deepens as a result of the lengthening and thickening of the vocal cords. A small amount of breast development occurs in many boys during puberty. This is called gynecomastia, and it usually decreases after puberty. Excessive breast growth can occur in some boys, especially if they are overweight.


FIGURE 5.5 Milestones in sexual maturation of girls and boys.
source: The Merck Manual Home Health Handbook, Online Version. © 2010-2013 Merck Sharpe & Dohme Corp., a subsidiary of Merck & Co., Inc., Whitehouse Station, NJ, USA (http://merckmanuals.com/home/childrens_health_issues/adolescents/physical_andsexual_development.html).
Boys grow taller for about six years after the first signs of puberty, with a rapid period of growth about two years after puberty starts. Largely because of the influence of testosterone, muscle development and bone density are much greater in males than in females. By adulthood, men, as a group, have one and a half times the lean body mass of women as a group, and nearly half the body fat. However, many individual men and women fall outside these averages.

Ask Yourself

QUESTIONS FOR CRITICAL THINKING AND REFLECTION
Think about your own experience as you matured during puberty and adolescence. In what ways did these changes affect your life? How did they contribute to the person you are today?
Aging and Human Sexuality

Hormone production and sexual functioning change as we age. Although sexual functioning may diminish as one ages, sexuality and sensuality can continue to be a source of great pleasure and satisfaction. A recent study of sexuality in older Americans found that three-fourths of 57- to 64-year-olds were sexually active (defined as having had at least one sexual partner in the past year). Half of those people aged 65-74, and about one-fourth of people aged 75-85, remained sexually active. People who remain healthy and active are much more likely to continue to be sexually active in their older years.

Menopause

As a woman approaches age 50, her ovaries gradually cease to function and she enters menopause, the Page 121cessation of menstruation (Table 5.1). For some women, the associated drop in hormone production causes troublesome symptoms. The most common physical symptom of menopause is the hot flash, a sensation of warmth rising to the face from the upper chest, with or without perspiration and chills. During a hot flash, skin temperature can rise by more than 10 degrees. Other menopausal symptoms can include vaginal dryness, low libido, painful intercourse, night sweats, insomnia, thinning of head hair, and mood changes. Osteoporosis—decreasing bone density—can develop, making older women more vulnerable to fractures.

Table 5.1 Reproductive Aging in Women
AGE*
SIGNS & SYMPTOMS—WHAT'S HAPPENING
STAGE OF REPRODUCTION
9-15
First period; variable menstrual cycles
Menarche; beginning reproductive years
16-30
Regular menstrual cycle; fertility peaking
Reproductive years
31-42
Regular menstrual cycle; fertility progressively declining
Reproductive years
Early 40s
Lengths of menstrual cycle vary increasingly
Menopausal transition
Late 40s-early 50s
Two or more skipped periods; hot flashes, irritability, and sleep disturbance; bone loss begins
Menopausal transition
45-55
Final period (i.e., no period for 12 months)
Menopause
50s and beyond
Vaginal dryness, bone loss. Hot flashes can persist (for a few women, into their 60s and 70s).
Postmenopause
*Women vary a great deal in the ages at which they go through these stages. The average length of menopause and the transition leading up to it is four years, but for some women symptoms may last only a few months, and for others, 10 years.

source: American Society for Reproductive Medicine. 2012. Reproductive Aging in Women (http://www.reproductivefacts.org).

Although sexual physiology changes as people get older, many men and women readily adjust to these alterations.
© Big Cheese Photo/360/Getty Images RF
As a result of decreased estrogen production during menopause, the vaginal walls become thin, and lubrication in response to sexual arousal can diminish. Sexual intercourse may become painful. Hormonal treatment or the use of lubricants during intercourse can minimize these problems.

Cross-cultural studies comparing Japanese with North American women dispel the idea that hot flashes and other menopausal reactions are universal. A diet of fish and vegetables; an exercise regimen of cycling, walking, or farming; and cultural ideas about the meaning of bodily changes positively affected the Japanese experience of menopause among the women studied.

In Western medicine, doctors once regularly prescribed estrogen for postmenopausal women to relieve hot flashes, vaginal dryness, bone loss, and a host of other symptoms in a regimen called hormone replacement therapy, or HRT. However, in the past several years, reanalysis of the data on potential side effects, which include cardiovascular disease, blood clots, and breast cancer, has resulted in more individualized approaches—including, for example, low-dose estrogen, sometimes in the form of a patch, cream, or vaginal ring, designed to treat specific symptoms of menopause and with a reduced risk of side effects. (See Chapters 12, 15, and 22 for more information about osteoporosis and heart disease.)

Aging Male Syndrome

Between the ages of 35 and 65, men experience a gradual decline in testosterone production, resulting in the aging male syndrome, sometimes referred to as male menopause or andropause. Some experts prefer the term aging male syndrome because the process is much more gradual than female menopause. Symptoms vary widely, but most men experience at least some of the followingPage 122 symptoms as they age: loss of muscle mass, increased fat mass, decreased sex drive, erectile problems, depressed mood, irritability, difficulties with concentration, increased urination, loss of bone mineral density, and sleep difficulties. In some cases, men who have low testosterone may benefit from carefully prescribed testosterone replacement therapy.

As men get older, they depend more on direct physical stimulation for sexual arousal. They take longer to achieve an erection and find it more difficult to maintain; orgasmic contractions are less intense. Older men with erectile dysfunction often use prescription medications that increase blood flow to the penis, resulting in a firmer erection.

Unlike women, who are born with all the eggs they will ever have and stop being fertile at menopause, men continue to produce sperm throughout their lives and can sometimes father children well into their eighties and even nineties. Starting at about age 30, however, men become gradually less fertile. The pregnancy rate drops to 50% for couples with a man over age 35, regardless of the woman's age. Men over age 40 are more likely to produce children with health problems such as autism, schizophrenia, and Down syndrome.
GENDER ROLES AND SEXUAL ORIENTATION
As discussed in Chapters 2 and 4, your gender role is everything you do in your daily life that expresses your gender—your masculinity, femininity, or queerness—to others, including dress, speech patterns, and mannerisms. Parents often choose gender-specific names, clothes, and toys for their children, and children may model their own behavior after their same-gender parent. Family and friends create an environment that teaches the child how to act appropriately as a girl or a boy. Teachers, television, books, and even strangers model these gender roles. The concept of gender roles is intertwined with that of sexual orientation, a topic we also explore in this section.

Gender Roles

In general, gender is distinct from sex in that it refers to how people identify and feel about themselves, rather than the body parts and sexual organs they have. For example, a person who was born with a penis—and therefore assigned a male sex—may feel more like a girl or a woman than a man. They may also feel like neither, and identify as queer or genderqueer. As discussed earlier, some people who feel masculine or feminine but whose sex does not match their gender refer to themselves as transgender; people who identify as neither gender sometimes use the term gender nonconforming. Transgender individuals may be heterosexual, homosexual, bisexual, or asexual, or they may have any combination of sexual orientations. They are more likely to identify around the ways they do or don't feel like a woman, man, both, or neither than around who they feel attracted to, love, or want to have sex with.

Some people use the term androgyny to describe the state of being neither overtly male or female. Androgynous adults are less gender stereotyped in their thinking; in how they look, dress, and act; in how they divide work in the home; in how they think about jobs and careers; and in how they express themselves sexually.

The term cisgender describes people who do not feel transgender but who instead feel that the sex they were assigned at birth (usually male or female), and the gender they were raised with as a result, aligns with the way they feel about themselves. A cisgender woman, for example, would likely have been born with female sexual organs and genitals, would have been raised as a girl, and experiences herself as a woman.

Transsexual is a term that describes transgender people who seek sex reassignment, which involves hormonalPage 129 treatments to induce secondary sex characteristics such as breasts or facial hair, and/or surgery to change the appearance of the genitals or breasts. People who were born male and use surgery and other procedures to fully transition to being a woman are sometimes called male-to-female transsexuals. People born female who undergo surgery and procedures to become men are called female-to-male transsexuals.

A girl works as a bicycle mechanic.
Our sense of gender is shaped by cultural factors. Gender stereotypes can limit career aspirations, but awareness can help counter stereotypes, broaden occupational choices, and provide opportunities for everyone to pursue individual goals.
© Todor Tsvetkov/Getty Images
Not all transgender people desire surgical or hormonal treatment but still wish to live in another gender. These people might also use the terms trans woman (male-to-female transition) or trans man (female-to-male transition).

In contrast, the term transvestite refers to a person, usually a man, who enjoys wearing clothing identified with another gender. Cross-dressing covers a broad range of behaviors, from wearing one article of clothing associated with another sex in a private location to wearing an entire outfit in public. Though once thought to be gay men, the majority of transvestites are heterosexual, married men.

Transgender children may, from an early age, show intense and persistent distress about their sex and may behave and view themselves as another sex. Some of these children may be diagnosed with gender incongruence, and some may be given medications to slow or delay the potentially distressing bodily changes associated with puberty.

Gender roles vary from one time to another and from one society to another. In Denmark today, for example, women may take 4 weeks of maternity leave before the expected birth of their child and 14 weeks afterward. Men may take 2 weeks of paternity leave, and then both parents together may share 32 weeks of parental leave, sometimes with full pay. In the United States, no federal provision for paternity leave exists, and mothers are provided only 12 weeks of maternity leave, with no pay. (Time off with compensation is offered by many employers and three individual states.) These disparities powerfully communicate the beliefs these societies hold regarding the roles men and women should play in parenthood. The fact that gender roles differ for different groups tells us that the roles are learned behaviors that can be changed.

QUICK STATS

Almost three times as many women (17.4%) as men (6.2%) aged 18-44 reported any same-sex contact in their lifetime.

—National Health Statistics Report, 2016
Sexual Orientation

Sexual orientation refers to the person or people you are emotionally connected to (love), romantically attached to (relationship), sexually attracted to (desire), and behaviorally intimate with (sex). For many people, the pattern is consistent, exclusively heterosexual or exclusively homosexual for all categories: love, relationship, desire, and sex. For others, there may be more variation. As indicated, sexual orientation exists along a continuum that ranges from exclusive heterosexuality (attraction to people of the other sex) through bisexuality (attraction to people of both sexes) to exclusive homosexuality (attraction to people of your own sex) to asexuality (lack of sexual attraction to others). The terms straight and gay are often used to refer to heterosexuals and homosexuals, respectively, and female homosexuals are also referred to as lesbians. As mentioned earlier, in recent years the term queer has been reclaimed as a self-identifier by some elements of the gay community as well as by people who do not identify with conventional gender categories or with the gender they were assigned as children.

Sexual orientation involves feelings and self-concept, and individuals may or may not express their sexual orientation in their behavior. In national surveys, about 2-6% of men identify themselves as homosexuals and about 2% of women identify themselves as lesbians. Gauging the accuracy of these estimates is difficult because people may not tell the truth in surveys that probe sensitive and private aspects of their lives. In addition, people's expressed sexual orientations may be quite different from their actual sexual practices. For example, some people identify as heterosexual, but most of their sexual partners may be of their own sex.

Heterosexuality

A majority of people are heterosexual. Heterosexual relationships usually include all of the behavior and relationship patterns described in Chapter 4: dating, engagement, living together, and marriage.Page 130

Two women embrace each other.
This couple's physical experiences together will be powerfully affected by their emotions, ideas, values, and the quality of their relationship.
© jeffbergen/Getty Images
Homosexuality

Though homosexuality exists in all cultures, attitudes toward homosexuality vary tremendously. In some cultures, homosexual behavior is fully accepted; in others, it is tolerated but not encouraged. In some societies, homosexuality is illegal and can be punished severely, even by death. Homosexual individuals are as varied and different from one another as heterosexuals are. Just like heterosexuals, lesbians and gay men may be in long-term, committed relationships, or they may date different people. And, as of 2016, same-sex couples can marry in more than 20 countries, including the United States.

Bisexuality

Because many experts believe that human sexuality exists on a spectrum, they also believe that many of us are potentially bisexual. However, only a relatively small number of people are more or less equally attracted to both men and women. In the United States, fewer than 5% of men and women identify themselves as bisexual. Some observers think bisexuals are confused and do not know if they like men or women; however, most bisexuals are clear they like both men and women.

The Origins of Sexual Orientation

Many theories try to account for the development of sexual orientation. At this time, most experts agree that sexual orientation results from multiple genetic, hormonal, cultural, social, and psychological factors. Many people report being aware of their gender identity and sexual orientation early in life, long before they became sexually active, and most do not feel they had a choice in their sexual orientation. The majority of experts agree that conscious choice is not usually a factor in whether someone is gay, straight, or queer.

Some scientists, however, continue to look for genetic markers associated with sexual orientation in males. Twin studies are one way of looking at the genetic contribution to sexual identity. Identical twins share the same DNA, so if sexual orientation were entirely genetically determined, we would expect that if one identical twin were homosexual, the other would be as well. But studies of many identical male twins show that if one twin is gay, there is only a 50-52% chance that the other twin will have the same sexual orientation. When we consider fraternal twins, who share fewer genes, the chances decrease to 22%. Two adopted children, who share an environment but no genetic makeup, have an 11% chance that both will be gay. According to these studies, the less genetic makeup two family members share, the less likely that, if one is gay, the other will be as well. Not all scientists who study this issue come to the same conclusions, however, and it is more difficult to make a genetic connection when looking at females, suggesting that female sexuality may differ from male sexuality. These studies provide evidence that our genes, while not wholly responsible for our sexual orientation, may contribute to it.

Exposure to hormones before birth may have an impact on sexual orientation. Experiments with mice show that exposure to sex hormones early in development determines whether they will ultimately be sexually attracted to male or female mice. Sexuality is far more complicated in human beings, but some researchers believe that the hormonal environment in the womb has an influence on sexual orientation.

Many psychological theories have been proposed to explain the development of heterosexual or homosexual sexual orientation. Researchers have looked at how much contact children have with men and women, at the types of relationships children have with their parents, and at family dynamics. Early negative experiences with heterosexuality or positive experiences with homosexuality have also been proposed as possible influences. The significant growth of single-parent families over the past 40 years has not been accompanied by large shifts in sexual orientation among Americans, so it is unlikely that family dynamics or early learning experiences are strong factors in determining sexual orientation. In addition, parents' sexual orientation seems to have little impact on children's sexual orientation. Studies of children raised by gay or lesbian parents show that these children's ultimate sexual orientation is similar to that of children raised by heterosexual parents. In addition, most people who identify as gay or lesbian had heterosexual parents.

So far, most studies on the origin of sexual orientation have focused on males. The factors that determine sexual orientation in women may be even more complex. Although genes appear to be one likely determinant of sexual orientation, further research is required to fully understand the complex interactions that exist.
SEXUAL BEHAVIOR
A wide variety of behaviors stem from sexual impulses, and sexual expression takes a variety of forms. For some people, the most basic aspect of sexuality is reproduction; for others, sex is more about fun and pleasure than having children. In general, sexual excitement and satisfaction are aspects of sexual behavior separate from reproduction, and thePage 131 intensely pleasurable sensations of arousal and orgasm are some of the strongest motivators for human sexual behavior. People are infinitely varied in the ways they seek to experience erotic pleasure.

Not all people experience sexual pleasure in the same way. Asexual is the term used to describe people who do not experience sexual desire but who may still enjoy being in romantic and other close relationships. Some asexual people, called demisexuals, experience sexual attraction only to people with whom they feel an intimate or loving bond.

QUICK STATS

Between 0.5% and 1.0% of the U.S. population is estimated to be asexual.

—Canadian Journal of Human Sexuality, 2014
The Development of Sexual Behavior

Sexual behavior is a product of many factors, including genetics, physiology, psychology, and social and cultural influences. Our behavior is shaped by the interplay of our biological predispositions and our life experiences.

Gender, Sexuality, and the Mass Media

Many of our ideas about sexuality and gender roles are shaped by the mass media. Media images of sexuality can be as influential as family in shaping individuals' sexual attitudes and behaviors. Yet these images are often unrealistic and help perpetuate sexual stereotypes in our society. For example, the mass media rarely portray people negotiating safer sex or communicating seriously about other sexual issues.

Childhood Sexual Behavior

The capacity to respond sexually is present at birth. Ultrasound studies suggest that boys experience erections in the uterus. After birth, both sexes have the capacity for orgasm, though many babies may not experience it. Baby boys will experience erections and baby girls experience vaginal lubrication. As children grow, many discover this capacity through self-exploration. Sexual behaviors gradually emerge in childhood; self-exploration and touching the genitals are common forms of play, observed among infants as young as six months. They gradually lead to more deliberate forms of masturbation, with or without orgasm.

Children often engage in sexual play with playmates by exploring each other's genitals. These activities are often part of games like "playing house" or "playing doctor." By age 12, 40% of boys have engaged in sex play. The peak exploration age for girls is 9, by which time 14% have had such experiences.

Adolescent Sexuality

A person who has experienced puberty is biologically becoming an adult. But in psychological and social terms, people take 5-10 more years to attain full adult status. This discrepancy between biological and social maturity creates considerable confusion over what constitutes appropriate sexual behavior during adolescence. Most countries have laws regarding the age at which someone is deemed old enough to make the decision to have sexual intercourse (the "age of consent"). Sex below that age is illegal, even if the young person agrees willingly. In the United States, the age of consent varies between ages 16 and 18, depending on the state.

Sexual fantasies and dreams become more common and explicit in adolescence than at earlier ages, often as an accompaniment to masturbation. Research has shown that about 80% of teenage boys and 55% of teenage girls masturbate more or less regularly. Once puberty is reached, orgasm inPage 132 boys is accompanied by ejaculation. Teenage boys also experience nocturnal emissions ("wet dreams"). Some girls also have orgasmic dreams.


The mass media often portray young Americans as sexual athletes, who frequently engage in casual sex with many partners. Such characters are seldom shown discussing safer sex practices.
© Stockbyte/PunchStock RF
Sexual activity refers to more than intercourse and includes a variety of behaviors and stimulation. Sexual interaction during adolescence usually takes place between peers in the context of dating or partying. Sexual intimacy is often expressed through kissing, caressing, and stimulating the breasts and genitals. Although these activities lead to arousal, they don't always result in orgasm.

In addition to the above behaviors, many American teenagers also engage in sexual intercourse. According to a recent report, nearly half of heterosexual high school students have engaged in intercourse. Rates for premarital sex vary considerably from one group to another, based on racial, ethnic, educational, socioeconomic, religious, geographic, and many other factors. First-time intercourse is affected by these same factors, plus psychological readiness, fear of consequences, being in love, sexual orientation, going steady, peer pressure, and the desire to act like an adult, gain popularity, or rebel. Family relationships and attitudes toward sex influence teen sexual behavior. Additionally, a teen's perception of what is "normal" among peers has a strong influence on his or her choices about sex. Fears of pregnancy and the pressure to maintain one's virginity lead many teenagers to engage in forms of oral and anal sex that they do not believe are real "sex." These behaviors can have emotional, social, and medical consequences in that they can lead to a sexually transmitted infection; and they can generate many of the same feelings of intimacy, rejection, and confusion that come with vaginal intercourse.

Adolescents can also be the perpetrators and victims of sexual assault and violence, including rape. Having sex with someone without his or her consent, whether or not violence is used and whether or not the people involved know one another, constitutes sexual assault. This topic is discussed further in Chapter 21.

Beginning in childhood, sex play involves members of one's own sex as well as of the other sex. Same-sex attractions, with or without sexual encounters, are common in adolescence and are not always necessarily related to adult sexual orientation. Many adult gay men and women, however, recall same-sex attractions in childhood.

QUICK STATS

The average age at first sexual intercourse in the United States is about 17 years old.

—Centers for Disease Control and Prevention, 2015
Adult Sexuality

Early adulthood is a time when people make important life choices—a time of increasing responsibility in terms of interpersonal relationships and family life. In recent years the trend has been toward marriage at a later age than in past decades. The average age at marriage in the United States is 28-29 for men and 27-29 for women. People with advanced educational degrees often delay marriage until their thirties. According to the Kinsey Institute, men are typically sexually active for 10 years before getting married, and women for 8 years. Today more people in their twenties believe that becoming sexually experienced rather than preserving virginity is an important prelude to selecting a mate. (See the box "Questions to Ask Before Engaging in a Sexual Relationship.")

WELLNESS ON CAMPUS: Questions to Ask Before Engaging in a Sexual Relationship

Who Am I Sexually Attracted To?
What are the characteristics that usually attract me to someone in a physical way?
How comfortable am I with the people I find sexually attractive? What would I change if I could? Do I feel safe when I am with them?
Are the people I am usually sexually attracted to the same types of people with whom I could envision having a long-term, stable relationship? Why or why not?
What Sexual Behaviors are Comfortable for Me Right Now?
What has influenced my comfort level with these behaviors?
What am I not entirely comfortable with, but would be willing to experiment with in order to please a partner? What level of trust would I need to establish with that partner in order to proceed? What would we need to talk about ahead of time?
What exactly do I say in order to make my comfort level clear to my partner? What do I do if my partner tries to push me beyond my comfort level?
How Can I Express My Sexual Needs, Desires, and Concerns To a Potential Sexual Partner?
When would be the best time to talk about these needs, desires, and concerns?
How do I start the conversation?
What will I do if my needs are not being met or my concerns are not taken seriously?
What Preparations Do I Need To Make in Order To Engage in the Safest Sex Possible?
If I am engaging in heterosexual sexual activity, and I do not wish to reproduce, I need to obtain birth control. Have I consulted a health professional to figure out the best method of birth control for myself and my partner? Do I know how to employ this method correctly? Have we discussed what we plan to do if a pregnancy occurs?
If I am engaging in any type of sexual activity with a partner, I need protection from sexually transmitted infections. Have I consulted a health professional to figure out the best method of STI protection for myself and my partner? Do I know how to employ this method correctly? Have I discussed with my partner his or her sexual history, including information about risky behavior and STIs? Do I understand the ways that sexual behaviors transmit these infections?
What do I need from my partner in order to ensure that I feel emotionally safe before, during, and after our sexual behavior together?
Do I engage in any behaviors that cause me to participate in sexual activity that I wouldn't otherwise be comfortable with, such as excessive drinking or drug use? What do I need to do in order to reduce or eliminate these behaviors?
Do I make sure that the people with whom I am being sexual are actively consenting to the behaviors? Do I understand what constitutes sexual consent? Do I understand that I need to stop what I'm doing if the other person asks me to or is not communicating active and willing consent?
Films, television, and other media sources project the image that everyone is having sex, with many partners. On average, though, men aged 30-44 report a total of six to eight female sexual partners; women in the same age range report three to four male sexual partners. Only 21.6% of males and 9% of females report having more than 15 partners. Individual motivations for engaging in sexual activities change with age. Younger men state that they engage in sex for physical reasons, whereas women of the same age state that they engage in sex for emotional reasons. As men and women get older, their motives change; men more often engage in sex for emotional reasons, and women more often for physical reasons. This is to say that people of all kinds have sex for all kinds of reasons, all of which make sense to them at the time. In addition to age, many factors such as race, ethnicity, educational attainment, and living arrangements also influence adult choices about sexuality.

Sexuality in Illness and Disability

Any disease or disability that affects mobility, well-being, self-esteem, or body image has the potential to affect sexual expression. People with chronic diseases or disabilities often have special needs regarding their sexual behavior. They may also confront the perception that they are asexual or have lost themselves as the sexual person they once knew. Sexuality is integral to many of us, regardless of our physical status.

Ask Yourself

QUESTIONS FOR CRITICAL THINKING AND REFLECTION
How did your romantic and sexual relationships (or lack thereof) during adolescence influence how you felt about yourself? What influenced your beliefs about what sex would be like? Were your first sexual experiences what you expected? What misconceptions did you have about sex during adolescence? When and how were they corrected? Whether you are straight, gay, lesbian, or asexual, how and when did you become aware of your sexual orientation?
Page 133
Varieties of Human Sexual Behavior

Some sexual behaviors are aimed at self-stimulation only, whereas other practices involve interaction with one or more partners (see the box "Questions to Ask Before Engaging in a Sexual Relationship").. Some people feel sexual but choose not to express it, and some people do not feel any form of sexual desire.

Celibacy

Continuous abstention from sexual activities, called celibacy, can be a conscious and deliberate choice, or it can be necessitated by circumstances. Health considerations and religious and moral beliefs may lead some people to celibacy, particularly until marriage or until an acceptable partner appears.

Many people use the related term abstinence to refer to avoidance of just one sexual activity—intercourse. However, even if individuals abstain from intercourse, they may still put themselves at risk for STIs if they engage in other sexual behaviors. The use of abstinence to prevent pregnancy and STIs is discussed in Chapters 6 and 18. Celibacy and abstinence are not the same thing as asexuality because many people who identify as asexual engage in sexual activity with the people they love and feel close to. Asexuality refers to a lack of sexual desire, but not an avoidance of sexual behavior.

Autoeroticism

The most common sexual behavior for humans is masturbation. Masturbation is one form of autoeroticism; another is erotic fantasy, or creating imaginary experiences that range from fleeting thoughts to elaboratePage 134 scenarios. Orgasms originate in our brain as it gives meaning to stimulation and pleasure. Using functional MRI (fMRI) scans to map orgasms in the brain, researchers at Rutgers University found that at the time of orgasm every part of our brain lights up and is engaged. No other activity produces the same brain response.

Masturbation involves manually stimulating the genitals, rubbing them against objects, or using stimulating devices such as vibrators or masturbation sleeves. Although commonly associated with adolescence, masturbation is practiced by many throughout adult life. It may be used as a substitute for sexual activity or may include a partner. Women especially find that if they are stimulating their clitoris during penetration with a partner, they are more likely to experience orgasm. Masturbation gives a person control over the pace, time, and method of sexual release and pleasure.

QUICK STATS

79 million sexually active adults have contracted HPV, and nearly 1 in 6 people aged 14 to 49 years have genital herpes.

—Centers for Disease Control and Prevention, 2016
Touching and Foreplay

For many people, touching is integral to sexual experiences, whether in the form of massage, kissing, fondling, or holding. The entire body surface is a sensory organ, and touching almost anywhere can enhance intimacy and sexual arousal. Touching can convey a variety of messages, including affection, comfort, and a desire for further sexual contact.

During arousal, many partners manually and orally stimulate each other by touching, stroking, and caressing their partner's genitals. People vary greatly in their preferences for the type, pace, and vigor of such foreplay. Working out the details to accommodate each other's pleasure is a key to enjoying these activities. Direct communication about preferences can enhance sexual pleasure and protect both partners from physical and psychological discomfort. There is no correct order in which to engage in sexual activity, and these behaviors can also be engaged in instead of or after penetrative intercourse.

Oral-Genital Stimulation

Cunnilingus (the stimulation of the female genitals with the lips and tongue) and fellatio (the stimulation of the penis with the mouth) are common practices. Oral sex may be practiced either as part of foreplay or as a sex act culminating in orgasm. Although prevalence varies in different populations, 90% of men, 88% of women, and more than 50% of teens report that they have engaged in oral sex. A recent study showed that more teens aged 15-19 had engaged in oral sex than had engaged in vaginal intercourse. The most common reasons given for postponing vaginal sex were avoidance of pregnancy, the desire to remain technically a virgin, and the avoidance of STIs. Many people have the incorrect belief that they cannot acquire an STI during oral sex. Numerous STIs, including HIV, herpes, HPV, gonorrhea, chlamydia, and syphilis, can be transmitted through oral sex (see Chapter 18). Some studies show that people who report having oral sex are usually talking about fellatio and not cunnilingus, and many women report that male partners are reluctant to orally stimulate their genitals. This is one reason why many women find it difficult to have regular orgasms during heterosexual encounters.

Like all acts of sexual expression between two people, oral sex requires the cooperation and consent of both partners. If they disagree about its acceptability, they need to discuss their feelings and try to reach a mutually pleasing solution.

Anal Intercourse

About 36% of males and 31% of women, heterosexual and homosexual, report having engaged in anal sex. Some men and women find they are able to achieve orgasm through anal sex. Males who are being penetrated, either by a penis, finger, or sex toy, may find this induces orgasm because stimulation to the prostate may cause an ejaculation. This stimulation is often referred to as "milking the prostate" or prostate massage.

Because the anus is composed of delicate tissues that tear easily with friction, anal intercourse can be one of the riskiest of sexual behaviors for the transmission of HIV and all other STIs. If people are monogamous, up to date with their STI status, or use barrier devices such as condoms, the risk becomes lower. The use of condoms is highly recommended for anyone engaging in anal sex. Special care and precaution should be exercised if anal sex is practiced—cleanliness, lubrication, and gentle entry at the very least. Among women, anything inserted into the anus should not subsequently be put into the vagina unless it has been washed thoroughly. Bacteria normally present in the anus can cause vaginal infections, as well as urinary tract infections.

Sexual Intercourse

Men and women engage in vaginal intercourse for a variety of reasons, including to fulfill sexual and psychological needs and to reproduce. Among adults aged 18-44, 92% of men and 94% of women report having had vaginal intercourse. The most common heterosexual practice involves the man inserting his erect penis into the woman's lubricated vagina after sufficient arousal.

Much has been written on how to enhance pleasure through various coital techniques, positions, and practices. For a woman, the key factor in physical readiness for coitusPage 135 is adequate vaginal lubrication, and in psychological readiness, being aroused and receptive. For a man, the setting and the partner must arouse him to attain and maintain an erection. For many people, psychological factors and the quality of the relationship are more important to overall sexual satisfaction than sophisticated or exotic sexual techniques.

The use of force and coercion in sexual relationships is one of the most serious problems in human interactions. The most extreme manifestation of sexual coercion—forcing a person to submit to another's sexual desires—is rape, but sexual coercion occurs in many subtler forms, such as sexual harassment.

Commercial Sex

Conflicting feelings about sexuality are apparent in the attitudes of Americans toward commercial sex: prostitution and sexually oriented materials in a variety of formats. Prostitution is illegal in most of the United States, but penalties and general social disapproval have failed to eliminate it. Pornography is readily available and widely viewed in our society, although many people are concerned about its ubiquitous nature and the blurring of pornography with popular culture.

Pornography

Derived from the Greek word meaning "the writing of prostitutes," pornography (porn) is now often defined as obscene literature, art, or movies. A major problem in identifying pornographic material is that people and communities differ about what is obscene, as obscenity is typically a judgment by someone who finds it offensive. Differing definitions of obscenity have led to many legal battles over potentially pornographic materials. Currently the sale and rental of pornographic materials is restricted so that only adults can legally obtain them; however, the Internet is difficult to regulate, and many minors may have access to pornographic materials online. Child pornography—showing children who are not 18 years old naked and/or in sexual acts—is illegal.

Many people distinguish between "soft-core porn" and "hard-core porn" materials. Soft-core porn, often marketed for couples, typically includes an apparently loving couple having sex in a relaxed setting. There is mutual kissing and touching, and both partners are shown as having a positive experience. In hard-core porn, there is usually less mutual touching. Hard-core porn sometimes explicitly depicts sexual violence and exploitation. Hard-core porn materials tend to be the focus of more debate and disagreement than is the case for soft-core porn materials.

Much of the debate about pornography focuses on whether it is harmful. Some people argue that adults who want to view pornographic materials in the privacy of their own homes should be allowed to do so. Others feel that the exposure to explicit sexual material can lead to delinquent or criminal behavior, such as rape or the sexual abuse of children. Currently there is no reliable evidence that pornography by itself leads to violence or rape, and debate is likely to continue.

Online Porn and Cybersex

The appearance of thousands of sexually oriented websites has expanded the number of people with access to pornography, and it has made it more difficult for authorities to enforce laws regarding porn. People who might have hesitated to buy magazines or rent videos in person can now access sexually explicit materials online. Of special concern is the increased availability of child pornography, which previously could be acquired only with great difficulty and at great legal risk. Online porn is now a multibillion-dollar industry.

In addition to (or instead of) viewing porn online, hundreds of thousands of people also use the Internet to engage in cybersex, or virtual sex. Cybersex is erotic interaction between people who are communicating over the Internet. People can engage in cybersex in many ways, such as by visiting sexually oriented websites, joining cybersex chat rooms, participating in videoconferences via web cams, or even exchanging e-mail messages. Participants may have sexually explicit discussions, share private photographs, or engage in fantasy role-playing online. Many cybersex participants report feeling some degree of sexual excitement; some masturbate while viewing erotic images online or engaging in sexual chat. Online sex is an excellent way for people who have difficulty meeting partners, for economic, psychological, or physical reasons, to meet others and maintain relationships. It is also, for many people, a fun and novel way of expressing their sexuality.

Although many people view cybersex as a safe form of sexual expression, it is not without problems. It can be addictive, and some cybersex addicts report spending more than 50 hours a week online for sexual purposes. People who become addicted to cybersex or viewing online porn may become isolated and perform poorly at work or school. Their addiction may also have a negative impact on their interpersonal relationships.Page 136

"Sexting," sending provocative photos from cell phone to cell phone, has become popular, sometimes with serious consequences. Images can end up traveling from person to person by cell phone and from there onto social networking websites. These images can haunt individuals years later when they are viewed by potential employers or partners. Some teens have found themselves charged with child pornography and have even faced jail time as a result of forwarding a sexually explicit photo of an underage person to a friend. Teens who have found pictures of themselves engaging in sexual activity posted or shared online have faced adverse effects. Some have even committed suicide.

Prostitution

The exchange of sexual services for money is prostitution, also called sex work. Sex workers may be men, women (including trans men and women), or children, and the buyer of their services is nearly always a man, most of whom are white, middle class, middle aged, and married. Except in parts of Nevada, prostitution is illegal in the United States.

Purchasing sex can offer someone physical release without having to confront some of the more complicated aspects of sex: commitment, an expectation of intimacy, or a fear of rejection. Some people patronize prostitutes in order to have sex with a different type of partner than usual or to engage in a type of sex in which their usual partner is uninterested.

Sex workers come from a variety of backgrounds, and, like everyone who participates in the labor force, they are economically (rather than sexually) motivated. Many people who have sex for money lack the skills and education to engage in other forms of work, and they view their bodies as their most marketable asset. Many, though not all, report having been sexually abused as children; some begin as runaways who are escaping abusive homes and turn to prostitution as a way to survive. Queer and transgender people who have had to leave homes that do not accept their identities sometimes engage in sex work for these reasons.

Although many sex workers routinely use condoms with their clients, HIV infection and other STIs are still a concern. Some sex workers are injection drug users, and some have customers who are, contributing to a rate of HIV infection among this population that can be as high as 25-50%.

Ask Yourself

QUESTIONS FOR CRITICAL THINKING AND REFLECTION
What do you consider to be appropriate, moral sexual behavior? What behaviors do you think are inappropriate or immoral? What experiences have shaped your views of such behaviors? Have they changed in the past five years? What do you think they will be like five years from now?
Responsible Sexual Behavior

Healthy sexuality is an important part of adult life. It can be a source of pleasurable experiences and emotions and an important part of intimate partnerships. But sexual behavior also carries many responsibilities, as well as potential consequences such as pregnancy, STIs, and emotional changes in the relationship. Every sexually active person should be aware of these consequences and accept responsibility for them. Consider the following with your partners:

Open, Honest Communication

Each partner needs to clearly indicate what sexual involvement means to them. Does it mean love, fun, a permanent commitment, or something else? The intentions of both partners should be clear. For strategies on talking about sexual issues with your partner, see the box "Communicating about Sexuality."

TAKE CHARGE: Communicating about Sexuality

To talk with your partner about sexuality, follow the general suggestions for effective communication in Chapter 4. Getting started may be the most difficult part. Some people feel more comfortable if they begin by talking about talking—that is, initiating a discussion about why people are so uncomfortable talking about sexuality. Talking about sexual histories—how partners first learned about sex or how family and cultural background influenced sexual values and attitudes—is another way to get started. Reading about sex can also be a good beginning: Partners can read an article or book and then discuss their reactions.

Be honest about what you feel and what you want from your partner. Cultural and personal obstacles to discussing sexual subjects can be difficult to overcome, but self-disclosure is important for successful relationships. Research indicates that when one partner openly discusses attitudes and feelings, the other partner is more likely to do the same. If your partner seems hesitant to open up, try asking open-ended or either/or questions: "Where do you like to be touched?" or "Would you like to talk about this now or wait until later?"

If something is bothering you about your sexual relationship, choose a good time to initiate a discussion with your partner. Be specific and direct but also tactful. Focus on what you actually observe rather than on what you think the behavior means. "You didn't touch or hug me when your friends were around" is an observation. "You're ashamed of me around your friends" is an inference about your partner's feelings. Try focusing on a specific behavior that concerns you rather than on the person as a whole—your partner can change behaviors but not his or her entire personality. For example, you could say, "I'd like you to take a few minutes away from studying to kiss me" instead of "You're so caught up in your work, you never have time for me."

If you are going to make a statement that your partner may interpret as criticism, try mixing it with something positive: "I love being with you, but I feel annoyed when you...." Similarly, if your partner says something that upsets you, don't lash back. An aggressive response may make you feel better in the short run, but it will not help the communication process or the quality of the relationship.

If you want to say no to some sexual activity, say no unequivocally. Don't send mixed messages. If you are afraid of hurting your partner's feelings, offer an alternative if it's appropriate: "I am uncomfortable with that. How about...?"

If you're in love, you may think that the sexual aspects of a relationship will work out magically without discussion. However, partners who never talk about sex deny themselves the opportunity to increase their closeness and improve their relationship.
Agreed-On Sexual Activities

No one should pressure or coerce a partner. Sexual behaviors should be consistent with the sexual values, preferences, and comfort level of all partners. Everyone has the right to refuse sexual activity at any time, including married couples.

Sexual Privacy

Intimate relationships involving sexual activity are based on trust, and that trust can be violated if partners reveal private information about the relationship to others. Sexual privacy also involves respecting other people—not engaging in activities in the presence of others that would make them uncomfortable. The question of how to handle bringing a partner back to a shared dorm room is something that many college students must address. Roommates should be respectful of one another and discuss the situation in advance to avoid embarrassing encounters.

Safe Sex

Sexual partners should be aware of and practice safe sex to guard against STIs. Many sexual behaviors carry the risk of STIs, including HIV infection. Partners should be honest about their health and any medical conditions and work out a plan for protection. (For more information on STIs and safe sex practices, see Chapter 18.)

Contraception Use

If pregnancy is not desired, contraception should be used during sexual intercourse. Both partners need to take responsibility for protecting against unwanted pregnancy. Partners should discuss contraception before sexual involvement begins. (See Chapter 6 for more information about contraception.)

Sober Sex

The use of alcohol or drugs in sexual situations increases the risk of unplanned, unprotected sexual activity. Such consequences are particularly true for young adults, many of whom binge-drink during social events. The link between intoxication and unsafe sex is illustrated by a recent study that found states with higher drinking ages and higher beer taxes to have lower rates of STIs.

Binge drinking also increases the risk of sexual assault. About 20% of women in college experience sexual assault. Unfortunately, a cycle then ensues for some of these women: those with a history of sexual assault are then more likely to drink heavily. Approximately 30% of underage college women engage in such heavy episodic drinking, and women under age 21 also bear the highest risk for sexual assault in college. Alcohol and drugs impair judgment and should not be used in association with sexual activity. Be honest with yourself; if you need to drink in order to engage in sexual activities, maybe it's time to rethink your social life and relationships. As noted earlier, someone who is intoxicated cannot legally consent to sex.Page 137

Aside from the dangers of mixing alcohol and sex, alcohol typically impairs sexual performance. Although alcohol may lower sexual inhibition and make people more likely to attempt a sexual encounter, too much alcohol makes it difficult to achieve or keep an erection, decreases vaginal lubrication, and makes orgasm more difficult to achieve. Chronic overuse of alcohol reduces testosterone, ultimately causing erectile dysfunction, infertility, and body changes such as enlarged breasts in men. Women who overuse alcohol often experience menstrual abnormalities and decreased sexual function. Similarly, cigarette smoking has a powerful negative effect on sexual function, primarily because it decreases blood flow to the genitals.

Ask Yourself

QUESTIONS FOR CRITICAL THINKING AND REFLECTION
If you are sexually active or plan to become active soon, how open have you been in communicating with your partner? Are you aware of your partner's feelings about sex and about their comfort level with certain activities? Do you and your partner share the same views on contraception, STI prevention, and ethical issues about sex?
PREPARATION FOR PARENTHOOD
Before you decide whether or when to become a parent, you should consider your suitability and readiness. If you elect to have a child, there are actions you can take before the pregnancy begins to help ensure a healthy outcome for all.Page 185

Deciding to Become a Parent

Men and women alike should consider a number of factors when deciding whether to become parents. Some issues are relevant to both men and women; others apply only to women.

Health and Age

Generally speaking, healthier women tend to have more trouble-free pregnancies and healthier babies. Women considering motherhood should see their physicians for complete medical checkups to catch problems that can interfere with pregnancy or childbirth. For example, high blood pressure, diabetes, renal disease, cardiac disease, and rheumatologic disorders may require ongoing attention. If uncontrolled, these health problems can pose life-threatening dangers to a mother or child.

A mother's age and health can also be a factor in pregnancy and childbirth. Teenagers and women over age 35 have a higher incidence of certain problems that can affect the health of both mother and baby. In fact, most experts classify a pregnancy as "high risk" if the mother is a teenager or over age 35, especially if it is her first pregnancy.

Emotional Wellness

Just as they need to be physically prepared, parents also need to be emotionally ready to have a child. A new baby is totally helpless and relies on adults for everything. For parents, emotional preparedness means being strong and stable enough to handle the responsibility and being mature enough to give up certain freedoms in order to care for a child.

Relationships

The stress and expense of child rearing can strain any relationship, even a healthy one. This is why it is important for couples to plan for parenting. Through open, honest discussion, partners should make sure they are ready to take the step of having a child. Both should be equally committed to parenthood and agree on matters of child care, housework, and other day-to-day responsibilities. Couples with relationship problems should work together to resolve their issues—with professional help, if necessary—before adding a child to the mix.

New parents also need a strong support network of friends and family members who can lend a hand when things get tough. Many first-time parents count on their own parents and siblings for aid with child care or household chores. It can be easy, however, to alienate family and friends with too many requests for assistance. To avoid this problem, parents-to-be should include members of their support network in the planning process to figure out who will be able to help, in what ways, and at what times.

Financial Circumstances

Parenthood is financially draining, even for families with steady incomes and health insurance. According to a 2014 report from the U.S. Department of Agriculture, a two-parent, two-child family will spend between $9,130 and $25,700 per year per child, depending on where they live, subsidies, and the family's income level, to raise each child to age 18. Expenses increase significantly with each additional child.


A strong network of supportive friends and family makes parenting much easier.
© Monkey Business Images/Shutterstock
If you plan to have a child, you should be prepared financially—especially during the first few years, when the costs of diapers, furniture, pediatrician visits, and other necessities quickly add up. Expectant parents should also consider their larger financial picture, including taxes, insurance, and savings that are available for long-term goals and emergencies. People may choose to consult a qualified financial planner or explore online financial-planning resources.

Child care is an important expense to plan for, especially when both parents are working or in school full time. The cost and availability of such services can be a factor in determining whether parents can pursue their future plans. According to a 2015 report from Child Care Aware®, the yearly day care costs for an infant average from $4,822 in Mississippi to $22,631 in Washington, D.C.

QUICK STATS

Over 120,000 babies were born to mothers age 40 and over in 2015.

—National Center for Health Statistics, 2016
Preconception Care

The birth of a healthy baby depends in part on the mother's overall wellness before conception. The U.S. Public Health Service recommends that all women receive health care to help them prepare for pregnancy. Preconception care should include an assessment of health risks, the promotion of healthy lifestyle behaviors, and any treatments necessary to reduce risk. Following are some of the issues, Page 186tests, and treatments parents-to-be may encounter in preconception care:

Preexisting conditions. Medical conditions such as diabetes, cardiac and renal disease, epilepsy, asthma, psychiatric disease, and anemia can cause problems during pregnancy. Such conditions should be treated and monitored throughout pregnancy.
Medications. Some medications and dietary supplements harm the fetus, so a pregnant woman may need to change medications or stop taking certain drugs.
Prior pregnancies. Problems with previous pregnancies or deliveries—such as miscarriage, premature birth, or delivery complications—may be due to treatable physical conditions.
Age. A woman's age may place her at risk for certain problems during pregnancy. A pregnant teenager, for example, may require special nutrition to meet her own growing body's needs and those of her baby. All women should be offered genetic screening and diagnostic testing, depending on their risk assessment. Every patient has a baseline risk of 3% of having a fetal anomaly identified.
Tobacco, alcohol, and caffeine use. These substances can harm a developing fetus. Exposure to tobacco smoke may also harm the developing newborn. Women who smoke and drink should stop before becoming pregnant. Women who are pregnant or trying to conceive should limit their caffeine intake. (See Chapters 9-11 for more information about these and other substances.)
Infections. A woman who has any type of infection should be treated for the infection before getting pregnant to avoid passing infections to the baby. This is good advice for men, too, to avoid transmitting an infection to their partners. A woman may need to be vaccinated against hepatitis B, rubella (German measles), varicella (chicken pox), and other communicable diseases if she is at risk for them. Testing for tuberculosis and some sexually transmitted infections (STIs) can ensure treatment prior to pregnancy. (See Chapter 17 for more about infectious diseases.)
HIV. Any woman who is at risk of HIV infection should be tested before getting pregnant; her partner should be tested, too. If the woman tests positive, she should start on anti-retroviral medications in pregnancy to reduce the risk of passing infection to her newborn. (See Chapter 18 for more about HIV and AIDS.)
Diet. Good nutrition is essential to a healthy pregnancy. Nutritional counseling can help a woman create a plan for healthful eating before and during pregnancy. Diet is especially important for any woman with special nutritional needs or an eating disorder, or who is overweight or obese. Physicians commonly prescribe prenatal vitamin supplements to pregnant women. A woman of childbearing age needs extra folic acid to prevent neural tube defects in any future children she may have. Folic acid is part of a prenatal vitamin but can also be found in fortified foods such as enriched breakfast cereals, breads, and pastas. (See Chapter 12 for more information about nutrition.)
Multiple births. If twins or multiple births run in a woman's family, she is more likely to have multiple births, too. Multiple births are also more prevalent in mothers who are obese, over age 40, of African descent, or using certain reproductive technologies (such as in vitro fertilization) to become pregnant.
Genetic disorders. If either partner has a family history of any genetic disorders, genetic counseling may be in order before pregnancy. Genetic testing can determine whether the mother or father is a carrier for a specific disease. With counseling, a couple can decide how best to deal with the possibility of transferring a disease to a child. Members of some ethnic groups are at higher risk for genetic disorders. For more information about such disorders, see the box "Ethnicity and Genetic Disease."
DIVERSITY MATTERS: Ethnicity and Genetic Disease

Genes carry the biochemical instructions that determine the development of hundreds of individual traits, including disease risks, in every human being. Many conditions, such as obesity or asthma, involve multiple genes and environmental influences. Some uncommon diseases, such as sickle-cell disease or cystic fibrosis, can be traced to a mutation in a single gene.

Children inherit one set of genes from each parent. If only one copy of an abnormal gene is necessary to produce a disease, it is called a dominant gene. Diseases caused by dominant genes seldom skip a generation; anyone who carries the gene will probably be affected by the disease.

If two copies of an abnormal gene (one from each parent) are necessary for a disease to occur, the gene is called recessive. Many diseases caused by recessive genes occur disproportionately in certain racial or ethnic groups where gene pools are smaller. Prospective parents who come from the same group can be tested for recessive diseases that are known to occur in that group. If both parents are carriers, each of their children will have about a 25% chance of developing the disease.

The following list describes a few common conditions with proven genetic links in certain populations. If your family history includes of any of these conditions and you plan to have children, genetic tests and counseling can help assess the risk to your prospective children.

Sickle-cell disease occurs in about 1 of every 500 African American births and in 1 of every 36,000 Hispanic American births, according to the Centers for Disease Control and Prevention (CDC). In this disease, red blood cells, which carry oxygen to the body's tissues, change shape under conditions of stress; the normally disc-shaped cells become sickle-shaped. The altered cells carry less oxygen and can block small blood vessels. The resulting painful condition is called sickle-cell crisis. People who inherit one gene for sickle-cell disease (about 1 in 12 African Americans) experience only mild symptoms; those with two genes become severely, often fatally, ill.
Exhaustion, minor infections, and oxygen deprivation may all precipitate sickle-cell crisis. If you are at risk for sickle-cell disease, you should also have regular checkups and appropriate treatment, if required.

Hemochromatosis ("iron overload") affects about 1 in 200 people. At highest risk are people of Northern European (especially Irish), Mediterranean, and Hispanic descent. In hemochromatosis, the body absorbs and stores up to 10 times the normal amount of iron. Iron deposits form in the joints, liver, heart, and pancreas. If untreated, the disease can cause organ failure and death.
Early symptoms are often vague and include weakness, lethargy, darkening of the skin, and joint pain. Early detection and treatment are necessary to prevent damage. Treatment involves reducing iron stores by removing blood from the body (a process known as phlebotomy or "bloodletting").

Tay-Sachs disease, another recessive disorder, occurs in about 1 in 3000 Jews of Eastern European ancestry (Ashkenazi Jews), as well as those of French-Canadian and Cajun ancestry. People with Tay-Sachs disease cannot properly metabolize fatty acids. As a result, the brain and other nerve tissues deteriorate, often in childhood. Affected children show weakness in their movements and eventually develop blindness (by age 12-18 months) and seizures. This disease is fatal, and death usually occurs by age 6. No effective treatment is currently available.
Cystic fibrosis affects 1 in 3000 Caucasians; about 1 in 28 carry one copy of the cystic fibrosis gene. In cystic fibrosis, essential pancreatic enzymes are deficient, which means the body cannot properly absorb nutrients. Thick mucus impairs functioning in the lungs and intestinal tracts of people with this disease. Cystic fibrosis is often fatal in early childhood, but treatments are increasingly effective in reducing symptoms and prolonging life. In some cases, symptoms do not appear until early adulthood. In 2014, the median survival improved to 39 years from a median in the 1990s of 29.4 years due to a number of medical advances, which may include lung transplantation and inhaled antibiotics.
Thalassemia is a blood disease found most often among Italians, Greeks, and to a lesser extent, African Americans and Asians. When inherited from one parent, this form of anemia is mild; when two genes are present, the disease is severe and can cause fetal death.
Children with this condition require repeated blood transfusions, eventually resulting in a damaging iron buildup and the need for treatments that bind and remove excess iron. In severe cases, stem cell transplants from the bone marrow of a compatible sibling have shown promise with over 3000 treated individuals as of 2014. If thalassemia is treated early and aggressively, disease-free survival can approach 90%. However, not all affected individuals have an eligible donor. New interventions—such as genetic engineering, in utero stem cell transplantation, and umbilical cord blood donors—offer promise.

If you are at risk of carrying thalassemia, you should get regular checkups, monitor your health for symptoms, and learn ways to manage symptoms if they start to occur.

Canavan disease, or aspartoacylase deficiency, was first identified in the early 1900s. It causes a spongy degeneration of myelin nerve fibers in infancy and affects as many as 1 in 6400 Ashkenazi Jews. The condition presents by approximately 3 months of age and causes loss of muscle tone, which progresses to spasticity and seizures. Several treatments are under investigation, but most cases are treated with supportive care. Children with Canavan disease usually do not live beyond age 10.
Familial dysautonomia, a progressive sensorimotor neuropathy, is seen in 1 in 3700 Ashkenazi Jews. Clinically, infants show signs of decreased muscle tone and poor feeding with development of chronic lung disease and reflux. Those affected further develop hypertension. Treatment involves supportive and symptomatic therapies.
Fanconi's anemia, Type C is characterized by congenital anomalies, progressive bone marrow failure, and increased risk for certain cancers. The condition affects 1 in 100,000 people but is most common in the Ashkenazi Jewish population, in which 1 in 90 are carriers. Treatment involves hormone therapy, blood transfusion, and ultimately, stem cell transplantation. With therapy, the median survival time is to 20-30 years of age. Patients remain at high risk for infection, hemorrhage, transplant rejection, or malignancy.
Additional evaluation may be recommended for prospective parents who have recently traveled outside the United States; work with chemicals, radiation, or toxic substances; participate in physically demanding or hazardous activities or occupations; or face significant psychosocial risks, including homelessness, an unsafe home environment, or mental illness.
UNDERSTANDING FERTILITY AND INFERTILITY
Conception is a complex process. Although many couples conceive easily, others face a variety of difficulties.

Conception

The process of conception begins with the union of the nucleus of a woman's egg cell (ovum) and the nucleus of a man's sperm cell—a process called fertilization (Figure 8.1). Page 188Every month during a woman's fertile years, her body prepares itself for conception and pregnancy. In one of her ovaries, an egg matures and is released from its follicle. The egg, about the size of a fine grain of sand, travels through an oviduct, or fallopian tube, to the uterus in three to four days. The endometrium, which is the lining of the uterus, has already thickened for the implantation of a fertilized egg, that is, a zygote. If the egg is not fertilized, it lasts about 24 hours and then disintegrates. The woman's body then sheds the uterine lining during menstruation.

Diagram provides a timeline of fertilization and development of the embryo as it travels through the fallopian tube to the uterus. [D]
FIGURE 8.1 Fertilization and early development of the embryo.
Ask Yourself

QUESTIONS FOR CRITICAL THINKING AND REFLECTION
If you don't have children now, do you plan to have them someday? Have you thought about the skills and qualities that make a good parent? Given what you know about yourself today, do you think you would be a good parent? What skills or qualities do you think you would need to develop?
Fertilization

Sperm cells are produced in the man's testes and ejaculated from his penis into the woman's vagina during sexual intercourse (except in cases of artificial insemination or assisted reproduction; see the section "Treating Infertility"). Sperm cells are much smaller than eggs. The typical ejaculate contains millions of sperm, but only a few complete the journey through the uterus and up the fallopian tube to the egg. Many sperm cells do not survive the vagina's acidic environment.

Once through the cervix and into the uterus, many sperm cells are diverted to the wrong oviduct or get stuck along the way. Of those that reach the egg, only one will penetrate its hard outer layer. As sperm approach the egg, they release enzymes that soften this outer layer. Enzymes from hundreds of sperm must be released in order for the egg's outer layer to soften enough to allow one sperm cell to penetrate. The first sperm cell that bumps into a spot that is soft enough can swim into the egg cell. It then fuses with the nucleus of the egg, and fertilization occurs. The sperm's tail, its means of locomotion, is left behind on the egg's outer membrane, while the sperm's head is inside the egg. The egg then undergoes chemical change that makes it impenetrable to other sperm.

The ovum carries the hereditary characteristics of the mother and her ancestors; sperm cells carry the hereditary characteristics of the father and his ancestors. Each parent cell—egg or sperm—contains 23 chromosomes, each of which contains genes, which are packages of biochemical instructions for the developing baby. Genes provide the blueprint for a unique individual based on the functional and health characteristics of his or her ancestors (see the box "Creating a Family Health Tree").

ASSESS YOURSELF: Creating a Family Health Tree

Although 99% of our genes are identical to that of our peers, it is the 1% that makes up the differences in our hair and eye color, and also makes us susceptible to developing certain diseases and disorders. We inherit these differences from our parents—and pass them on to our children. In fact, heredity is the primary cause for uncommon illnesses such as hemophilia and sickle-cell disease. You will get these illnesses if your parents pass on the necessary genes. Researchers have found a genetic influence in many common disorders, including obesity and heart disease as well as diabetes, depression, asthma, alcohol and drug abuse, and certain forms of cancer. In fact, the single most reliable indicator for future alcohol or drug abuse is family history.

Knowing that a specific disease runs in your family allows you to seek early screening and modify behavior, which can greatly affect your long-term health. For example, an individual with a family history of high cholesterol and early heart disease can increase physical activity and pay special attention to diet.

Inherited diseases tend to show distinct patterns. In general, the more first-degree relatives you have with a genetically transmitted disease, the greater your risk. However, nongenetic factors—such as health habits—can also play a role. Signs of strong hereditary influence include early onset of a disease, appearance of the disease largely or exclusively on one side of the family, onset of the same disease at the same age in more than one relative, and development of the disease despite good health habits.

You can put together a simple family health tree by compiling a few key facts about your primary relatives: siblings, parents, aunts and uncles, and grandparents. Those facts include the dates of birth, major diseases, health-related conditions and habits, and, for deceased relatives, the ages at death as well as the causes. Because certain diseases are more common in particular ethnic groups, also record the ethnic background of each grandparent. Next create a tree, using the example as a guide. An alternate way to construct a family tree is through the Surgeon General's My Family Health Portrait Tool, accessible online. Show your tree to a physician or genetic counselor, who can help you target the health behaviors and screening tests that are most important for you and help you determine whether genetic testing might be appropriate.

A Sample Family Health Tree and What It Means
Penny is a 25-year-old woman who prepared this family tree. She has a strong family history of breast and ovarian cancer that developed early in life on her mother's side. Based on this information, her physician may suggest earlier breast screening or genetic testing for mutations in the BRCA genes to help gauge her risk of getting the disease. She also has several close relatives on her father's side of the family who were obese and suffered from high cholesterol and heart attacks at early ages. These risk factors significantly increase Penny's chance of having a heart attack. As such, Penny and her brother should modify their lifestyles early in order to avoid high cholesterol and prevent obesity later.

As the family tree shows, Penny's paternal grandmother also died of breast cancer—but at the age of 88. Because this case happened late in life, the heritable risk on the paternal side is not as likely. A paternal grandmother is also a more distant relative than a mother or sister (first-degree relative). Penny's risk of breast cancer is almost entirely limited to the maternal side of her family tree.

A family health tree can be a "living document." By examining your family's health history, you can make important decisions about lifestyle, screening, and counseling. In Penny's case, such decisions have an impact not only on herself, but also on her daughters.

sources: U.S. Department of Health & Human Services. Surgeon General's Family Health History Initiative (http://www.hhs.gov/familyhistory/); Carmona, R. H., and D. J. Wattendorf. 2005. "Personalizing prevention: The U.S. Surgeon General's Family History Initiative." American Family Physician 71(1): 36-39; Hobson, K. 2009. "Why and how to put together a family history." US News & World Report, 30 July; Preidt, R. 2014. "Only close family history needed for cancer risk assessment." US News & World Report, 4 February.

Upon fertilization, the zygote undergoes cell division and the growth process begins. The zygote continues to divide as it travels through the oviduct to the uterus. When it reaches the uterus, the cluster of 32-128 cells (now called a blastocyst) attaches to the uterine wall. Soon it becomes implanted in the endometrium and becomes an embryo.Page 190

Twins

In the usual course of events, one egg and one sperm unite to produce one fertilized egg and one baby. But if the ovaries release two eggs during ovulation and both eggs are fertilized, twins develop. These twins will be no more alike than siblings from different pregnancies because each will have come from a different fertilized egg. Twins who develop this way are referred to as fraternal (dizygotic) twins; they may be the same sex or different sexes. About 70% of twins are fraternal.

Twins can also develop from the early division of a single fertilized egg into two cells that develop separately. Because these babies share all genetic material, they will be identical (monozygotic) twins.

If two or more eggs are released and fertilized, leading to the development of two or more fetuses in the same pregnancy, this is called multiple gestation and leads to a multiple birth. The most serious complication of multiple births is preterm delivery (delivery before the fetuses are adequately mature). The higher the number of fetuses a woman carries, the earlier in gestation she will deliver. This leads to higher rates of complications due to prematurity.

Infertility

About 2 million American couples have difficulty conceiving. Infertility is defined as the inability to conceive after trying for a year or more. Infertility affected about 6.1% of American women of reproductive age (15-44 years) in the United States in 2013. Over 1 million women seek treatment for infertility each year. Although the focus is often on women, one-fourth (26%) of the factors contributing to infertility are male, and in one-third (35%) of infertile couples, both partners have problems. Therefore, it is important that both partners be evaluated.

Female Infertility

One-third of cases of female infertility usually result from one of two key causes—tubal blockage (14%) or failure to ovulate (21%). An additional one-third (37%) of cases of female infertility are due to anatomical abnormalities, benign growths in the uterus, thyroid disease, and other uncommon conditions; the remaining 28% of cases are unexplained.

Blocked oviducts are most commonly the result of pelvic inflammatory disease (PID), a serious complication of several STIs. One study found that of 100,000 women aged 20-24 who were diagnosed with PID, 16,800 (one of every six) went on to have problems with infertility. Most cases of PID are associated with untreated cases of chlamydia or gonorrhea, both of which can occur without symptoms. As of 2014, the CDC estimates that more than 2.86 million cases of gonorrhea and chlamydia occur each year. Tubal blockages can also be caused by prior surgery or by endometriosis, a condition in which endometrial (uterine) tissue grows outside the uterus. This tissue responds to hormones and can cause pelvic pain, bleeding, scarring, and adhesions (scar tissue). Endometriosis is typically treated with hormonal therapy and surgery.

Age also affects fertility. Beginning at around age 30, a woman's fertility naturally begins to wane. Age is probably the main factor in ovulation failure. Exposure to toxic chemicals, cigarette smoke, or radiation also appears to reduce fertility, as do genetic factors identifiable in your family history (see the box "Creating a Family Health Tree").

Male Infertility

Male infertility accounts for about one-fourth (26%) of infertile couples. The leading causes of male infertility can be divided into four main categories: hypothalamic pituitary disease (1-2%), testicular disease (30-40%), disorders of sperm transport or posttesticular disorders (10-20%), and unexplained (40-50%). Some acquired disorders of the testes can lead to infertility, such as damage from the following causes:

Drug use (large doses of marijuana, for example, cause lower sperm counts and suppress reproductive hormones)
Radiation
Infection, such as from having had mumps as a child
Environmental toxins
Hyperthermia, such as from prolonged hot tub use
Smoking
Treating Infertility

The cause of infertility can be determined for about 72-85% of infertile couples. Most cases of infertility are treated with conventional medical therapies. Surgery can repair oviducts, remove endometriosis, and correct anatomical problems in men and women. Fertility drugs can help women ovulate but may cause multiple births. If these conventional treatments don't work, couples can turn to assisted reproductive technology (ART) techniques, as described in the following sections. According to 2016 estimates from the CDC, about 1.6% of births in the United States are the result of ART treatments.

Most infertility treatments are expensive and emotionally draining, with a live birth occurring in about a third of cases. Some infertile couples choose not to try to have children, whereas others turn to adoption. One measure you can take to avoid infertility is to follow the CDC recommendation of STI screening every year for all sexually active women younger than 25 years. Couples will need to balance the risks of age-related infertility with the competing demands of careers and academics.Page 191

Intrauterine Insemination

Male infertility can sometimes be overcome by collecting and concentrating the man's sperm and introducing the semen by syringe into a woman's vagina or uterus, a procedure known as artificial (intrauterine) insemination. To increase the probability of success, the woman is often given fertility drugs to induce ovulation prior to the insemination procedure. The sperm can be provided by the woman's partner or a donor. Donor sperm are also used by single women and lesbian couples who want to conceive using artificial insemination. The success rate is about 5-20%. The wide range is due to age-related influences.

QUICK STATS

More than 200,000 ART procedures were performed in the United States in 2014, resulting in more than 70,000 babies.

—Centers for Disease Control and Prevention, 2016
IVF

A surgical technique used to overcome infertility, in vitro fertilization (IVF) involves surgically removing mature eggs from a woman's ovary and pairing the harvested eggs with sperm outside the woman's body (in vitro), in a laboratory dish. If eggs are successfully fertilized, one or more of the resulting embryos are inserted into the woman's uterus. The remaining embryos can then be frozen for future use.

There are disadvantages to IVF. Success rates determined by live birth rates vary from about 4% to 40% depending on the woman's age. It costs more than $10,000 per procedure and may require five or more attempts to produce one live birth. IVF also increases the chance of twins or triplets, which in turn increases the risk of premature birth and maternal complications, including pregnancy-related hypertension and diabetes.

Gestational Carrier

A gestational carrier is a fertile woman who agrees to carry a fetus for an infertile couple. The gestational carrier agrees to be artificially inseminated by the father's sperm or to undergo IVF with the couple's embryo, to carry the baby to term, and to give it to the couple at birth. In return, the couple pays her for her services and medical costs (typically around $50,000). As of 2013, less than 1% of all ART in the United States is performed through gestational carriers.

Emotional Responses to Infertility

Couples who seek treatment for infertility have often already confronted the possibility of not being able to become biological parents. Many infertile couples feel they have lost control over a major facet of their lives. They may lose perspective on the rest of their lives as they focus more and more on the reasons for their infertility and on treatment. Infertile couples may need to set their own limits on how much treatment they are willing to undergo.

Support groups for infertile couples can provide help in this difficult situation, but there are few easy answers to infertility. If treatment is unsuccessful, couples must mourn the loss of the children they will never bear. They need to make a decision about their future—whether to pursue alternate plans or further treatment, or to adjust to childlessness and go on with their lives.

Ask Yourself

QUESTIONS FOR CRITICAL THINKING AND REFLECTION
What are your views on infertility treatments? Do you feel treatment is appropriate, or do you think infertile couples should adopt children? If you were faced with a diagnosis of infertility, what would you consider doing?
PREGNANCY
Pregnancy is usually discussed in terms of trimesters—three periods of about three months (or 13 weeks) each. During the first trimester, the mother experiences a few physical changes and some fairly common symptoms. During the second trimester, often the most peaceful time of pregnancy, the mother gains weight, looks noticeably pregnant, and may experience a general sense of well-being if she is happy about having a child. The third trimester is the hardest for the mother because she must breathe, digest, excrete, and circulate blood for herself and the growing fetus. The weight of the fetus, the pressure of its body on her organs, and its increased demands on her system cause discomfort and fatigue and may make the mother increasingly impatient to give birth.

Changes in the Woman's Body

Hormonal changes begin as soon as an egg is fertilized, and for the next nine months the woman's body nourishes the fetus and adjusts to its growth (Figure 8.2).

Diagram summarizes pregnancy changes by organ and body system. [D]
FIGURE 8.2 Physiological changes during pregnancy.
Early Signs and Symptoms

Early recognition of pregnancy is important, especially for women with medical conditions or nutritional deficiencies. The following symptoms are not absolute indications of pregnancy, but they are reasons to visit a gynecologist, and maybe take a Page 192home pregnancy test (see the box "Home Pregnancy Tests"):

A missed menstrual period. When a fertilized egg implants in the uterine wall, the endometrium is retained to nourish the embryo. A woman who misses a period after having intercourse may be pregnant.
Slight bleeding. Following implantation of the fertilized egg into the endometrial lining, a slight bleed occurs in about 14% of pregnant women. Because this happens about when a period is expected, about two weeks after ovulation, the bleeding is sometimes mistaken for menstrual flow. It usually lasts only a few days.
Nausea. Between 50 and 90% of pregnant women feel increased nausea, probably in reaction to surging levels of progesterone and other pregnancy hormones. Although this nausea is often called morning sickness, some women have it all day long. It frequently begins during the 6th week and disappears by the 12th week. In some cases it continues throughout the pregnancy.
Breast tenderness. Some women experience breast tenderness, swelling, and tingling, usually described as different from the tenderness experienced before menstruation.
Increased urination. Increased frequency of urination can occur soon after the missed period.
Sleepiness, fatigue, and emotional upset. These symptoms result from hormonal changes. Fatigue can be surprisingly overwhelming in the first trimester but usually improves significantly around the third month of pregnancy.
CRITICAL CONSUMER: Home Pregnancy Tests

Women have access to a variety of over-the-counter home pregnancy tests today, but generally speaking, these tests all work in the same way to determine whether a woman is pregnant. Pregnancy tests are designed to detect the presence of the hormone human chorionic gonadotropin (hCG), a hormone produced by the implanted fertilized egg, which is discussed in this chapter. Because the placenta releases hCG, the hormone can be detected in a woman's urine or blood when she is pregnant.

Although home pregnancy tests have become extremely accurate since their introduction in 1975, not all tests behave equally. A sensitive test will give a "positive" result with very low levels of hCG and can identify pregnancies earlier. A less sensitive test may not give an accurate result until hCG levels are much higher. Most kits will reliably detect 97% of pregnancies one week after a missed period. In 85% of normal pregnancies, the hCG levels should double every two to three days, and many women won't have a positive test result until the first day of a missed period or even a few days later.

Two types of home pregnancy tests are available—those that require the test strip to be dipped into urine, and those that require the user to urinate directly onto the test strip. Different tests use different mechanisms to display test results. Some use symbols such as a + or − sign, some spell out the words "pregnant" and "not pregnant," and others utilize a color scheme.

A clinical blood test is more accurate but not necessarily more sensitive than a home pregnancy test. A quantitative blood test, usually called a beta hCG test, measures the exact number of units of hCG in the blood. This type of test can detect even the most minimal level. Labs vary in what is considered a positive pregnancy test. Common cutoffs for positive are 5, 10, and 25 units. A level under 5 is considered negative.

Women need to use home pregnancy test kits with a clear understanding of their limitations. If you're comfortable waiting, a sensitive test taken a week after your period is due will almost certainly give you accurate results. If you elect to take the test as early as the day after you've missed your period, remember that a negative result isn't 100% certain. A positive result may mean either a viable pregnancy or a pregnancy destined to end shortly after it began. With either of those results, you should plan to test again a week later, just to be sure. For that reason, it's a good idea to buy tests in pairs; 15 of the 18 commercially available home testing products come as multiple-test kits.
The first reliable physical signs of pregnancy can be distinguished about four weeks after a woman misses her menstrual period. Increased uterine growth and blood flow contribute to softening of the uterus just above the cervix, called Hegar's sign, and a bluish discoloration to the cervix and labia minora, termed Chadwick's sign.

Four weeks after a woman misses her menstrual period, she is considered to be about eight weeks pregnant because pregnancy is calculated from the time of a woman's last menstrual period rather than from the time of fertilization. The uterine lining buildup in those two weeks before fertilization is part of the gestation cycle, and the timing of ovulation and fertilization is often difficult to determine. Although a woman should see her physician to determine her due date, due dates can be approximated by subtracting three months from the date of the last menstrual period and then adding Page 193seven days. For example, a woman whose last menstrual period began on September 20 would have a due date of about June 27.

Continuing Changes in the Woman's Body

The most obvious changes during pregnancy occur in the reproductive organs. During the first three months, the uterus enlarges to about three times its nonpregnant size, but it still cannot be felt in the abdomen. By the fourth month, it is large enough to make the abdomen protrude. By the seventh or eighth month, the uterus pushes up under the rib cage, which makes breathing slightly more difficult. The breasts enlarge and are sensitive; by week 8, they may tingle or throb. The pigmented area around the nipple, called the areola, darkens and broadens. The hormones of pregnancy also contribute to hyperpigmentation and broadening of the nipple, and for some women, hyperpigmentation may show in the face or the midline of the abdomen.

Other changes are going on as well. Early in pregnancy, the muscles and ligaments attached to bones begin to soften and stretch. The joints between the pelvic bones loosen and spread, making it easier to have a baby but harder to walk. The circulatory system becomes more efficient to accommodate higher blood volume, which increases by 50%, and the heart pumps more rapidly. Much of the increased blood flow goes to the uterus and placenta (the organ that exchanges nutrients and waste between mother and fetus). The mother's lungs also become more efficient, and her rib cage widens to permit her to inhale up to 40% more air. Much of the oxygen goes to the fetus. The kidneys become highly efficient, removing waste products from fetal circulation and producing large amounts of urine by midpregnancy.

The average weight gain during a healthy pregnancy is 27.5 pounds, although actual weight change varies with the individual. Table 8.1 shows the weight gains recommended by the Institute of Medicine based on a woman's prepregnancy weight status. About half of the weight gain is directly related to the baby (such as the fetus and placenta); the rest accumulates over the woman's body as fluid and fat. As the woman's skin stretches, small breaks may occur in the elastin fibers of the lower layer of skin, producing stretch marks on her abdomen, hips, breasts, or thighs.

Table 8.1 Recommended Weight Gain during Pregnancy
STATUS (BMI)*
WEIGHT GAIN (POUNDS)
Underweight (<18.5)
28-40
Normal (18.5-24.9)
25-35
Overweight (25-29.9)
15-25
Obese (>30)
11-20
*BMI, or body mass index, allows comparison of body weight across different heights. (See Chapter 14 to calculate BMI.)
Changes during the Later Stages of Pregnancy

By the end of the sixth month, the increased needs of the fetus place a burden on the mother's lungs, heart, and kidneys. Her back may ache from the pressure of the baby's weight and from having to throw her shoulders back to keep her balance while standing (Figure 8.3). Her body retains more water, perhaps up to three extra quarts of fluid. Her hands, legs, ankles, or feet may swell, and she may be bothered by leg cramps, heartburn, or constipation. Despite discomfort, both her digestion and her metabolism are working at top efficiency.

An internal view shows the mother's lungs, stomach, liver, kidney, colon, and bladder are cramped due to the size of the fetus.
FIGURE 8.3 The fetus during the third trimester of pregnancy.
Near term, the uterus prepares for childbirth with a series of preliminary contractions, called Braxton Hicks contractions. Unlike true labor contractions, Braxton Hicks contractions are irregular with short duration; they are also often painless. To the mother, a contraction may initially feel only as though her abdomen is hard to the touch. As the delivery date approaches, true labor contractions become more frequent, regular, and intense, ultimately resulting in labor.Page 194

In the ninth month, increased joint laxity coupled by a softening cervix allows the baby to settle deeper into the pelvis. This process, called lightening, produces a visible change in the mother's abdominal profile. Pelvic pressure increases, and pressure on the diaphragm lightens. Breathing becomes easier; urination becomes more frequent. Sometimes, after a first pregnancy, lightening does not occur until labor begins.

QUICK STATS

Up to 23% of women have symptoms of depression during pregnancy.

—American Pregnancy Association
Emotional Responses to Pregnancy

Rapid changes in hormone levels can cause a pregnant woman to experience unpredictable emotions. A large part of pregnancy is beyond the woman's control—her changing appearance, her energy level, her variable moods—and some women need extra support and reassurance to stay on an even keel. Hormonal changes can also make women feel exhilarated and euphoric, although for some women such moods are temporary.

Like the physical changes that accompany pregnancy, emotional responses also change as the pregnancy develops. During the first trimester, the pregnant woman may fear that she may miscarry or that the child will not be normal. Education about pregnancy and childbirth and support from her partner, friends, relatives, and health care professionals are important antidotes to these fears.

During the second trimester, the pregnant woman can feel early fetal movements, and worries about miscarriages usually begin to diminish. She may look and feel happy and be delighted as her pregnancy begins to show. However, she may also worry that her increasing size makes her unattractive. Reassurance from her partner, family, and other support systems can ease these fears.

The third trimester is the time of greatest physical stress during the pregnancy. A woman may find that her physical abilities are limited by her size. Because some women feel physically awkward and sexually unattractive, they may experience periods of depression. But many also feel a great deal of happy excitement and anticipation. The fetus may already be looked on as a member of the family, and both parents may begin talking to the fetus and interacting with it by patting the mother's belly. The upcoming birth will probably be a focus for both the woman and her partner.
FETAL DEVELOPMENT
Now that we've seen what happens to the mother's body during pregnancy, let's consider the development of the fetus (Figure 8.4).

Diagram summarized prenatal milestones by week from last menstrual period to typical full-term birth. [D]
FIGURE 8.4 A chronology of milestones in prenatal development.
The First Trimester

About 30 hours after an egg is first fertilized, the cell divides, and this process of cell division repeats many times. As the cluster of cells drifts along the oviduct, several different kinds of cells emerge. The entire set of genetic instructions is passed to every cell, but each cell follows only a specific subset of the instructions; if this were not the case, there would be no different organs or body parts. For example, all cells carry genes for hair color and eye color, but only the cells of the hair follicles and irises (of the eye) respond to that information. This process of individual cells developing into specific organs and structures is called differentiation.

On about the fourth day after fertilization, the cluster of rapidly developing cells arrives in the uterus as a blastocyst, or a mostly hollow sphere of between 32 and 128 cells. The blastocyst attaches to the uterine wall on the sixth or seventh day, allowing for implantation into the nourishing uterine lining.

The blastocyst becomes an embryo by about the end of the second week after fertilization. The inner cells of the Page 195blastocyst separate into three layers. One layer becomes inner body parts—the digestive and respiratory systems; the middle layer becomes muscle, bone, blood, kidneys, and sex glands; and the third layer becomes the skin, hair, and nervous tissue.

The outermost shell of cells becomes the supporting structures of the pregnancy: the placenta, umbilical cord, and amniotic sac (Figure 8.5). A network of blood vessels called chorionic villi eventually forms the placenta. The human placenta allows a two-way exchange of nutrients and waste materials between the mother and the fetus. The placenta brings oxygen and nutrients to the fetus and transports waste products out. The placenta does not provide a perfect barrier between the fetal circulation and the maternal circulation, however. Some blood cells are exchanged, and certain substances, such as alcohol, pass freely from the maternal circulation through the placenta to the fetus.


FIGURE 8.5 A cross-sectional view of the fetus in the uterus and an enlargement of the placenta.
The period between weeks 2 and 9 is a time of rapid differentiation and change. All major body structures are formed during this time, including the heart, brain, liver, lungs, and sex organs. Eyes, nose, ears, arms, and legs also appear. Some organs begin to function, as well; the heart begins to beat, and the liver starts producing blood cells. Because body structures are forming, the developing organism is vulnerable to damage from environmental influences such as drugs and infections (discussed in detail in sections that follow).

By the end of the second month, the fetal brain sends out impulses that coordinate the functioning of its other organs. The embryo is now a fetus, and further changes will be in the size and refinement of working body parts. In the third month, the fetus becomes active. By the end of the first trimester, at 13 weeks, the fetus is about an inch long and weighs less than one ounce.

The Second Trimester

To grow during the second trimester, to about 14 inches and 1.5 pounds, the fetus requires large amounts of food, oxygen, and water, which come from the mother through the placenta. All body systems are operating, and the fetal heartbeat can be heard with a stethoscope. By the fourth or fifth month, the mother can detect early fetal movements that may feel like Page 196"flutters." A fetus born at 24-26 weeks has a better than 50% chance of survival. The age at which survival is possible depends on the development of lung tissue, which completes a critical step in weeks 24-26 of pregnancy. Prior to 23 weeks, survival without significant impairment is rare, occurring in 3-15% of cases.

The Third Trimester

The fetus gains most of its birth weight during the last three months of the pregnancy. Some of the weight is brown fat under the skin that insulates the fetus and supplies food. Brown fat is a special fat rich with blood supply found in hibernating mammals and newborns and is associated with protection against hypothermia. This is an important consideration because babies are often too small to generate much of their own heat and are too weak to move away from cold areas. The fetus also takes in other nutrients; about 85% of the calcium and iron the mother consumes goes into the fetal bloodstream.

The fetus may live if it is born during the seventh month, but it needs the fat layer acquired in the eighth month and time for organs—especially the respiratory and digestive organs—to develop. It also needs the immunity supplied by antibodies in the mother's blood during the final three months. The antibodies protect the fetus against many of the diseases to which the mother has acquired immunity.

Diagnosing Fetal Abnormalities

About 3% of babies are born with a major birth defect. Information about the health and sex of a fetus can be obtained prior to birth through prenatal testing.


At the beginning of the third trimester, the fetus is growing rapidly, weighs about 2½ pounds, and measures about the size of a cantaloupe. The fetus is typically active and can suck its thumb, blink, frown, and turn its head.
© Tissuepix/Photo Researchers, Inc.
Page 197
Noninvasive Screening Tests

Maternal blood testing can be used to help identify fetuses with neural tube defects, Down syndrome, and other anomalies. Traditionally, blood is taken from the mother at 16-19 weeks of pregnancy and analyzed for four hormone levels—human chorionic gonadotropin (hCG), unconjugated estriol, alpha-fetoprotein (AFP), and inhibin-A. These four hormones levels, the quadruple marker screen (QMS), can be compared to appropriate standards, and the results are used to estimate the probability that the fetus has particular anomalies. This type of test is a screening test rather than a diagnostic test; in the case of abnormal QMS results, parents may choose further testing such as an amniocentesis or ultrasonography.

A newer noninvasive screening test, cell-free DNA, uses small fragments of fetal DNA identified in the maternal serum typically after 10 weeks of pregnancy. Currently, this DNA is used primarily to identify chromosomal disorders, such as Down syndrome, in women with elevated risk for aneuploidy (an abnormal number of chromosomes in the fetus) such as pregnant women over age 35, or in cases where the fetus is known to be at risk for a particular chromosomal or genetic defect. With time and further research, this tool has tremendous potential to revolutionize prenatal testing for rare inherited conditions.

Invasive Diagnostic Tests

Chorionic villus sampling (CVS) is a diagnostic test that can be performed in weeks 10 through 12 of pregnancy for high-risk women or women with abnormal screening results. This procedure involves removing a tiny section of the chorionic villi, which contain fetal cells that can be analyzed. For later diagnosis, amniocentesis is typically performed between 16 and 22 weeks and removes fluid from around the developing fetus. The fluid contains fetal skin cells that can be cultured for analysis. This analysis can include genetic analyses for chromosomal disorders but also for some genetic diseases, like Tay-Sachs disease. Because the genetics are known, the sex of the fetus can also be determined. Invasive testing carries a slight risk (a 0.1-0.7% chance of miscarriage).

Ultrasonography

Ultrasonography (also called ultrasound) uses high-frequency sound waves to create a sonogram, or visual image, of the fetus in the uterus. Sonograms show the fetus's position, size, and gestational age, and identify the presence of certain anatomical problems. Sonograms can sometimes be used to determine the sex of the fetus. Sonograms are considered safe for a pregnant woman and the fetus, but the U.S. Food and Drug Administration (FDA) advises against "keepsake" sonograms performed for no medical purpose.

First-trimester screening for Down syndrome combines ultrasound evaluation of nuchal translucency (the thickness of the back of the fetus's neck) with maternal blood testing. This test can be done between the 10th and 14th weeks of pregnancy. This can be combined with serum testing at 16 weeks for a sequential screen to improve the sensitivity of noninvasive screening tests. If results indicate an increased risk of abnormality, further diagnostic studies such as amniocentesis can be done for confirmation.

Genetic Counseling

Genetic counselors explain the results of the various tests so that parents can understand their implications. If a fetus is found to have a defect, it may be carried to term, aborted, or in rare instances, receive treatment while still in the uterus. Results of most current screening tests are not available until after week 12 of pregnancy; consequently, if abortion is chosen, it is likely to involve one of the more medically complex and physically difficult methods (see Chapter 7).

Fetal Programming

Prenatal testing techniques look for chromosomal, genetic, and other anomalies that typically cause immediate problems. A new area of study known as fetal programming theory focuses on how conditions in the womb may influence the risk of adult diseases. For example, researchers have linked low birth weight to an increased risk of heart disease, high blood pressure, obesity, diabetes, and schizophrenia. High birth weight in female infants, however, has been linked to an increased risk of hypertension, diabetes, and some cancers in later life.

How might conditions during gestation affect the risk of adult diseases? A number of studies have looked at groups of people born in areas of poverty or at times of famine, when pregnant women were unable to eat properly. The poor prenatal conditions that stunt the growth of a developing fetus and lead to low birth weight may also affect specific organs. For example, if energy is limited, resources may be directed toward the developing fetal brain and away from other organs, including the liver and kidneys. Later in life, a small liver may be unable to clear cholesterol from the bloodstream, thereby increasing cholesterol levels and raising the risk of heart disease; undersized kidneys may be less able to regulate blood pressure. The fetus may also respond to limited resources by developing a permanently thrifty metabolism that triggers increased appetite and fat storage—leading to a greater risk of adult obesity and diabetes. Stress, both physical and emotional, increases maternal levels of the Page 198hormone cortisol, which in turn may permanently affect an infant's system of blood pressure regulation.


Ultrasonography provides information about the position, size, and physical condition of a fetus in the uterus.
© Monkey Business Images/Shutterstock
Hormones may also be involved in the link between high birth weight and increased risk of breast cancer. Hormones that contribute to high birth weight include leptin, insulin, and estrogen. Exposure to high levels of these in the womb may alter developing breast tissue in such a way that, when exposed to estrogen later in life, breast cells may be more likely to become malignant.

Although not all scientists embrace fetal programming theory, these studies emphasize that everything that occurs during pregnancy can have an impact on the developing fetus. In the future, people may be able to use information about their birth weight and other indicators of gestational conditions just as they now can use family history and genetic information—to alert them to special health risks and to help them improve their health.
THE IMPORTANCE OF PRENATAL CARE
Adequate prenatal care—as described in the following sections—is essential to the health of both mother and baby. All physicians recommend that women start getting regular prenatal checkups as soon as they become pregnant. Typically this means one checkup per month during the first eight months and then one checkup per week during the final month. About 84% of pregnant women begin receiving adequate prenatal care during the first trimester; about 3.5% wait until the last trimester or receive no prenatal care at all.

Regular Checkups

In the woman's first visit to her obstetrician, she will be asked for a detailed medical history of herself and her family. Her obstetrician will note any hereditary conditions that may assume increased significance during pregnancy. The tendency to develop gestational diabetes (diabetes during pregnancy only), for example, can be inherited; appropriate treatment during pregnancy reduces the risk of serious harm.

The woman is given a complete physical exam and is informed about appropriate diet. She returns for regular checkups throughout the pregnancy, during which her blood pressure and weight gain are measured, her urine is analyzed, and the fetus's size and position are monitored. Regular prenatal visits give the mother a chance to discuss her concerns and be assured that everything is proceeding normally. Physicians, midwives, health educators, and teachers of childbirth classes can provide the mother with valuable information.

Blood Tests

A blood sample is taken during the initial prenatal visit to determine blood type and detect possible anemia or Rh incompatibilities. The Rh factor is a blood protein. If an Rh-positive father and an Rh-negative mother conceive an Rh-positive baby, the baby's blood will be incompatible with the mother's blood. If some of the baby's blood enters the mother's bloodstream during delivery, she will develop anti-Rh antibodies just as she would toward a virus. If she has subsequent Rh-positive babies, the circulating antibodies in the mother's blood, passing through the placenta, will destroy the fetus's red blood cells, possibly leading to jaundice, anemia, or death. This condition is completely preventable with a serum called Rh-immune globulin, which coats Rh-positive cells as they enter the mother's body and prevents her immune system from recognizing them and forming antibodies. Rh-immune globulin is given to Rh-negative mothers in the third trimester and again after the birth if the baby is found to be Rh-positive.

Blood may also be tested for evidence of hepatitis B, syphilis, rubella immunity, thyroid problems, and, with the mother's permission, HIV infection.

Prenatal Nutrition

A nutritious diet throughout pregnancy is essential for both the mother and her unborn baby. Not only does the baby get all its nutrients from the mother, but it also competes with her for nutrients not sufficiently available to meet both their needs. When a woman's diet is low in iron or calcium, the fetus receives most of it, and the mother may become deficient in Page 199the mineral. To meet the increased nutritional demands of her body, a pregnant woman shouldn't just eat more; she should make sure that her diet is nutritionally adequate.

To maintain her own health and help the fetus grow, a pregnant woman typically needs to consume about 250-500 extra calories per day. Breastfeeding an infant requires even more energy—about 500 or more calories per day. To ensure that she's getting enough calories and nutrients, a pregnant woman should talk to her physician or a registered dietician about her dietary habits and determine what changes she should make.

Some physicians prescribe high-potency vitamin and mineral supplements to pregnant and lactating women. Supplements can help boost the levels of nutrients available to mother and child, helping with fetal development while ensuring that the mother doesn't become nutrient-deficient. Pregnant and lactating women, however, should not take supplements without the advice of their physicians because some vitamins, such as vitamin A, can be harmful if taken in excess. Pregnant women also should not take herbal dietary supplements without consulting a physician.

Two vitamins—vitamin D and the B vitamin folate—are particularly important to pregnant women. Pregnant women who do not get enough vitamin D are more likely to deliver low-birth-weight babies. Chronic vitamin D deficiency has been linked to other health problems, including heart disease.

If a woman does not get the recommended daily amount of folate, both before and during pregnancy, her child has an increased risk of neural tube defects, including spina bifida. Any woman capable of becoming pregnant should get at least 400 micrograms (0.4 milligrams) of folic acid (the synthetic form of folate) daily from fortified foods and/or supplements, in addition to folate from a varied diet. Pregnant women should get 1000 micrograms (1 milligram) every day.

Food safety is another special dietary concern for pregnant women because foodborne pathogens can be especially dangerous to them and their unborn children. Germs and parasites such as Listeria monocytogenes and Toxoplasma gondii are both particularly worrisome. To avoid them, pregnant women should avoid eating undercooked and ready-to-eat meats (such as hot dogs and pre-packaged deli meats) and should wash produce thoroughly before eating it. Pregnant women should also follow the FDA's recommendations for consumption of fish and seafood. For complete information about nutrition and food safety, see Chapter 12.

Avoiding Drugs and Other Environmental Hazards

Everything the mother ingests may eventually reach the fetus in some proportion. In addition to the food the mother eats, the drugs she takes and the chemicals she is exposed to affect the fetus. Some drugs harm the fetus but not the mother because the fetus is in the process of developing and because the proper dose for the mother is a proportionately massive dose for the fetus.


A woman's dietary needs change during pregnancy, so it's important to eat a nutritionally sound diet.
© Tim Platt/Getty Images
During the first trimester, when the major body structures are forming rapidly, the fetus is extremely vulnerable to environmental factors such as viral infections, radiation, drugs, and other teratogens, any of which can cause congenital malformations, or birth defects. As most organs are developing during the first trimester, exposures are of special concern during this critical window. The rubella (German measles) virus, for example, can cause congenital malformation of nerves supplying the eyes and ears in the first trimester, leading to blindness or deafness, but exposure to it later in the pregnancy does no damage. Similarly, excess retinoic acid (Vitamin A) exposure in the first trimester can lead to spontaneous abortion and fetal malformations such as microcephaly and cardiac anomalies. Another example is the class of medications known as anti-epileptics (such as valproic acid), which is associated with cleft palate and neural tube defect. The most common congenital malformations identified are Page 200open neural tube, cardiac defects, urinary tract defects, skeletal abnormalities, and cleft palates. Women who are taking medications known to cause birth defects must take care to avoid pregnancy (see Chapter 6 on contraception).

Alcohol

Alcohol is a potent teratogen. Although 1 in 10 pregnant women reports an alcohol exposure at some point, getting drunk just one time during pregnancy may be enough to cause damage in a fetus. A high level of alcohol consumption during pregnancy is associated with spontaneous miscarriage and stillbirth. Fetuses born to mothers who have consumed alcohol are at risk for fetal alcohol syndrome (FAS). A baby born with FAS is likely to be characterized by mental impairment, a small head and body size, unusual facial features, congenital heart defects, defective joints, impaired vision, and abnormal behavior patterns. Researchers doubt that any level of alcohol consumption is safe, and they recommend total abstinence during pregnancy (see Chapter 10).

Tobacco

About 10% of all women smoke during pregnancy. Pregnant women who smoke should be counseled to quit, and nonsmoking pregnant women should avoid places where people smoke. Smoking is a preventable risk factor associated with miscarriage, low birth weight, preterm birth, infant death, and other pregnancy complications that may occur via direct damage to genetic material. Nicotine, the active ingredient in cigarette smoke, impairs oxygen delivery to the fetus and leads to faster fetal heart rates and reduced fetal breathing.

Babies born to women who smoke during pregnancy have poorer lung function at birth. After delivery, exposure to second-hand smoke increases the infant's susceptibility to pneumonia, bronchitis, and sudden infant death syndrome (SIDS). Up to 34% of SIDS cases have been attributed to tobacco use. If a mother who smokes breastfeeds, her infant will be exposed to tobacco chemicals through breast milk. See Chapter 11 for more about the effects of smoking.

QUICK STATS

About 1% of school-aged children in the United States have symptoms of fetal alcohol syndrome.

—Centers for Disease Control and Prevention, 2015
Caffeine

Caffeine, a powerful stimulant, puts both mother and fetus under stress by raising the level of the hormone epinephrine. Caffeine also reduces the blood supply to the uterus. One study found that consuming the amount of caffeine in five or more cups of coffee a day doubled the risk of miscarriage. Coffee, colas, strong black tea, and chocolate are high in caffeine, as are some over-the-counter medications. A pregnant woman should limit her caffeine intake to no more than the equivalent of two cups of coffee per day.

Drugs

Some prescription drugs, such as some blood pressure medications, can harm the fetus, so they should be used only under medical supervision. Antidepressant use in pregnancy can lead to withdrawal symptoms in newborns after delivery. Newborns may become fussy, with high-pitched, irritable cries, and develop difficulty feeding. In rare cases, a mother's antidepressant use has been associated with persistent pulmonary hypertension in the infant. The antidepressant paroxetine has been shown to cause fetal cardiac defects. Medications to prevent seizures are associated with open neural tube defect and cleft palate-type birth defects. Because of concern over medication safety in pregnancy, both prescription and over-the-counter drugs should be used only under a physician's direction. Large doses of vitamin A, for example, can cause birth defects.

Recreational drugs, such as cocaine, are thought to increase the risk of miscarriage, stillbirth, growth abnormalities, major birth defects, and placental bleeding. Marijuana is associated with preterm birth and stillbirth. Methamphetamine use is associated with underweight babies.

STIs and Other Infections

Infections, including those that are sexually transmitted, are another serious problem for the fetus. The most common cause of life-threatening infections in newborns is group B streptococcus (GBS), a bacterium that can cause pneumonia, meningitis, and blood infections. About 25-30% of all pregnant women are carriers of GBS, so routine screening at 36 weeks of gestation is recommended. A carrier or a woman who develops a fever during labor will be given intravenous antibiotics at the time of labor to reduce the risk of passing GBS to her baby.

Syphilis is a preventable and curable disease. In pregnancy, untreated syphilis has a high rate of transmission to the fetus, resulting in severe adverse outcomes: stillbirth in 40% of cases, premature delivery, neonatal infection, fetal growth restriction, and congenital anomalies. Long-term consequences include deafness and neurologic impairment. Penicillin is the gold-standard treatment for syphilis.

Gonorrhea is reported to affect as many as 7% of pregnancies annually and is associated with increased risk for miscarriage and preterm birth. It is a major cause of blindness among newborns. Because gonorrhea is often asymptomatic, in many states the eyes of newborns are routinely treated with erythromycin ointment to destroy gonorrheal bacteria. In addition, because 50% of women with gonorrhea are also infected with Chlamydia trachomatis, detected cases should also be screened for chlamydia.

All pregnant women should be tested for hepatitis B, a virus that can pass from the mother to the infant at birth. Page 201Babies born to mothers with chronic hepatitis B should receive both the vaccine and protective antibodies (hepatitis B immune globulin) at birth.

Herpes simplex virus (HSV) can cause significant morbidity and mortality for neonates. It may damage the baby's eyes, skin, and brain, leading to death. Genital herpes can be transmitted to the baby if the mother is actively shedding virus at the time of delivery. In women with evidence of a genital outbreak, babies should be delivered by cesarean section to decrease the risk to the fetus. Women with a history of genital herpes should be prescribed suppressive therapy with acyclovir in the last month of pregnancy. A primary outbreak of herpes can be dangerous if it occurs during pregnancy because the virus may pass through the placenta to the fetus. For this reason, it is important to know if the pregnant woman or her partner has a history of herpes.

Nationwide, nearly 11,000 children under age 13 have been diagnosed with human immunodeficiency virus (HIV), the virus that causes AIDS. Of those, nearly 90% acquired the infection in utero during pregnancy, at birth, or during breastfeeding. Although shared needles from intravenous drug use can transmit HIV, most women acquire HIV/AIDS through heterosexual contact. The CDC therefore recommends routine testing for all pregnant women. Antiviral drugs, given to an HIV-infected mother during pregnancy and delivery and to her newborn immediately following birth, reduce the rate of HIV transmission from mother to infant from 25% to 2%. (See Chapter 18 for more about HIV and other STIs.)

In 2015, reports emerged about an outbreak of Zika virus among pregnant women in northern Brazil. Infection was associated with poor head growth in newborns (microcephaly). Since then, the mosquito-transmitted virus has spread throughout much of South America and Central America. In the United States, the Gulf Coast states, Puerto Rico, and Hawaii are at risk as well because they share similar mosquito habitats with the affected areas; as of September 2016, cases of locally acquired Zika (not related to travel) had been reported in Florida, Puerto Rico, and the U.S. Virgin Islands. Symptoms include headache, muscle and joint pains, rash, and eye redness.

Important concerns have surfaced regarding this new outbreak, especially because the CDC has established that the Zika virus causes birth defects, in particular, newborn microcephaly. What is the probability that a baby will be affected if the mother is infected with the virus? Answers will come from further research into the natural history, genetics, and virology of the Zika virus and affected mothers. The first people to test a vaccine are beginning their trials after approval by the FDA. In the meantime, CDC guidelines recommend preventive measures such as wearing long-sleeve shirts, using mosquito repellant, and, for all pregnant women, avoiding travel to areas with current outbreaks. Because Zika can be transmitted sexually, the CDC also suggests that couples use condoms or abstain from sexual activity if the man might have been exposed to Zika and if his sex partner is pregnant or could become pregnant. It is not yet clear how long a man may carry and transmit the virus after exposure. For more information, visit the CDC Zika website (www.cdc.gov/Zika).

Environmental factors affecting fetal or infant development are summarized in Table 8.2.

Table 8.2 Environmental Factors Associated with Problems in a Fetus or Infant
AGENT OR CONDITION
POTENTIAL EFFECTS
Accutane (acne medication)
Small head, mental impairment, deformed or absent ears, heart defects, cleft lip and palate
Alcohol
Unusual facial characteristics, small head, heart defects, mental impairment, defective joints
Chlamydia
Eye infections, pneumonia
Cigarette smoking
Miscarriage, stillbirth, low birth weight, respiratory problems, sudden infant death
Cocaine
Miscarriage, stillbirth, low birth weight, small head, and other major birth defects
Cytomegalovirus (CMV)
Small head, mental impairment, blindness
Diabetes (insulin-dependent)
Malformations of the brain, spine, and heart
Gonorrhea
Eye infection leading to blindness if untreated
Herpes
Brain damage, stillbirth
HIV infection
Impaired immunity, stillbirth
Lead
Reduced IQ, learning disorders
Marijuana
Impaired fetal growth, stillbirth
Mercury
Brain damage
Propecia (hair loss medication)
Abnormalities of the male sex organs
Radiation (high dose)
Small head, growth and mental impairment, multiple birth defects
Rubella (German measles)
Malformation of eyes or ears causing deafness or blindness; small head; mental impairment
Syphilis
Fetal death and miscarriage, prematurity, physical deformities
Tetracycline
Pigmentation of teeth, underdevelopment of enamel
Vitamin A (excess)
Miscarriage; defects of the head, brain, spine, and urinary tract
Zika
Microcephaly
Page 202
Prenatal Activity and Exercise

Physical activity during pregnancy contributes to mental and physical wellness (see the box "Physical Activity during Pregnancy"). Women can continue working at their jobs until late in their pregnancy, provided the work isn't so physically demanding that it jeopardizes their health. At the same time, pregnant women need more rest and sleep to maintain their own well-being and that of the fetus.

TAKE CHARGE: Physical Activity during Pregnancy

According to the U.S. Department of Health and Human Services's Physical Activity Guidelines Committee, more research is needed to fully assess the effects of regular physical activity on pregnant women. Most studies conclude that a well-managed routine of physical activity should result in no significant negative outcomes, such as low birth weight or early labor.

Maintaining a regular routine of physical activity throughout pregnancy can help a mother-to-be stay healthy and feel her best. Regular exercise can improve posture and decrease common pregnancy-related discomforts, such as backaches and fatigue. There is also evidence that physical activity may prevent gestational diabetes, relieve stress, and build stamina that can be helpful during labor and delivery.

A woman who was physically active before pregnancy should be able to continue her favorite activities in moderation, except for those that carry a risk of trauma, or unless there is a medical reason to reduce or stop exercise.

The American Congress of Obstetricians and Gynecologists (ACOG) offers advice regarding exercise during pregnancy. For example, downhill skiing or contact sports such as ice hockey, boxing, or soccer place pregnant women at risk for falls or abdominal trauma and should be avoided. Hot yoga and hot Pilates place the fetus at risk for overheating and are not recommended. In general, experts encourage low-impact aerobic activities such as walking or swimming over high-impact exercise. Physicians and pregnant women alike have concerns about exercise intensity. A good rule of thumb is never to exercise more than allows you to comfortably talk with a friend. If a pregnant woman is out of breath while exercising, she should slow down! Experts also recommend proper hydration and dressing to avoid overheating.

A woman who has never exercised regularly can safely start an exercise program during pregnancy after consulting with her health care provider. A routine of regular walking is considered safe. ACOG recommends that any pregnant woman who exercises should stop if she experiences any of the following warning signs:

Vaginal bleeding
Increased shortness of breath
Dizziness
Headache
Pain in the chest or calves
Regular painful contractions
Decreased fetal movement
Leakage of amniotic fluid
For detailed information about physical activity, see Chapter 13.

sources: American College of Obstetricians and Gynecologists. 2015. Committee Opinion No. 650: Physical activity and exercise during pregnancy and the postpartum period. Obstetrics and Gynecology 126(6): 1326-1327; Physical Activity Guidelines Advisory Committee. 2008. Physical Activity Guidelines Advisory Committee Report, 2008. Washington, DC: U.S. Department of Health and Human Services.
Kegel exercises, to strengthen the pelvic floor muscles, are recommended for pregnant women. These exercises are performed by alternately contracting and releasing the muscles used to stop the flow of urine. Each contraction should be held for about five seconds. Kegel exercises should be done several times a day for a total of about 50 repetitions daily.

Prenatal exercise classes are valuable because they teach exercises that tone the body muscles involved in birth, especially those of the abdomen, back, and legs. Toned-up muscles aid delivery and help the body regain its nonpregnant shape afterward.

Preparing for Birth

Childbirth classes are almost a routine part of the prenatal experience for both mothers and fathers today. These classes typically teach the details of the birth process as well as relaxation techniques to help deal with the discomfort of labor and delivery. The mother learns and practices a variety of techniques so that she will be able to choose what works best for her during labor when the time comes. The father or her partner typically acts as a coach, supporting her emotionally and helping her with her breathing and relaxing. He or she remains with the mother throughout labor and delivery, even when a cesarean section is performed.
COMPLICATIONS OF PREGNANCY AND PREGNANCY LOSS
Complications can arise in pregnancy for myriad reasons: maternal diseases and exposures such as diabetes, hypertension, or tobacco use; placental factors, including abruption Page 203or placenta previa; or fetal conditions such as genetic conditions like Down syndrome or cystic fibrosis. Each complication benefits from early diagnosis, counseling, and, if possible, corrective action.

Ectopic Pregnancy

In an ectopic pregnancy, the fertilized egg implants and begins to develop outside the uterus, usually in an oviduct (Figure 8.6). As the limited space of the oviduct cannot accommodate the rapid growth of a fertilized egg, ectopic pregnancies pose high risk of emergent bleeding through tubal rupture. Although ectopic pregnancies account for only 2% of all pregnancies, they contribute to 6% of all maternal deaths.


FIGURE 8.6 Ectopic pregnancy in a fallopian tube.
Ectopic pregnancies usually occur because of occlusion (blockage) of the fallopian tube, most often as a result of pelvic inflammatory disease, although smoking also increases a woman's risk for ectopic pregnancy. The embryo may spontaneously abort, or the embryo and placenta may continue to expand until they rupture the oviduct. Sharp pain on one side of the abdomen or in the lower back, usually in about the seventh or eighth week of pregnancy, may signal an ectopic pregnancy, and there may be irregular bleeding. If bleeding from a rupture is severe, the woman may go into shock, characterized by low blood pressure, a fast pulse, weakness, and loss of consciousness.

Surgical removal of the embryo and the oviduct may be necessary to save the mother's life, although microsurgery can sometimes be used to repair the damaged oviduct. If diagnosed early, before the oviduct ruptures, ectopic pregnancy can often be treated successfully without surgery with the chemotherapeutic agent methotrexate.

Spontaneous Abortion

A spontaneous abortion, or miscarriage, is the termination of pregnancy before the 20th week. Most miscarriages—about 60%—are due to chromosomal abnormalities in the fetus. Certain occupations that involve exposure to chemicals or radiation may increase the likelihood of a spontaneous abortion.

Vaginal bleeding (spotting) is usually the first sign that a pregnant woman may miscarry. She may also develop pelvic cramps, and her symptoms of pregnancy may disappear. Mild cramping, however, is common in pregnancy and is usually not associated with miscarriage.

One miscarriage doesn't mean that later pregnancies will be unsuccessful, and about 70-90% of women who miscarry eventually become pregnant again. About 1% of women suffer three or more miscarriages, possibly because of anatomical, hormonal, genetic, or immunological factors.

Stillbirth

The terms fetal death, fetal demise, stillbirth, and stillborn all refer to the delivery of a fetus that shows no signs of life. Each year over 3 million stillbirths occur worldwide. In the United States, the stillbirth rate is a little more than 6 in 1000. Risk factors for stillbirth include smoking, advanced maternal age, obesity, multiple gestations, and chronic disease. Race is also a factor; black women have twice as many stillbirths as white women. Although some observers attribute the increased risk for stillbirth among black women to the corresponding increased risk of preterm delivery, other reasons for race-based health care disparities may include poor access to care, infection, and the combined effects of racism and poverty.

Preeclampsia

A disease unique to pregnancy, preeclampsia is characterized by elevated blood pressure and the appearance of protein in the urine. Left untreated, preeclampsia will worsen over time, resulting in symptoms including headache, right upper-quadrant abdominal pain, vision changes (referred to as scotomata), and notable increased swelling and weight gain. One of the most severe outcomes of untreated preeclampsia is the onset of seizures, a condition called eclampsia. Other potential complications of preeclampsia are liver and kidney damage, bleeding, fetal growth restriction, and even fetal death.

The incidence of preeclampsia is commonly cited to be about 5%, but wide variations are reported. In high-income countries, the incidence varies from 1.6 to 10 per 10,000 deliveries, with a mortality rate of less than 1%. In low- and middle-income countries, preeclampsia is a leading cause of maternal and fetal complications. The incidence is related to Page 204race and ethnicity as well as to environmental factors and family history. It affects women of all reproductive ages.

Women with preeclampsia without severe features may be monitored closely as outpatients. More severe cases may require hospitalization for close medical management and early delivery.

Placenta Previa

In placenta previa, the placenta either completely or partially covers the cervical opening, preventing the mother from delivering the baby vaginally. As a result, the baby must be delivered by cesarean section. This condition occurs in 1 in 250 live births. Risk factors include prior cesarean delivery, multiple pregnancies, intrauterine surgery, smoking, multiple gestations, and advanced maternal age. The first indication of previa not detected by ultrasound is often painless bright red vaginal bleeding with or without contractions. Previa is the attributed cause of 20% of bleeding in the third trimester.

Placental Abruption

In placental abruption, a normally implanted placenta separates prematurely from the uterine wall. Patients experience abdominal pain, vaginal bleeding, and uterine tenderness. This causes 30% of all bleeding in the third trimester. The condition also increases the risk of fetal death. The risk factors for developing a placental abruption are maternal age, smoking, cocaine use, multiple gestation, trauma, preeclampsia, hypertension, and premature rupture of membranes.

Gestational Diabetes

During gestation, about 7-18% of all pregnant women develop gestational diabetes mellitus (GDM), in which the body loses its ability to use insulin properly. In these women, diabetes occurs only during pregnancy. The condition stems from the secretion of placental hormones: growth hormone, cortisol, placental lactogen, and progesterone. GDM arises when pancreatic function is not sufficient to overcome the insulin resistance created by these pregnancy-related hormones. Women diagnosed with GDM have an increased risk of developing type 2 diabetes later in life. It is important to accurately diagnose and treat GDM because it can lead to preeclampsia, polyhydramnios (increased levels of amniotic fluid), large fetuses, birth trauma, operative deliveries, perinatal mortality, and neonatal metabolic complications.

All women in pregnancy are therefore advised to test for GDM, which is a simple and straightforward procedure. The woman will be asked to drink a sugary beverage. After a set period of time in which she consumes nothing else, her glucose level is assessed. If the body processes the sugars normally, the blood sugar should be low. In the case of GDM, the sugars remain high. When a diagnosis of GDM is made, treatment can be in the form of diet and exercise modification, or medication.

Preterm Labor and Birth

When a pregnant woman goes into labor before the 37th week of gestation, she is said to experience preterm labor. Preterm labor is one of the most common reasons for hospitalizing pregnant women, but verifying true preterm labor can be difficult, and stopping it is even harder. About 30-50% of preterm labors resolve themselves, with the pregnancy continuing to full term.

Around the world, an estimated 13 million babies are born prematurely—before 37 completed weeks of gestation—each year. In 2014, 9.6% of babies were born prematurely in the United States. The rate has declined 8% since a high in 2007. Preterm birth rates vary widely among racial and ethnic groups.

Preterm birth is the leading direct cause of newborn death, accounting for about one-third of all infant deaths. Preterm birth is also the main risk factor for newborn illness and death from other causes, particularly infection. Babies born prematurely appear to be at a higher risk of long-term health and developmental problems, including delayed development and learning problems.

Currently, the underlying causes for preterm labor remain poorly identified and require further research. Established risk factors for preterm birth include lack of prenatal care, smoking, drug use, stress, personal health history, infections or illness during pregnancy, obesity, exposure to environmental toxins, a previous preterm birth, and the carrying of multiple fetuses. However, only about half the women who give birth prematurely have any known risk factors.

Labor Induction

If pregnancy continues well beyond the baby's due date, it may be necessary to induce labor artificially. This is one of the most common obstetrical procedures and is typically offered to pregnant women who have not delivered and are 7-14 days past their due dates.

Low Birth Weight and Premature Birth

A low-birth-weight (LBW) baby is one that weighs less than 5.5 pounds at birth. LBW babies may be premature Page 205(born before the 37th week of pregnancy) or full-term. Babies who are born small even though they're full-term are referred to as small-for-dates or small-for-gestational-age babies. Low birth weight affected 8.1% of babies born in the United States in 2015. About half of all cases are related to teenage pregnancy, cigarette smoking, poor nutrition, and poor maternal health. Other maternal factors include drug use, stress, depression, and anxiety. Adequate prenatal care is the best way to prevent LBW.

Full-term LBW babies tend to have fewer problems than premature infants. In the United States in 2015, 9.6% of babies were born prematurely. Many of the premature infant's organs are not sufficiently developed. Even mild prematurity increases an infant's risk of dying in the first month or year of life. Premature infants are subject to respiratory problems and infections. They may have difficulty eating because they may be too small to suck a breast or bottle and their swallowing mechanism may be underdeveloped. As they get older, premature infants may have problems such as learning difficulties, behavior problems, poor hearing and vision, and physical awkwardness.

Infant Mortality

The U.S. rate of infant mortality, the death of a child at less than 1 year of age, is near its lowest point ever—5.8 deaths for every 1000 live births as of 2014; however, that number remains far higher than rates in most of the developed world. Poverty and inadequate health care are key causes, with rates rising in poorer communities and lowest in areas of wealth. The infant mortality rate among African Americans is 2.4 times higher than that among Euro-Americans.

Forty-six percent of infant deaths are due to one of three leading factors: congenital abnormalities, prematurity/low birth weight, or sudden infant death syndrome (SIDS). SIDS is defined by a sudden and unexpected death of a child less than 1 year of age not explained by thorough investigation including autopsy. More than 1500 babies died of SIDS in 2014, the latest year for which statistics are available.

Prior to the 1990s, parents often put their babies to sleep on their stomachs, and the rate of SIDS was 3.5 per 1000. In 1994, however, evidence supported the introduction of the "Back to Sleep" campaign, which suggested that putting babies to bed on their backs rather than on their stomachs significantly reduces the risk of SIDS. Research suggests that abnormalities in the brain stem, the part of the brain that regulates breathing, heart rate, and other basic functions, underlie the risk for SIDS. Risk is increased greatly for infants with these innate differences if they are exposed to environmental risks such as tobacco smoke, alcohol, substance use, and, most important, sleeping stomach-side down. Because infants developmentally change how they sleep between 2 and 4 months of age, this is a time period of particular risk. Additionally, suffocation risk increases with the presence of many items common to cribs: fluffy pillows, mattresses, or plush toys. Therefore, current recommendations are to place babies to sleep back down, on a firm sleep surface, without soft bedding, plush toys, or additional clothing that might cause overheating. Parental avoidance of tobacco smoke, alcohol, and illicit drugs is important. Several studies have found that the use of a pacifier significantly reduces the risk of SIDS.

Coping with Loss

Parents form a deep attachment to their children even before birth, and those who lose an infant before or during birth usually experience deep grief. Initial feelings of shocked disbelief and numbness may give way to sadness, anger, crying spells, and preoccupation with the loss. Physical sensations such as tightness in the chest or stomach, loss of appetite, and sleeplessness may also occur. For the mother, physical exhaustion and hormone imbalances can compound the emotional and physical stress.

Experiencing the pain of loss is part of the healing process. Use of support groups or professional counseling is often helpful. Planning the next pregnancy, with a physician's input, can be an important step toward recovery, but often a couple is physically fertile before either has emotionally healed from the loss. Subsequent pregnancies are often marked by anxiety or renewed grief.

Ask Yourself

QUESTIONS FOR CRITICAL THINKING AND REFLECTION
Do you know anyone who has lost a child to miscarriage, stillbirth, or a birth defect? If so, how did they cope with their loss? What would you do to help someone in this situation?
CHILDBIRTH
By the end of the ninth month of pregnancy, most women are tired of being pregnant; both parents are eager to start a new phase of their lives. Most couples find the actual process of birth to be an exciting and positive experience.

Choices in Childbirth

Many parents-to-be today can choose the type of practitioner and the environment they want for the birth of their child. A high-risk pregnancy is best handled by a specialist physician, but for low-risk pregnancies, many options are available.Page 206

In 2014, 98.5% of babies in the United States were delivered in hospitals. Physicians performed 91.4% of all deliveries, and certified nurse-midwives performed about 8% of them. Although physicians typically deliver in hospital settings, nurse-midwives may attend deliveries in freestanding birth centers where the environment may feel more comfortable while still remaining close to the medical resources of a hospital.

Many mothers-to-be are accompanied in the delivery room by a labor companion, called a doula. A doula is a woman who either has been through childbirth or has experience with birth. She stays with the laboring woman and provides support, information, and advocacy. Supportive labor companions may improve labor progress by reducing maternal anxiety. Studies suggest that the presence of a knowledgeable doula may shorten the duration of labor, increase the rate of spontaneous vaginal birth, and reduce the use of narcotic painkillers, forceps delivery, and cesarean birth.

In 2014, 1.5% of American women elected to give birth at home or in birth facilities that offer low-technology care. In 2011, ACOG recommended against homebirth. The American Academy of Pediatrics notes that, although hospital or freestanding accredited birth centers are the safest place to give birth, every infant should have access to the birth setting that is best for him or her. However, the American College of Nurse-Midwives supports out-of-hospital births for low-risk, healthy women. There is significant controversy on this topic. The absolute risk for infant mortality is low in either setting, but it is increased two- to threefold in the setting of homebirth. For some people, this is an acceptable risk; for others, it is not.

Health care providers will need to assess maternal and fetal health and make decisions together with prospective parents about appropriate care providers and location. Prospective parents should discuss all aspects of labor and delivery with their provider beforehand so that they can learn what to expect and can state their preferences.

Labor and Delivery

The birth process occurs in three stages (Figure 8.7). Labor begins when hormonal changes in both the mother and the baby cause strong, rhythmic uterine contractions to begin. These contractions exert pressure on the cervix and cause the lengthwise muscles of the uterus to pull on the circular muscles around the cervix, causing effacement (thinning) and dilation (opening) of the cervix. The contractions also pressure the baby to descend into the mother's pelvis, if it Page 207hasn't already. The entire process of labor and delivery usually takes between 2 and 36 hours, depending on the size of the baby, the baby's position in the uterus, the size of the mother's pelvis, the strength of the uterine contractions, the number of prior deliveries, and other factors. The length of labor is generally shorter for second and subsequent births.


FIGURE 8.7 Birth: labor and delivery. (a) The first stage of labor; (b) the second stage of labor: delivery of the baby; (c) the third stage of labor: expulsion of the placenta.
The First Stage of Labor

The first stage of labor averages 13 hours for a first birth, although there is wide variation among women. It begins with cervical effacement and dilation and continues until the cervix is completely dilated. Contractions usually last about 30 seconds and occur every 15-20 minutes at first. They occur more often later. The prepared mother relaxes as much as possible during these contractions to allow labor to proceed without being blocked by tension. Early in the first stage, a small amount of bleeding may occur as a plug of slightly bloody mucus that blocked the opening of the cervix during pregnancy is expelled. In some women, the amniotic sac ruptures and the fluid rushes out; this is sometimes referred to as "breaking the bag of water."

The last part of the first stage of labor, called active labor, is characterized by strong and frequent contractions, much more intense than in the early stages of labor. Contractions may last 60-90 seconds and occur every 1-3 minutes. During active labor the cervix opens completely, to a diameter of about 10 centimeters. When the head of the fetus is flexed forward, to present its smallest diameter, it measures 9-10 centimeters. Therefore, a completely dilated cervix should permit the passage of the fetal head.

The Second Stage of Labor

The second stage of labor is the "pushing phase." It begins with complete cervical dilation and ends with the delivery of the baby. With uterine contractions and maternal pushing, the baby descends through the bones of the pelvis, past the cervix, and into the vagina, which it stretches open. Some women find this the most difficult part of labor; others find that the contractions and bearing down bring a sense of relief. The baby's head and body turn to fit through the narrowest parts of the passageway, and the soft bones of the baby's skull move together and overlap as it is squeezed through the pelvis. When the top of the head appears at the vaginal opening, the baby is said to be crowning.

As the head of the baby emerges, the physician or midwife will check to ensure that the umbilical cord is not around the neck. With a few more contractions, the baby's shoulders and body emerge. As the baby is squeezed through the pelvis, cervix, and vagina, amniotic fluid in the lungs is forced out by the pressure on the baby's chest. Once this pressure is released as the baby emerges from the vagina, the chest expands and the lungs fill with air for the first time. The baby will appear wet and often is covered with a cheesy substance called vernix. The baby's head may be oddly shaped at first, due to the molding of the soft plates of bone during birth, but it usually takes on a more rounded appearance within 24 hours.

The Third Stage of Labor

In the third stage of labor, the uterus continues to contract until the placenta is expelled. This stage usually takes 5-30 minutes. The entire placenta must be expelled; if part remains in the uterus, it may cause bleeding and infection. Breastfeeding soon after delivery helps control uterine bleeding because it stimulates secretion of a hormone that makes the uterus contract.

The baby's physical condition is assessed with the Apgar score, a formalized system for assessing the baby's physical condition and whether medical assistance is needed. Heart rate, respiration, color, reflexes, and muscle tone are rated individually with a score of 0-2, and a total score between 0 and 10 is given at 1 and 5 minutes after birth. A score of 7-10 at 5 minutes is considered normal. Most newborns are also tested for 29 specific disorders, some of which are life-threatening. The American Academy of Pediatrics endorses these tests, but they are not routinely performed in every state.

Pain Relief during Labor and Delivery

Women vary in how much pain they experience in childbirth. First babies are typically the most challenging to deliver because the birth canal has never stretched to this extent before. It is recommended that women and their partners learn about labor and what kinds of choices are available for pain relief. Childbirth preparation courses are a good place to start, and communicating with one's obstetrician or midwife is essential to assessing pain relief options. Pain can be modified by staying active in labor, laboring in water, and using breathing and relaxation techniques including hypnosis.

Medical pain relief can come in the form of intravenous narcotics, which are short-acting and can be used only in early labor. If a baby is born under the influence of narcotics, it can appear floppy and without vigor. The most commonly used medical intervention for pain relief is the epidural injection. This procedure involves placing a thin plastic catheter between the vertebrae in the lower back. Medication that reduces the transmission of pain signals to the brain is given through this catheter. Regional anesthetic drugs are given in low concentration to minimize weakening of the leg muscles so that the mother can push effectively during the birth. The advantage of the epidural is that the medication is used in low amounts in the confined space of the spinal column, protecting the fetus from the effect of the medication. The mother is awake and is an active participant in the birth.

Local anesthesia is available for repair of any tear or episiotomy (a surgical incision of the perineum to allow Page 208easier delivery of the baby) if the mother has not used an epidural for the labor.

Cesarean Delivery

In a cesarean section, the baby is removed through a surgical incision in the abdominal wall and uterus. Cesarean sections are necessary when a baby cannot be delivered vaginally—for example, if the baby's head is bigger than the mother's pelvis or if the baby is not head down at the time of labor. If the mother has a serious health condition such as high blood pressure, a cesarean may be safer for her than labor and a vaginal delivery. Cesareans are more common among women who are overweight or have diabetes. Other reasons for cesarean delivery include abnormal or difficult labor, fetal distress, and the presence of a dangerous infection like herpes that can be passed to the baby during vaginal delivery.

Repeat cesarean deliveries are also very common. In 2014, 88.7% of American women who had had one child by cesarean had subsequent children delivered the same way. Although the risk of complications from a vaginal delivery after a previous cesarean delivery is low, there is a small (1%) risk of serious complications for the mother and baby if the previous uterine scar opens during labor (uterine rupture). For this reason, women and their physicians may choose to deliver by elective repeat cesarean.

Cesarean section is the most common hospital procedure performed in the United States. High rates have prompted health officials to examine ways to reduce cesarean sections, leading to a successful reduction over the past years. The safest mode of delivery for both mother and baby in an uncomplicated pregnancy is a vaginal delivery. Like any major surgery, cesarean section carries a longer recovery period and additional risks. Most cesarean deliveries are performed with regional anesthetic, which permits the mother to remain awake for the surgery with her partner present.

QUICK STATS

32.0% of American babies born in 2015 were delivered by cesarean section.

—Centers for Disease Control and Prevention, 2016
The Postpartum Period

The postpartum period, a stage of about three months following childbirth, is a time of critical family adjustments. Parenthood begins literally overnight, and the transition can cause considerable stress.

Following a vaginal delivery, mothers usually leave the hospital within one or two days (after a cesarean section, they usually stay an additional day). Uterine contractions will occur from time to time for several days after delivery, especially during nursing, as the uterus begins to return to its prebirth size. It usually takes six to eight weeks for a woman's reproductive organs to return to their prebirth condition. She will have a bloody discharge called lochia for three to six weeks after the birth.

Within the first few days after birth, a baby will undergo screening for certain genetic conditions such as sickle-cell disease; the mandated tests vary by state. The baby's head—if somewhat cone-shaped following a vaginal delivery—will become more rounded within a few days. It takes about a week for the umbilical cord stump to shrivel and fall off. Regular infant checkups for health screenings and immunizations usually begin when the infant is only a few weeks old.

Ask Yourself

QUESTIONS FOR CRITICAL THINKING AND REFLECTION
If you are a woman, what are your views on labor and delivery options? If you have a child in the future, which facility, delivery, and pain management options do you think you would prefer? If you are a man, what are your views on participating in delivery? What steps do you think could be taken to help new mothers at home? In the workplace?
Breastfeeding

Lactation, the production of milk, begins about three days after childbirth. Prior to that time (sometimes as early as the second trimester), colostrum is secreted by the nipples. Colostrum contains antibodies that help protect the newborn from infectious diseases; it is also high in protein.

The American Academy of Pediatrics recommends breastfeeding exclusively for six months, then in combination with solid food until the baby is one year of age, and then for as long after that as a mother and baby desire. Currently only 22.3% of U.S. mothers breastfeed exclusively for six months. Human milk is perfectly suited to the baby's nutritional needs and digestive capabilities, and it supplies the baby with antibodies. Breastfeeding decreases the incidence of infant infection and diarrhea and appears to decrease diabetes and childhood obesity.

Breastfeeding is beneficial to the mother as well. It stimulates contractions that help the uterus return to normal more rapidly, contributes to postpregnancy weight loss, and may reduce the risk of breast and ovarian cancers. Nursing also provides a sense of closeness and emotional well-being for mother and child. Less infection means more productive parents. Parents are able to miss less work. Page 209Avoiding formula is cost saving and good for the environment. For women who want to breastfeed but who have problems, help is available from support groups, books, or lactation consultants and health care providers.


Breastfeeding can enhance the bond between mother and child. The American Academy of Pediatrics recommends breastfeeding exclusively for six months and then in combination with solid food until the baby is at least one year of age.
© KidStock/Getty Images
Some women find breastfeeding difficult due to physical or social problems. Some do not have enough milk or the milk will not circulate properly. Sometimes babies refuse to nurse at the breast. Tenderness or infection of the nipples can also be prohibitive. If a woman has an illness or requires drug treatment, she may have to bottlefeed her baby because drugs and infectious agents may show up in breast milk. Working mothers encounter varying degrees of support from their employers.

An advantage to bottlefeeding is that it is easier to tell how much milk an infant is taking in, and bottlefed infants tend to sleep longer. Bottlefeeding also allows the father or other caregiver to share in the nurturing process. Both breastfeeding and bottlefeeding can be part of loving, secure parent-child relationships.

When a mother doesn't nurse, menstruation usually begins within about 10 weeks. Breastfeeding can prevent the return of menstruation for six months or longer because the hormone prolactin, which aids milk production, suppresses hormones vital to the development of mature eggs. However, ovulation—and pregnancy—can occur before menstruation returns, so breastfeeding is not a reliable contraceptive method. If a woman wishes to avoid pregnancy, she should use a reliable method of birth control. If the mother becomes pregnant while still nursing, she needs to make sure that she is receiving adequate nutrition because the energy requirement for both breastfeeding and gestating is immense. With proper counseling, breastfeeding can continue until near delivery.

Postpartum Depression

The physical stress of labor, blood loss, fatigue, decreased sleep, fluctuating postpartum hormone levels, and anxieties of becoming a new parent all contribute to emotional instability postpartum. About 50-80% of new mothers experience "baby blues," characterized by episodes of sadness, weeping, anxiety, headache, sleep disturbances, and irritability. A mother may feel lonely and anxious about caring for her infant.

About 9-16% of new mothers experience postpartum depression. Postpartum depression is characterized by a prolonged period of anxiety, guilt, fear, or self-blame; these feelings prevent the new mother from normal participation in everyday life or the normal care of her newborn. Those close to the affected woman may fear for the well-being of the mother or those in her care. Fortunately, postpartum depression can be prevented and treated effectively. Women with a history of depression or depression during pregnancy can benefit from early referral to an appropriate mental health care provider. Rest is a key component of recovery. The mother's support system should offer to take on important responsibilities to allow the mother to rest and recover, as well as encourage her to continue outside interests and share her concerns with a professional who can assess the need for medical therapy.

Some men also seem to get a form of postpartum depression, characterized by anxiety about their changing roles and feelings of inadequacy. Both mothers and fathers need time to adjust to their new roles as parents.

Attachment

Another feature of the postpartum period is the development of attachment—the strong emotional tie that grows between the baby and the adult who cares for the baby. Parents can foster secure attachment relationships in the early weeks and months by responding sensitively to the baby's true needs. Parents who respond appropriately to the baby's signals of gazing, looking away, smiling, and crying establish feelings of trust in their child. They feed the baby Page 210when she's hungry, for example; respond when she cries; interact with her when she gazes, smiles, or babbles; and stop stimulating her when she frowns or looks away. A secure attachment relationship helps the child develop and function well socially, emotionally, and mentally.

For most people, the arrival of a child creates a deep sense of joy and accomplishment. However, adjusting to parenthood requires effort and energy. Talking with friends and relatives about their experiences during the first few weeks or months with a baby can help prepare new parents for the period when the baby's needs may require all the energy that both parents have to expend. But the pleasures of nurturing a new baby are substantial, and many parents look back on this time as one of the most significant and joyful of their lives.

Ask Yourself

QUESTIONS FOR CRITICAL THINKING AND REFLECTION
What are some early signs or symptoms of depression? Consider ways you might start a conversation about depression or help a new mother find access to help. What kind of things might you say or do?