Formed at 23 days when the primary yolk sac is pinched off by the extraembryonic coelom
secondary yolk sac
Length of time calculated from the first day of the last normal menstrual period to the point at which the pregnancy is being assessed
High-frequency transducer that is inserted into the vaginal canal to obtain better definition of first-trimester pregnancy.
Hormone secreted by the trophoblastic cells of the blastocyst; laboratory test indicates pregnancy when values are elevated
human chorionic gonadotropin
Interface between the decidua capsularis and the echogenic, highly vascular endometrium
double decidual sac sign
Cavity in which the fetus exists; forms early in gestation; fills with amniotic fluid to protect the fetus
Invasive diagnostic genetic testing that involves sampling zygotic cells from developing placental tissue
chorionic villi sampling
Clinicians and sonographers use ________ to date the pregnancy, with the first day of the last menstrual period as the beginning of gestation.
The gestational age (age known as postmenstrual age) is calculated by adding ____ weeks to conceptual age.
The fertilized ovum, which now should be referred to as a ________, undergoes rapid cellular division to form the 16-cell morula.
The blastocyst typically enters the uterus 4-5 days after fertilization, with implantation occurring _______ days after ovulation.
Although the organ function remains as minimal, the ________ system is the first organ to develop rapidly, with the first heartbeats noted between 5.5 and 6.5 weeks
After 8 weeks, hCG levels ________ and subsequently decline while the gestational sac continues to grow.
A normal gestational sac can be consistently demonstrated when the hCG level reanges between __________mIU/mL.
The sonographer must be aware that when the hCG level is elevated and the gestational sac is not seen within the uterus, an ________ pregnancy should be considered.
The interface between the decidua capsularis and the echogenic, highly vascularized endometrium forms the _____________________
double decidual sac
The first intragestational sac anatomy seen is the sonographic ________ sac, which is routinely visualized between 5 and 5.5 weeks' gestation.
The spine is also developing during the embryonic period, particularly in the ________ weeks of gestation.
The embryonic face undergoes significant evolution starting in the 5th week of gestation, with palate fusion beginning around the_______ week of gestation
At approximately 10 weeks' gestation, the midgut loop continues to grow and rotate before it descends into the fetal abdomen at about the _____ week
The cystic rhomboid fossa can sonographically be imaged routinely from the _______ week of gestation.
It is important to note that the________ventricles completely fill the cerebral vault at this time in gestation
Sonographically, the gestational sac size or mean sac diameter (MSD) is determine by calcalation the average sum of the________,________, and _______ of the gestational sac.
length, width, height
4. developing follicle
Label the diagram of normal conception
2. connecting stalk
3. emrbyonic disc
4. yolk sac
6. chorionic cavity
7. amniotic sac
8. umbilical card
9. yolk sac
11. connecting stalk
12. yolk sac
13. chorionic cavity
14. smooth chorion
16. amniotic sac
17. umbilical cord
18. yolk sac remnant
label the development of amnion, yolk sac, and embryo
gestational sac(chorionic cavity)
Identify the sonographic findings in this 5-week intrauterine gestation
curved arrow: amniotic membrane
straight arrows: umbilical cord
In this 8-week gestation, name the structure that the curved arrow is pointing to. Name the structure that the straight arrows are pointing to.
Failure to visualize the yolk sac, with a minimum of _____ mm MSD, using transvaginal sonography, should provoke suspicion of abnormal pregnancy.
Transabdominal studies have shown that the yolk sac should be seen within mean sac diameters of _______ mm and should always be visualized with a mean sac diameter of 20 mm.
The growth rate of the yolk sac has been reported to be approximately ______ mm per millimeter of growth of the MSD when the MSD is less that 15 mm.
The early embryo is not identified with transvaginal sonography until heart motion is detected and the crown-rump length measures approximately _____ mm.
At _______ weeks, three primary vesicles are seen within the fetal brain: the prosencephalon, the mesencephalon, and the rhomencephalon.
During development, the midgut loop of the bowel continues to grow and rotate before it descends into the fetal abdomen at about the_____ week.
Using transvaginal sonography, multiple gestations can readily be diagnosed at very early stages, between ________ weeks
5.5 & 6.5
Sonographically, dichorionic and diamniotic twins appear as _____ separate gestational sacs with individual trophoblastic tissue, which allows the appearance of a thick dividing membrane.
Monochorionic-diamniotic twins appear to be contained within _______ chorionic sac; _____ amnion(s); ______ yolk sac(s), and two embryos are identified.
one, two, two, two
The monozygotic, monoamniotic-monodichorionic twin gestation shows _____ gestational sac with _____ amniotic membrane, which may contain one or two yolk sacs and two-embryos within the simgle amniotic membrane.
Measurement that includes both fetal orbits at the same time to predict gestational age
Used in the first trimester to estimate appropriate gestational age with menstrual dates
gestational sac diameter
Method whereby the fetus is categorized into small, average, or large growth percentile
growth-adjusted sonar age
Fetal transverse cranial diameter at the level of the thalamus and cavum septum pelluciidum
Most accurate measurement for determining gestational age; made in the first trimester
Measurement at the level of the stomach, left portal vein, and left umbilical sign
Fetal head is relatively narrow in the transverse plane and is elongated in the anteroposterior plane
Fetal head is relatively wide in the transverse diameter and shortened in the anteroposterior plane
Condition in which fetus is not growing as fast as normal; usually considered malnourished or abnormal
intrauterine growth restriction (IUGR)
Sonographically, the earliest sign of intrauterine pregnancy is the _______, which appears an echogenic, thickening filling of the fundal region of the endometrial cavity occurring at approximately 3-4 weeks' gestation.
At 5 weeks, the average of the three perpendicular internal diameters of the gestational sac, calculateed as the mean of the _______ diameter, the ________ diameter, and the _______ diameter, can provide an adequuate estimation of menstrual age.
anteroposterior, transverse, longitudinal
when the gestational sac exceeds _______ mm in mean internal diapeter, a yolk sac should be seen.
Normal yolk sac size should be less than _____ mm; greater than _____ mm has been associated with poor pregnancy outcome
When the mean gestational sac diameter exceeds ____ mm, an embryo with definite cardiac activity should be well visualized with transvaginal scanning.
The embryonic echoes can be identified as early as 38-39 days menstrual age, and the CRL is usually ______ mm at this age.
The most accurate sonographic technique for establishing gestational age in the first trimester is
Absence of an embryo by 7-8 weeks' gestation is consistent with an embryonic demise or an _______ pregnancy
If a nomogram is not readily available to identify gestational age, a convenient formula is gestational age is weeks equals _______.
CRL in cm + 6
In the second trimester, the gestational age parameters extend to ______ diameter, ______circumference, _______ circumference, and ______ length.
biparietal, head, abdominal, femur
Growth of the fetal skull slows from ____ mm per week in the second trimester to _____ mm per week in the third trimester.
The fetal head should be imaged in a transverse ________ section, ideally with the fetus in a direct occiput transverse position.
The BPD should be measured perpendicular to the fetal skull at the level of the ________ and ________.
thalamus, cavum septi pellucidi
Intracranial landmarks should include the ________ anteriorly and posteriorly, the ________ anteriorly in the midline, and the ________ in the atrium of each lateral ventricle.
falx, cavum septi pellucidi, choroid plexus
The head shape should be ________, not round, because this can lead to overestimation of gestational age, just as a flattened or compressed head can lead to underestimation of gestational age
The calipers should be placed from the ________ edge of the parietal bone to the ________ edge of the opposite parietal bone, or "outer edge to inner edge."
The proper coronal view should be ________ to the standard transverse HC view passing through the thalamus.
One can ________ gestational age from a dolichocephalic head or ________ with brachycephaly.
The AC is very useful in monitoring normal fetal growth and detecting fetal growth disturbances, such as IUGR, and macrosomia; however, it is more useful as a ________ than in predicting gestational age.
The fetal abdomen should be measured in a transverse plane at the level of the ________ where the ________ vein branches into the left portal sinus.
The abdomen should be more ________ than oval because an oval shape indicates an oblique cut resulting in a false estimation of size.
The ________ length is an especially useful parameter that can be used to date a pregnancy when a fetal head cannot be measured because of position, or when there is a fetal head anomaly.
Often an echo from the near side of the cartilaginous distal femoral condyles will be seen, call the "________"; this should not be included in the measure of the diaphysis.
distal femoral point
The tibia and fibula can be measured by first identifying the ________, then following it down until the two parallel bones can be identified
Humerus length is sometimes more difficult to measure than the femur length because the humerus usually is found very close to the fetal ________ but can exhibit a wide range of motion.
The ulna can be distinguished from the radius because it penetrates much more deeply into the ________.
yolk sac, 4 weeks gestational age
Identify the small structure within the gestational sac and estimate the gestational age
sp=spine, st=stomach, abdominal circumference
Identify the labeled structures in this image
Which measurement is being made at this level?
distal femoral point, femur
Name the structure the arrow is pointing to.
name the structure being measured
Follicle that releases mature ovum hemorrhages and collapses to for the corpus luteum and secretes ________ and _________
The blostocyst contains trophoblastic cells and "inner mass". This later forms the ________
During implantation, protoelytic enzymes produced by trophoblasts "eat into" decidual tissue. This creates spaces for _____________.
At approzimately 23 days menstrual age, primary yolk sac is pinched off, forming _____________, which is what is seen sonographically.
secondary yolk sac
The cardiovascular system undergoes rapid development, with initial heartbeat occurring between __________ weeks.
The last two weeks of the first trimester (weeks _______) constitute the beginning of the fetal period.
11 & 12
The decidua basalis is closest to the ________, and the decidua capsularis is closest to the ________.
The gestational sac should appear round or oval. If elongated or angled, this is __________
Fusion of membranes, known as _________, occurs at approximately ___________ weeks.
chorioamniotic fusion, 14-15
Developing spine may be visualized sonographically as _______ ___________ lines at 6 weeks gestation
Identify labelled structures in this illustration of a 40 day old embryonic brain
spine demonstrated by parallel echogenic lines with a sonolucent center
Identify which structure the arrow is pointing to in this sonogram of an 8-week embryo
By 8 weeks, three primary vessels are seen within the fetal brain: the prosencephalon, the mesencephalon, and the _________
The rhombencephalon is divided into two segments, the cephalic portion, or ________ and the caudal component, or _________
Sonographically, limb buds may be detected from the ______ week on. _______ limbs form first