Prenatal- ABMG Case Examples

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All of the following are indications for prenatal diagnosis except:

A. History that the patient has been treated in the past with chemotherapy for Hodgkin's disease
B. Previous child with autosomal trisomy
C. Either parent a carrier of a chromosomal translocation
D. Previous child with Tay-Sachs disease

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Terms in this set (24)

A

Not an indication for prenatal diagnosis. Studies had not shown an increase risk of chromosomal abnormalities or other birth defects following successful therapy for childhood cancers.

Traditional amniocentesis is:

A. Associated with a 5% risk of causing miscarriages
B. Performed at 16-18 weeks gestation
C. Contraindicated if the patient has genital herpes
D. Associated with a risk of causing clubfoot of 1.5%

Correct: B

Traditional amniocentesis is normally performed at 16-18 weeks gestation.

Chorionic villus sampling is:

A. Less likely to cause miscarriage than traditional amniocentesis
B. Associated with a 4-fold increased risk of transverse limb abnormalities
C. Complicated by a mosaic result in 1-2% of cases
D. Indicated for couples who have a previous child with a neural tube defect

Correct: C
Chorionic villus sampling is complicated by a mosaic result in approximately 1-2% of all cases. Most of these represent confined placental mosaicism.

Early amniocentesis is:

A. Defined as procedures done at 8-10 weeks gestation
B. The procedure of choice for a patient with an elevated risk of Down syndrome in the first trimester
C. Associated with a higher risk of causing miscarriage than traditional amniocentesis
D. The procedure of choice for patients with an elevated maternal serum alpha-fetoprotein

Correct: C

All studies to date have shown the early amniocentesis has a higher loss rate following the procedure than traditional amniocentesis

Counseling prior to prenatal diagnosis in a twin pregnancy should include all of the following statements except:

A. Overall risk of miscarriage is less than that for singleton pregnancy
B. Risk of neural tube defect is higher than in a singleton pregnancy
C. Risk from the procedure is the same in twins as it is for singleton pregnancy
D. Risk for Down syndrome in a woman of age 33 with twins is the same as risk of a 35 year old with a singleton

Correct: A.

The overall risk of miscarriage would be higher because of
the higher background risk in twins.

Pre-implantation genetic diagnosis has a number of potential pitfalls, including all except:

A. Low success rates of implantation for IVF
B. Failure of PCR amplification
C. Crossing over between sister chromatids in polar body biopsy
D. Sperm contamination in polar body biopsy

Correct: D.

Sperm contamination should not occur in a polar body biopsy as this is done prior to fertilization.

When compared to traditional cytogenetics, fluorescence in situ hybridization would
have the greatest benefit in which of the following clinical situations:

A. Father of the pregnancies carrier of a 5:7 translocation
B. Ultrasound evaluation found that the fetus has a Gastroschisis
C. The mother is a known carrier of Fragile X
D. Pregnancy is at increased risk for Down syndrome based on multiple marker screening

Correct: D.

Aneuploidy screening with probes for the common aneuploidy's provides a rapid and accurate diagnosis of Down syndrome.

The most significant risk of chorionic villus sampling is:

A. Fetal injury
B. Maternal infection
C. Clubbed foot
D. Miscarriage

Correct: D

Exact incidence of miscarriage following chorionic villus sampling is not precisely known. Studies comparing amniocentesis and CVS appear to show no increase risk of CVS compared to amniocentesis. However, this is the most common complication following CVS.

Percutaneous umbilical cord sampling would be most useful in which of the following clinical situations:

A. An ultrasound diagnosis indicating that the fetus has absence of both radii
B. A pregnancy at risk for Down syndrome based on a multiple mark screen
C. A fetus at risk for congenital cytomegalovirus infection
D. A fetus found on ultrasound to have an omphalocele

Correct: A.

A fetus found to have absence of radii on ultrasound would be at risk for having the condition known as thrombocytopenia absent radii (TAR). Percutaneous umbilical cord sampling would allow assessment of fetal platelets.

The risk for percutaneous umbilical blood sampling is:

A. Less than that of chorionic villus sampling
B. Lowest when the indication for performing percutaneous umbilical blood sampling is possible fetal infection
C. Greater at later gestational ages
D. Not associated with operator experience

Correct: B.

Maternal infection such as toxoplasmosis and cytomegalovirus are associated with the lowest risk for percutaneous umbilical blood sampling, likely because the fetuses are healthy in most circumstances.

Fetal muscle biopsy is most likely to be indicated in which of the following clinical circumstances: A. Your patient who is 18 weeks pregnant gives a history that her mother died from myotonic dystrophy B. Your patient who is 18 weeks pregnant gives a history that her brother died at 6 months of spinal muscular atrophy C. Your patient who is 18 weeks pregnant gives a history that her brother died of Duchenne muscular dystrophy D. Your patient who is 18 weeks pregnant gives a history that her paternal uncle has Becker muscular dystrophyCorrect: C. In a patient with a history of a brother with Duchenne muscular dystrophy, testing would initially be done on the patient's mother to determine if she has a deletion. In the absence of a deletion, it would not be known whether the patients mother was a carrier, or whether her brother was a new mutation. Therefore, in uteri muscle biopsy could be offered to this patient.Targeted or Level II ultrasound is the procedure of choice in which of the following clinical circumstances: A. A patient with a 1:5 risk of Down syndrome based on a multiple marker screen B. 1st trimester exposure to antidepressants C. A patient whose amniotic fluid AFP is elevated D. A patient who had a chest x-ray performed in the 1st trimesterCorrect: C. An unexplained elevated amniotic fluid AFP is an indicated for targeted ultrasound to determine the possible etiology. That etiology could be a neural tube defect, an omphalocele, or could indicate that this is a falsely positive amniotic fluid AFP.You are referred a patient at 16 weeks gestation with an ultrasound diagnosis of omphalocele. You should recommend all of the following except: A. Amniocentesis B. Fetal echocardiography C. A repeat ultrasound in 3 weeks to confirm the diagnosis D. Referral to Tertiary Center for managementCorrect: C. A repeat ultrasound in 3 weeks should not be performed in this circumstance, as an omphalocele seen at 16 weeks is not physiologic, and represents a true omphalocele.A screening ultrasound at 18 weeks most likely will detect which of the following birth defects: A. Cleft palate B. Spina bifida C. Microcephaly D. AchondroplasiaCorrect: B. Modern ultrasonography is quite good at detecting Spina bifida, not because of actually detecting the lesion itself, but because of the secondary findings in the fetal skull. These so called "lemon sign" and "banana sign" allow the diagnosis to be made in more than 80% of the cases.One method of prenatal diagnosis is to test fetal cells that are circulating within the maternal circulation. All of the following statements regarding fetal cells in the maternal circulation are true except: A. Fetal nucleated red cells are the cell most commonly evaluated B. It is associated with very low false positive rate C. The detection rate for Down syndrome is 50% D. It is recommended that all women undergo a prenatal screening test using fetal cells in the maternal circulationCorrect: D. Fetal cells in maternal circulation has not been shown to be an effective diagnosis or screening tool, and is not recommended for any woman during her pregnancy.Isolation of free fetal DNA from maternal plasma has been shown to be highly accurate in which of the following clinical circumstances: A. Both parents are carriers of known cystic fibrosis genes B. Pregnancy in which the mother is age 40 C. To determine the Rhesus status of the fetus in an Rh sensitized woman D. Mother is a carrier of Fragile XCorrect: C. a mother who Rhesus sensitized is Rh negative. If her fetus is Rh positive it is extremely easy to detect the presence of the gene in her circulation as she does not have this particular gene. This is the most common use of free fetal DNA to date.For a woman who will be age 35 at delivery a genetic counseling session is useful for all of the following reasons except: A. 50% of women above the age of 35 will underestimate their risk for having a child with Down syndrome B. The couple can have a complete discussion of the risks and benefits of both screening test and diagnostic test C. Up to 10% of couples will be found to have a previously unknown genetic or teratogenetic risk factor for the fetus D. Women who do not believe in abortion can be discouraged from having testingCorrect: D. Prenatal testing should be available to any woman regardless of her beliefs about abortion.Beginning in 2007, which of the following indications for prenatal diagnosis was removed from the list of standard indications?: A. Previous child and an autosomal trisomy, such as Down syndrome, trisomy 18 or trisomy 13. B. Patient with an elevated maternal serum alpha fetal protein. C. A patient whose spouse had a neural tube defect. D. Maternal age of 35 years or greater at deliveryCorrect: C. In 2007 the American College of Obstetricians and Gynecologists issued guidelines to state that maternal age should no longer be considered an indication for prenatal diagnosis, and that all women, regardless of age should be offered a screening test such as first trimester screening or multiple marker screening in the second trimester.When counseling a patient regarding chorionic villus sampling, which of the following statements would be appropriate? A. Trans-abdominal chorionic villus sampling is a safer procedure than trans-cervical chorionic villus sampling. B. Chorionic villus sampling is most commonly performed at 9 weeks of gestation. C. Chorionic villus sampling can be safely performed in patients with HIV. D. The risk of chorionic villus sampling is comparable to that of amniocentesis.Correct: D Most recent studies have shown the risk of amniocentesis and CVS to be comparable.Chorionic villus sampling is the procedure of choice as compared to amniocentesis for which of the following conditions: A. Cystic fibrosis B. Fragile X C. Osteogenesis imperfecta, type II D. Duchenne Muscular DystrophyCorrect: C Because the common testing for osteogenesis imperfecta, type II is to assess changes in collagen structure, CVS, and not amniocentesis, is the procedure of choice for prenatal diagnosisYou are asked to provide counseling to a couple whose chorionic villus sampling has indicated mosaicism for trisomy 15. 25% of the cells were found to be trisomic for 15, and 75% have a normal 46, XY. The most appropriate counseling recommendation would be: A. Discuss in detail the clinical features of trisomy 15 mosaicism, and offer the patient the option of pregnancy termination. B. Discuss the clinical implications of trisomy 15 mosaicism, and offer percutaneous umbilical blood sampling to confirm the findings. C. Reassure the patient that trisomy 15 mosaicism is a rare event, and that a detailed ultrasound should be done at 18 weeks. D. Offer an amniocentesis for both chromosome studies and uniparental disomy studies.DYou receive a report from the Cytogenetics laboratory indicating that your patient's CVS sample indicates trisomy 16. All cells analyzed have trisomy 16. Your counseling session for the patient should include which of the following risks: A. There is a very high risk of multiple abnormalities, including mental retardation. B. There is a substantial risk of early onset preeclampsia. C. There is an increased incidence of intrauterine growth restriction. D. B and C only. E. All of the aboveDThe most common risk of 2nd trimester amniocentesis is: A. Rupture of the fetal membranes. B. Fetal injury. C. Miscarriage. D. Clubbed foot.Correct: A - Rupture of the membranes following amniocentesis is the most common risk, but in many cases the membranes will "seal over" and the pregnancy continues.You are asked to see a patient whose 1st trimester screen indicated a risk for Down syndrome of 1:1500, but her maternal serum AFP done in the 2nd trimester was 5:0 MOM. Among the following recommendations, which would be considered the best approach? A. Repeat the maternal serum AFP B. Perform an amniocentesis C. Perform a targeted ultrasound D. Perform percutaneous umbilical blood samplingsCorrect: B Amniocentesis with measurement of amniotic fluid Alpha Fetoprotein and acetylcholinesterase will detect more than 99% of neural tube defects.