CGC Prenatal Genetics & Reproductive Options 2 — Questions and Answers
Question 1: Carrier screening for spinal muscular atrophy (SMA) is recommended for:
- Only Ashkenazi Jewish individuals
- All individuals of reproductive age regardless of ethnicity (Correct answer)
- Individuals with a family history of SMA only
- Women over 35 years of age
Correct answer: All individuals of reproductive age regardless of ethnicity
Current ACOG guidelines recommend expanded carrier screening, including SMA, for all individuals of reproductive age due to pan-ethnic prevalence.
Question 2: When both members of a couple are carriers for an autosomal recessive condition, the recurrence risk with each pregnancy is:
- 100%
- 75%
- 50%
- 25% (Correct answer)
Correct answer: 25%
When both parents are carriers for an autosomal recessive condition, each pregnancy has a 25% chance of being affected.
Question 3: A nuchal translucency (NT) measurement of ≥3.5 mm at 11–14 weeks is associated with increased risk for:
- Neural tube defects only
- Chromosomal abnormalities and structural defects including cardiac anomalies (Correct answer)
- Neural tube defects and Down syndrome only
- Premature labor exclusively
Correct answer: Chromosomal abnormalities and structural defects including cardiac anomalies
An increased NT is associated with a broad spectrum of chromosomal aneuploidies, structural anomalies, and genetic syndromes.
Question 4: Preimplantation genetic testing for monogenic conditions (PGT-M) requires which INITIAL step?
- Confirming the couple's carrier status via blood draw
- Identifying the specific familial pathogenic variant through proband testing (Correct answer)
- Completing two rounds of IVF before analysis
- Submitting a referral to a reproductive endocrinologist
Correct answer: Identifying the specific familial pathogenic variant through proband testing
PGT-M requires knowledge of the exact familial variant so the laboratory can design a specific probe or analysis strategy for the embryo.
Question 5: A pregnant patient is found to have a fetal ultrasound showing an isolated echogenic bowel. This finding is associated with increased risk for which genetic condition?
- Trisomy 13
- Cystic fibrosis (Correct answer)
- Turner syndrome
- Fragile X syndrome
Correct answer: Cystic fibrosis
Echogenic bowel is a soft marker associated with cystic fibrosis, as swallowed meconium in an affected fetus can appear echogenic on ultrasound.
Question 6: When counseling a couple for whom one partner is a carrier of an X-linked recessive condition, which reproductive outcome is CORRECT?
- All sons will be affected
- 50% of sons will be affected and 50% of daughters will be carriers (Correct answer)
- All daughters will be affected
- 25% of all children will be affected
Correct answer: 50% of sons will be affected and 50% of daughters will be carriers
For X-linked recessive conditions, carrier mothers pass the variant to 50% of sons (who are affected) and 50% of daughters (who are carriers).
CGC Prenatal Genetics & Reproductive Options 2
Carrier screening for spinal muscular atrophy (SMA) is recommended for: