CGC Prenatal Genetics & Reproductive Options

Question 1

Cell-free DNA (cfDNA) screening in pregnancy MOST accurately screens for which condition?

Accepted Answer

Trisomy 21 (Down syndrome)

Answer

cfDNA screening has the highest sensitivity and specificity for trisomy 21 among common chromosomal aneuploidies.

Question 2

A patient with a positive cfDNA result for trisomy 18 should be counseled that:

Accepted Answer

Diagnostic confirmation via amniocentesis or CVS is recommended before clinical decisions are made

Answer

cfDNA is a screening test, not diagnostic; a positive result requires invasive diagnostic confirmation before clinical management decisions.

Question 3

The procedure-related pregnancy loss risk associated with amniocentesis is approximately:

Accepted Answer

1 in 100 to 1 in 200

Answer

Contemporary studies estimate the procedure-related loss rate for amniocentesis at approximately 1 in 100 to 1 in 200, though older estimates were higher.

Question 4

Chorionic villus sampling (CVS) is typically performed at which gestational age?

Accepted Answer

10–13 weeks

Answer

CVS is performed in the first trimester between 10 and 13 weeks, providing earlier diagnostic results compared to amniocentesis.

Question 5

A patient of advanced maternal age asks about the risk of chromosomal abnormalities. The counselor explains that the baseline risk for trisomy 21 at age 35 is approximately:

Accepted Answer

1 in 385

Answer

At age 35, the risk for trisomy 21 is approximately 1 in 385, which has historically defined the threshold for discussing invasive prenatal diagnosis.

CGC - Certified Genetic Counselor Practice Test

CGC - Certified Genetic Counselor Practice Test

CGC Prenatal Genetics & Reproductive Options