Prenatal Genetics & Reproductive Options Flashcards

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

Answer: Trisomy 21 (Down syndrome)

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

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

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

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

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

Answer: 1 in 100 to 1 in 200

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

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

Answer: 10–13 weeks

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

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:

Answer: 1 in 385

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

Preimplantation genetic testing for aneuploidy (PGT-A) is used to:

Answer: Screen embryos created through IVF for chromosomal abnormalities before transfer

PGT-A screens IVF embryos for aneuploidy prior to uterine transfer to improve implantation success and reduce miscarriage risk.