Obstetric Nurse Prenatal Care and Patient Education Flashcards

Cell-free DNA (cfDNA) screening is most sensitive and specific for detecting which chromosomal condition?

Answer: Trisomy 21 (Down syndrome)

cfDNA screening has the highest sensitivity (>99%) and specificity for detecting trisomy 21 (Down syndrome) compared to other chromosomal conditions.

Amniocentesis for chromosomal analysis is typically performed at which gestational age?

Answer: 15–20 weeks

Amniocentesis is generally performed between 15–20 weeks when sufficient amniotic fluid is present and procedural risk is minimized.

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

Answer: 10–13 weeks

CVS is performed in the first trimester at 10–13 weeks, allowing earlier chromosomal diagnosis than amniocentesis.

A patient with a positive NIPT result for trisomy 18 should be counseled that the next step is:

Answer: Confirmatory diagnostic testing such as amniocentesis or CVS should be offered

NIPT is a screening test, not diagnostic; a positive result must be confirmed with amniocentesis or CVS before any major clinical decisions are made.

Which maternal serum marker is ELEVATED in open neural tube defects on the second-trimester quad screen?

Answer: Alpha-fetoprotein (AFP)

AFP leaks from the fetal cerebrospinal fluid into the amniotic fluid and then into maternal serum when the neural tube is open, causing an elevated MSAFP.

A patient at 18 weeks has an anatomy ultrasound showing echogenic bowel. The nurse knows this finding is considered:

Answer: A soft marker that may be associated with trisomy 21, cystic fibrosis, or IUGR

Echogenic bowel is a soft ultrasound marker associated with several conditions including Down syndrome, cystic fibrosis, swallowed blood, and growth restriction, warranting further evaluation.