Which first-trimester screening statement best assesses fetal aneuploidy risk?

• A. Quad screen offered in the first trimester
• B. Nuchal translucency ultrasound with maternal serum markers PAPP-A and free β-hCG, with consideration of noninvasive prenatal testing (NIPT)
• C. Amniocentesis is the primary first-trimester screen
• D. Anatomy scan in the first trimester

Answer: (B)

Assessing fetal aneuploidy risk in the first trimester relies on combining ultrasound assessment of nuchal translucency with maternal serum markers (PAPP-A and free β-hCG), and often extending with noninvasive prenatal testing. Nuchal translucency measures the fluid at the back of the fetal neck; increased NT thickness is associated with higher risk of chromosomal abnormalities. The serum markers reflect placental function: low PAPP-A and altered free β-hCG levels contribute to a pattern that, when paired with NT measurement, helps estimate risk for trisomies such as 21, 18, and 13. Adding NIPT—analyzing fetal cell-free DNA in maternal blood—can further stratify risk with high sensitivity and specificity without invasive testing.

The other options are not best for first-trimester screening: a quad screen uses four markers in the second trimester, not the first; amniocentesis is a diagnostic test (invasive) usually performed after mid-pregnancy or when risk is indicated; the anatomy scan is a structural evaluation conducted later, typically around 18–22 weeks, not in the first trimester.