A 24-year-old primigravida at 12 weeks gestation attends her first antenatal visit. She has no significant past medical history. Which of the following maternal serum markers is characteristically ELEVATED in Down syndrome (trisomy 21) when measured at 15–20 weeks gestation?
- A Alpha-fetoprotein (AFP)
- B Unconjugated estriol (uE3)
- C Human chorionic gonadotropin (hCG) ✓
- D Inhibin A
Correct answer: C. Human chorionic gonadotropin (hCG)
Explanation
In the second-trimester quadruple screen for trisomy 21, hCG is characteristically elevated (~2.0 MoM), while AFP and unconjugated estriol are both decreased. Inhibin A is also elevated in Down syndrome and its addition to AFP, uE3, and hCG constitutes the quad screen. Elevated AFP is a marker for open neural tube defects, not Down syndrome.
Reference: Williams Obstetrics, 26th ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
Written and medically reviewed by the StethoPrep medical team.