Elevated AFP in maternal serum screening is most commonly associated with which condition?

• A. Neural tube defects
• B. Trisomy 21
• C. Preeclampsia
• D. Ectopic pregnancy

Answer: (A)

Elevated maternal serum AFP points to open neural tube defects in the fetus. AFP is produced by the fetal liver and yolk sac and normally appears in maternal blood at low levels; when the neural tube fails to close properly, AFP leaks into the amniotic fluid and then into the mother's circulation, raising the measured AFP. Classic conditions linked to this pattern are open spina bifida and anencephaly. By contrast, Down syndrome is typically associated with lower AFP levels, while preeclampsia or ectopic pregnancy don’t produce the same AFP elevation pattern. Keep in mind that dating errors or multiple gestations can affect values, but the strongest link in screening is elevated AFP with neural tube defects.