Low AFP levels are particularly concerning for which of the following?

Low levels of alpha-fetoprotein (AFP) during pregnancy are particularly concerning for neural tube defects (NTDs). AFP is a protein produced by the fetal liver and is present in the amniotic fluid and the mother’s bloodstream. Normally, AFP levels are evaluated during the second trimester as part of routine prenatal screening.

When NTDs, such as spina bifida or anencephaly, occur, they can lead to a leak of AFP into the amniotic fluid, but in cases where the defect is significant, blood levels of AFP may not appropriately elevate. This is due to the fact that the fetal tissue producing AFP is compromised. Consequently, low AFP levels can indicate that there may be an increased risk of neural tube defects, which is why this finding is particularly concerning and warrants further evaluation through diagnostic testing like ultrasound or amniocentesis.

In contrast, while low AFP levels may be associated with other conditions such as fetal growth restriction, gestational diabetes, and preterm labor, these associations are not as well established as with neural tube defects. Therefore, the primary concern with low AFP levels focuses on the risk for neural tube defects, highlighting the importance of this marker in prenatal screening protocols.