If a baby has a neural tube defect, what is the expected level of a-FP in the quad screen?

In the context of a neural tube defect, the expected level of alpha-fetoprotein (a-FP) in the quad screen is elevated. Neural tube defects, such as spina bifida and anencephaly, allow for an abnormal increase of a-FP into the maternal circulation. This is because a-FP is produced by the fetal liver, and if there is a defect that permits fetal proteins to enter the amniotic fluid and subsequently the maternal bloodstream, the levels of a-FP will be higher than normal.

In cases of neural tube defects, the increased levels of a-FP can be significant; therefore, clinicians often use the quad screen test to help identify pregnancies that may be at risk for such anomalies. Elevated a-FP is a key indicator that prompts further diagnostic evaluation, typically through ultrasound and possibly amniocentesis, to confirm or rule out a neural tube defect.

Understanding the significance of a-FP levels in screening tests is critical for proper prenatal care and management. In contrast, other outcomes where a-FP levels may be normal or low would point towards a lower risk for these types of defects.