MSAFP
Also written as: MSAFP — maternal serum alpha-fetoprotein
Maternal serum alpha-fetoprotein; second-trimester screening test for neural tube defects and chromosomal abnormalities.
Full Definition
Maternal serum alpha-fetoprotein (MSAFP) is a glycoprotein produced by the fetal liver and yolk sac that crosses into maternal circulation through the placenta. Measured between 15-22 weeks of pregnancy, MSAFP levels serve as a screening tool for fetal anomalies. Elevated levels (typically >2.5 multiples of the median) suggest neural tube defects, abdominal wall defects, or multiple gestations. Decreased levels may indicate chromosomal abnormalities such as Down syndrome or trisomy 18. MSAFP is often part of multiple marker screening (triple or quad screen) that includes human chorionic gonadotropin, unconjugated estriol, and inhibin A. Abnormal results require further evaluation with detailed ultrasound and possible amniocentesis.
Usage
Usage note: Distinguish from amniotic fluid AFP; always specify units (MoM) when reporting levels.
In Context
- "The MSAFP level of 4.2 MoM prompted immediate detailed ultrasound examination to rule out neural tube defects." — Prenatal screening report
- "Low MSAFP in combination with elevated hCG suggested increased risk for trisomy 21, warranting genetic counseling." — Maternal fetal medicine consultation