MSAFP stands for maternal serum alpha-fetoprotein. What is it?

• A. A protein found in fetal plasma that crosses into maternal circulation.
• B. A hormone produced by the placenta.
• C. An enzyme produced by fetal liver.
• D. A maternal antibody marker against fetal antigens.

Answer: (A)

MSAFP is a protein produced by the fetus (mainly by the liver and yolk sac) that crosses into the maternal bloodstream, allowing its level to be measured in maternal serum during mid-pregnancy. This fetal protein appears in mom’s blood and is used as a screening marker to assess risk for neural tube defects and ventral wall defects, as well as to help identify dating or multiple-gestation issues. It is not a hormone produced by the placenta, not an enzyme from the fetal liver, and not a maternal antibody marker.