ABSTRACT
Screening tests to identify women at risk for fetal aneuploidy and fetal structural abnormalities are routinely offered to all women during pregnancy. A number of screening strategies are currently available, which utilize both biochemical analysis and ultrasonography to achieve high detection rates and determine whether further diagnostic testing is needed. Most second-trimester serum marker screening is now performed in conjunction with first trimester-combined screening protocols that utilize either an integrated, stepwise, or contingent approach. Whether integrated with first-trimester serum marker testing or used in isolation for women who defer first-trimester screening or do seek prenatal care until after 13 weeks of gestation, second-trimester serum marker screening remains a valuable tool in prenatal management. Maternal serum alpha-fetoprotein was the first maternal serum analyte utilized to detect fetal abnormalities, specifically, open neural tube and abdominal wall defects in cases of elevated MSAFP.
