Maternal Serum Markers of Fetal Abnormalities: Progress in Prenatal Screening.

Second-trimester screening of a pregnant woman's serum for markers of such congenital abnormalities as fetal trisomy 21 (Down syndrome) and neural tube defects has become an important part of antenatal care. The protocol most commonly used is the triple marker screen, which measures serum levels of alpha-fetoprotein (AFP), unconjugated estriol (uE3), and beta-human chorionic gonadotropin (beta-hCG). The results of these tests are used to derive a value known as a multiple of the median (MoM). An algorithm that combines maternal age with MoMs can be used to calculate the risk for such chromosomal disorders as trisomy 21 and 18. AFP alone--corrected for weight, race, insulin-dependent diabetes, and multiple pregnancy--can be used to predict the risk of fetal neural tube defect. Prenatal screening is best performed within an integrated program providing biochemical testing in conjunction with knowledgeable experienced counselors, expert ultrasonographers, and physicians with special expertise in maternal fetal medicine and neonatal care. Prenatal screening provides parents with the information they need to make informed pregnancy decisions and, if necessary, organize support and resources essential to the care of an infant with special needs.