Extreme values of maternal serum analytes in second trimester screening: looking beyond trisomy and NTD's.

Second trimester maternal serum screening can identify high risk pregnancies and fetuses at risk for birth defects (in addition to those in the standard interpretation). The purpose of this study was to quantify such risks to improve counseling. We compared outcomes of 692 pregnancies that had abnormal levels of at least one analyte with a cohort of 713 pregnancies with normal analytes. Increased risks include: demise with high AFP and low uE3; intrauterine growth restriction with high AFP, high and low hCG, and low uE3; placental abnormalities with high AFP; fetal stress with high AFP and high hCG. Birth defects are increased with high AFP, high hCG, and low hCG. When two or more analytes are abnormal, 46% have a poor outcome. Abnormal levels of maternal serum analytes provide information in addition to the risks for neural tube defects, Down syndrome, and trisomy 18. This information is important for counseling and pregnancy management.