Maternal Markers and Complications of Pregnancy

In recent years maternal serum screening in the second trimester of pregnancy has become a routine part of prenatal care in the United States and other industrialized nations. Maternal serum screening is designed to identify women whose fetuses are at increased risk for congenital anomalies, including neural-tube defects, other open fetal abnormalities, trisomy 21, and trisomy 18. Most commonly, alpha-fetoprotein, unconjugated estriol, and either intact human chorionic gonadotropin or its β subunit are measured in serum. Absolute values for these analytes are converted to multiples of the normal median for each gestational age and together used to modify the mother's . . .