Unexplained elevations of maternal serum alpha-fetoprotein.

Alpha-fetoprotein (AFP) is a commonly used prenatal screening test for congenital anomalies. However, when anomalies are excluded after high resolution ultrasound and/or amniocentesis, an elevated maternal serum AFP (MSAFP) has been found to be associated with a 2- to 4-fold increase in low birthweight resulting from both preterm delivery and intrauterine growth retardation. Unexplained MSAFP elevations are also associated with up to 10-fold increase of placental abruption and a 10-fold increase in perinatal mortality. Results from studies of over 225,000 screened pregnancies indicate that 20 and 38 per cent of women with an unexplained MSAFP elevation may have an adverse pregnancy outcome. Twin gestations with MSAFP elevations greater than four multiples of the median are associated with similar constellations of pregnancy complications. Maternal serum AFP elevations in women with pregnancy complications are most likely the result of a leak of AFP across the placenta. Optimum management of women with unexplained elevations has not yet been established; however, evaluation of fetal growth throughout gestation is important in these patients.