Maternal plasma alpha-fetoprotein and low birthweight: a prospective study throughout pregnancy

Maternal plasma alpha-fetoprotein (AFP) was measured serially between 15 weeks gestation and term in 520 patients. Thirty-seven of these women were delivered of normal singleton infants with birthweights less than 2.5 kg. The median plasma AFP values in this group of women were highest between 15 and 20 weeks gestation and then declined steadily towards term. It is concluded that the use of maternal plasma or serum AFP in the early detection of low birthweight babies is optimal in the period most suitable for screening for fetal neural tube defects.