Maternal serum α-fetoprotein at 11-13 weeks' gestation in spontaneous early preterm delivery.

OBJECTIVE To examine the potential value of maternal serum level of α-fetoprotein (AFP) in the first trimester of pregnancy in the prediction of spontaneous early preterm delivery. METHODS Maternal serum concentration of AFP at 11-13 weeks' gestation was measured in a case-control study of singleton pregnancies delivering phenotypically normal neonates, including 33 cases with spontaneous delivery before 34 weeks and 99 matched controls delivering after 37 weeks. The median multiple of the median (MoM) serum AFP in the two outcome groups was compared and the bivariate gaussian distributions were simulated in a previously described screened population of 33,370 pregnancies to estimate the performance of screening for early delivery by a combination of maternal characteristics and obstetric history with serum AFP. RESULTS In the preterm delivery group compared to the term delivery group, the median serum AFP MoM was higher (1.33 vs. 0.97, p = 0.006). The estimated detection rate of preterm delivery, at a false-positive rate of 10%, from maternal characteristics and obstetric history was 27.5% and this increased to 36.0% with the addition of serum AFP. CONCLUSIONS Measurement of serum AFP at 11-13 weeks improves the prediction of early preterm delivery provided by maternal characteristics and obstetric history.