Second-trimester maternal serum alpha-fetoprotein and risk of adverse pregnancy outcome(1)

To determine the risk of adverse pregnancy outcome by maternal serum alpha-fetoprotein (MSAFP) level.

We followed 77,149 pregnant women and their infants from MSAFP screening in the 15th to 20th week of gestation until 1 year after birth. Information on pregnancy outcome was obtained from national registries. The relative risks (RRs) and 95% confidence intervals (CIs) for adverse pregnancy outcome were estimated according to the level of MSAFP, with adjustment for confounders.

A total of 638 pregnancies resulted in spontaneous abortion, 289 in stillbirth, and 437 in infant death. Compared with women with MSAFP levels at 0.75-1.24 multiples of the median (MoM), those with MSAFP levels greater than or equal to 2.5 MoM had an increased risk of spontaneous abortion (RR 12.5; 95% CI 9.7, 16.1), preterm birth (RR 4.8; 95% CI 4.1, 5.5), small for gestational age (RR 2.8; 95% CI 2.4, 3.2), low birth weight (RR 5.8; 95% CI 5.0, 6.6), and infant death (RR 1.9; 95% CI 1.2, 2.8). Women with MSAFP levels below 0.25 MoM had an increased risk of spontaneous abortion (RR 15.1; 95% CI 9.3, 24.8), preterm birth (RR 2.2; 95% CI 1.3, 3.8), and stillbirth (RR 4.0; 95% CI 1.0, 16.0); those with levels less than 0.5 MoM had an increased risk of infant death (RR 1.9; 95% CI 1.2, 3.0). The increased risk of infant death remained after the subtraction of recognized conditions associated with extreme MSAFP values.

Pregnant women with extreme MSAFP values in the second trimester have an increased risk of fetal and infant deaths. Obstet Gynecol 2001;97:277-82.