THE ASSOCIATION BETWEEN MATERNAL SERUM ALPHA-FETOPROTEIN AND PRETERM BIRTH, SMALL-FOR-GESTATIONAL-AGE INFANTS, PREECLAMPSIA, AND PLACENTAL COMPLICATIONS

Objective: To determine whether high levels of serum alpha-fetoprotein (AFP) predict increased risk of adverse pregnancy outcomes, including preterm birth (before 37 weeks), preterm birth occurring at or before 28 weeks, small for gestational age (SGA) infant, preeclampsia, and p lacental abnormalities, and to determine whether low levels of serum A FP predict increased or decreased risk of these outcomes. Methods: Usi ng the mother's first name, last name, and zip code, we linked the rec ords of 51,008 women who participated in the California Alpha-Fetoprot ein Screening Program between June 15, 1986, and October 31, 1987, wit h California birth certificates for singleton infants born in 1987. Th e accuracy of the data linkage was confirmed by manually examining com plete names, mother's ethnicity, and mother's age for a sample of 500 of the mother-infant linkages. Blood samples were obtained at 15-19 we eks. Results: A strong gradient of increasing risk of preterm birth wi th increasing levels of serum ARP was observed (test for trend, P < .0 1). Among women with high levels of serum AFP (at least 2.5 multiples of the median [MoM]), 24.3% had preterm births, compared with 3.8% of women with low levels of serum AFP (0.81 MoM or less), odds ratio 8.7, 95% confidence interval 7.1-10.7). This gradient persisted when prete rm infants of 28 weeks or less were examined separately. Similar gradi ents were observed for the risk of preeclampsia and placental abnormal ities. There was a weaker U-shaped relation between serum AFP level an d the risk of an SGA infant. Conclusion: Low levels of second-trimeste r maternal serum AFP are associated with a very low risk of preterm bi rth, preeclampsia, and placental complications. High levels of serum A FP are strongly associated with preterm birth, preeclampsia, and place ntal abnormalities. There is a modest association between AFP levels ( both low and high) and SGA birth.