Elevated maternal serum α-fetoprotein levels and midtrimester placental abnormalities in relation to subsequent adverse pregnancy outcomes

OBJECTIVE: Unexplained elevations of maternal serum α-fetoprotein levels in the second trimester ofpregnancy are associated with adverse pregnancy outcomes, including intrauterine growth retardation, preterm delivery, preeclampsia, and abruptio placentae. In addition, elevations of maternal serum α-fetoprotein have been associated with placental lesions detected during second-trimester ultrasonographic evaluations. We examined the relationship between adverse pregnancy outcomes and unexplained elevations of maternal serum α-fetoprotein and placental abnormalities in the second trimester of pregnancy. STUDY DESIGN: During the period from January 1989 to March 1991 we conducted a cohort study of201 women with an elevated maternal serum α-fetoprotein (≥2.0 multiples of the median) and a second-trimester ultrasonographic evaluation at Swedish Hospital Medical Center and 211 women with normal maternal serum α-fetoprotein levels who had also undergone ultrasonographic evaluation at the same institution. All women in this investigation had singleton pregnancies without fetal anomalies. RESULTS: Elevated maternal serum α-fetoprotein was associated with the following adverse pregnancyoutcomes: low birth weight (adjusted risk ratio 3.7), preterm delivery (adjusted risk ratio 3.6), intrauterine growth retardation (adjusted risk ratio 4.0), preeclampsia (adjusted risk ratio 3.8) and abruptio placentae (adjusted risk ratio 4.8). Placental abnormalities detected during second-trimester ultrasonographic evaluations were also associated with adverse pregnancy outcomes: low birth weight (adjusted risk ratio 2.0), preterm delivery (adjusted risk ratio 2.3), intrauterine growth retardation (adjusted risk ratio 1.4), and abruptio placentae (adjusted risk ratio 9.0). A joint positive history of second-trimester elevations of maternal serum α-fetoprotein and placental abnormalities was more strongly associated with the following adverse infant outcomes: low birth weight (adjusted risk ratio 6.9), preterm delivery (adjusted risk ratio 5.6), and intrauterine growth retardation (adjusted risk ratio 5.3). CONCLUSIONS: Unexplained elevated levels of maternal serum α-fetoprotein and placental abnormalitiesdetected in the second trimester of pregnancy are associated with particularly poor pregnancy outcome. Careful examination for placental abnormalities should be part of the evaluation of elevated maternal serum α-fetoprotein. (Am J Obstet Gynecol 1992;167:1032–7.)