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

OBJECTIVE

Unexplained elevations of maternal serum alpha-fetoprotein levels in the second trimester of pregnancy are associated with adverse pregnancy outcomes, including intrauterine growth retardation, preterm delivery, preeclampsia, and abruptio placentae. In addition, elevations of maternal serum alpha-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 alpha-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 of 201 women with an elevated maternal serum alpha-fetoprotein (> or = 2.0 multiples of the median) and a second-trimester ultrasonographic evaluation at Swedish Hospital Medical Center and 211 women with normal maternal serum alpha-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 alpha-fetoprotein was associated with the following adverse pregnancy outcomes: 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 alpha-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 alpha-fetoprotein and placental abnormalities detected 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 alpha-fetoprotein.