Objective: To describe the association between pregnancy associated plasma protein A (PAPP-A), alpha-fetoprotein (AFP) and adverse perinatal outcome.
Methods: We conducted a multicenter prospective cohort study of 8,483 women attending for prenatal care in southern Scotland between 1998 and 2000. The risk of delivering a small for gestational age infant, delivering preterm, and stillbirth were related to maternal serum levels of PAPP-A and AFP.
Results: Women with a low PAPP-A were not more likely to have elevated levels of AFP. Compared with women with a normal PAPP-A and a normal AFP, the odds ratio for delivering a small for gestational age infant for women with a high AFP was 0.9 (95% confidence interval [CI] 0.5-1.6), for women with a low PAPP-A was 2.8 (95% CI 2.0-4.0), and for women with both a high AFP and a low PAPP-A was 8.5 (95% CI 3.6-20.0). The odds ratio for delivering preterm for women with a high AFP was 1.8 (95% CI 1.3-2.7), for women with a low PAPP-A was 1.9 (95% CI 1.3-2.7), and for women with both a low PAPP-A and a high AFP was 9.9 (95% CI 4.4-22.0). These interactions were statistically significant for both outcomes (P = .03 and .04, respectively). There was a nonsignificant trend toward a similar interaction in relation to stillbirth risk. Of the women with the combination of a low PAPP-A and high AFP, 32.1% (95% CI 15.9-52.4) delivered a low birth weight infant.
Conclusion: Low maternal serum levels of PAPP-A between 10 and 14 weeks and high levels of AFP between 15 and 21 weeks gestation are synergistically associated with adverse perinatal outcome.
Level of evidence: II-2.