Prospective evaluation of placental abruption in nulliparous women

Introduction: Because most data on placental abruption are derived from retrospective studies, multiple sources of bias may have affected the results. Thus, we aimed to characterize risk factors and outcomes for placental abruption in a large prospective cohort of nulliparous women.

Methods: This was a secondary analysis of women enrolled in the Nulliparous Pregnancy Outcomes Study Monitoring-to-be (nuMom2b) study, a prospective observational cohort. Participants were recruited in their first trimester of pregnancy from 8 sites and had 4 study visits, including at delivery. Placental abruption was defined by confirmed clinical criteria. The primary analysis was restricted to abruption identified antepartum and intrapartum. As a secondary analysis, we examined antepartum and intrapartum abruptions separately. We compared risk factors (maternal demographic and clinical characteristics) and outcomes in women with and without placental abruption using univariable and multivariable analyses as appropriate.

Results: 9450 women were included in the primary analysis. Abruption was identified in 0.66% (n = 62), of which 35 (56%) were antepartum and 27 (44%) intrapartum. For women with abruption, the mean gestational age at delivery was 35.6 ± 4.4 weeks and 38.8 ± 2.2 weeks for women without abruption. Gravidity was associated with abruption (OR 3.1, 95% CI: 1.6-6.0). In univariate analysis, abruption was associated with cesarean delivery (OR 3.7, 95% CI: 2.2-6.0), blood transfusion (OR 3.8, 95% CI: 1.4-10.7), PPROM (OR 9.0, 95% CI: 5.4-15.1), preterm birth (OR 8.5, 95% CI: 5.1-14.2), SGA (OR 4.0, 95% CI: 2.3-6.95), RDS (OR 5.5, 95% CI: 2.6-11.2), IVH 20.2 (OR 20.2, 95% CI: 5.9-68.8) and ROP (OR 12.2, 95% CI: 2.8-52.6). However, after adjustment for confounders including gestational age, abruption was only associated with increased odds of cesarean delivery and blood transfusion. Results were similar when restricted to antepartum and intrapartum abruptions.

Conclusion: Abruption was identified in <1% of nulliparous women. However, few maternal risk factors were identified. Neonatal morbidities were associated with an abruption and were primarily driven by gestational age due to preterm birth.