Objective: To estimate the risk of placenta-mediated complications in women in their third delivery according to their obstetric history in the first and second deliveries.
Methods: A retrospective cohort study of all women with singleton pregnancies who delivered their first three consecutive deliveries in a single medical center over a 20-year period (1994-2013). The risk of placenta-mediated complications in the third delivery, that is, hypertensive disorders such as preeclampsia or gestational hypertension, placental abruption, and small for gestational age (SGA less than the 10th percentile), was assessed according to the presence or absence of complications in previous deliveries. Pregnancies complicated by multiple gestations or fetal anomalies were excluded.
Results: Of the 121,728 deliveries during the study period, 4,472 women (13,416 deliveries [11.0%]) met inclusion criteria. The rate of placenta-mediated complications in the third delivery was 5.9% (n=264). The most prevalent placenta-mediated complication was SGA. The risk of each placenta-mediated complication was greater the higher the incidence of placenta-mediated complications in prior pregnancies. In multivariate analysis, that risk was significantly associated with the number and order of complications in previous deliveries in a dose-dependent pattern: with no complications in either their first or second deliveries as a reference (n=3,650), the adjusted odds ratio (and 95% confidence intervals) was 4.35 (3.03-6.24) for complications in the first delivery but not the second delivery (n=532); 6.41 (3.95-10.38) for complications in the second delivery but not the first delivery (n=179); and 8.28 (4.72-14.58) for complications in both first and second deliveries (n=111), (P<.001).
Conclusion: The number and order of previous placenta-mediated complications in the first two deliveries are major risk factors for recurrence in the third delivery. Previous SGA was the strongest risk factor for recurrence of SGA and other placenta-mediated complications.