Identifying risk factors for placental abruption in subsequent pregnancy without a history of placental abruption

Objective: To identify first pregnancy risk factors for placental abruption in subsequent pregnancy. Methods: In a population-based nested case–control study, cases were defined as women with placental abruption in their second pregnancy, and controls as women without abruption. A total of 43 328 women were included in the study, 0.4% (n = 186) of second pregnancies had placental abruption. Multivariable logistic models were used to study the association between first pregnancy complications and placental abruption in subsequent pregnancy. Results: Having either small for gestational age, preterm delivery, pre-eclampsia or cesarean delivery during first pregnancy were independently associated with increased risk for placental abruption, and the risk was higher with any additional complication (age adjusted odds ratio [aOR] 2.00, 95% confidence interval [CI] 1.46–2.74; aOR 3.61, 95% CI 2.23–5.86; and aOR 3.86, 95% CI 1.56–9.56, for one, two, and three or more complications, respectively). Conclusion: First pregnancy may serve as a window of opportunity to identify women at risk for future placental abruption.