Placental abruption: Incidence and risk of recurrence in subsequent pregnancies.

Aim: To estimate the incidence of abruption in first births and recurrence in the subsequent birth in patients of a large US-based integrated health care system.

Methods: Retrospective population-based cohort study of patients with first two consecutive singleton births using data from the Kaiser-Permanente South California health care system who delivered over a period of 30 years (1991-2021), using longitudinally linked electronic health records. ICD-9/ICD-10 codes "641.20" and "O45.x" identified placental abruption. We calculated the incidence and rates of abruption in first and second pregnancies. We used logistic regression to estimate the adjusted odds ratios (aOR) for abruption in second pregnancies in patients with and without abruptions in their first pregnancies.

Results: Of the 126 264 patients with first two consecutive singleton births over the period, 805 had abruptions in their first births, and 861 in their second births. Rates of abruption in first and second births were 0.63% and 0.68%, respectively. Twenty-seven patients had abruptions in both first and second births. Rates of abruption in the second birth among individuals with and without previous placental abruption were 3.35% and 0.66%, respectively, giving an approximately five-fold increased odds of abruption in a second pregnancy in individuals who had abruption in their first birth when compared with those who did not have placental abruption in their first birth (aOR: 4.95, 95% confidence interval: 3.35-7.31, p < 0.00001). Interpregnancy interval had no statistically significant association with recurrence.

Conclusion: Abruption in a first birth is associated with an approximately five-fold increased odds of abruption in a second birth.