Purpose
To assess incidence and risk factors for postpartum hemorrhage (PPH) and identify women at high risk of recurrence in the subsequent pregnancy.

Methods
This register-based study includes data on women from the Capital Region of Denmark with two consecutive deliveries recorded in the Copenhagen Obstetric Database from 2007 to 2020. PPH, defined as a blood loss of 1000 mL or more within 24 h after delivery, was the primary outcome measure. We calculated incidence and recurrence rate of PPH and assessed possible risk factors at index and subsequent deliveries.

Results
We included 44,800 women with 95,673 deliveries. The overall incidence of PPH was 6.3%. Women with previous PPH had a 3.5-fold increased risk of PPH in a subsequent delivery compared to unaffected women (19.1 vs. 5.4%; OR 4.1; 95% CI 3.7–4.5). Major risk factors for recurrence were PPH in combination with blood transfusion or manual removal of placenta at the index delivery. Labor induction in subsequent pregnancy increased the risk of recurrent PPH compared to spontaneous onset (OR 1.5; 95% CI 1.2–1.9), while planned caesarean section reduced the risk, compared to planned vaginal delivery (OR 0.6; 95% CI 0.4–0.7).

Conclusion
Previous PPH increases the risk of PPH in subsequent pregnancy 3.5-fold. The risk of recurrent PPH increases with labor induction and decreases with planned caesarean section in the subsequent pregnancy. To prevent recurrent PPH, personalized counseling based on risk factors, relevant labor history and maternal preferences is suggested.