Objective: To examine whether using selective serotonin reuptake inhibitors and selective serotonin-norepinephrine reuptake inhibitors in pregnancy is associated with an increased risk of postpartum hemorrhage.
Methods: We conducted a population-based cohort study including 225,973 women with 322,224 pregnancies in British Columbia, Canada, between 2002 and 2011. Women were categorized according to whether they had late-pregnancy exposure (at least 15 of the last 30 days of pregnancy), midpregnancy exposure (in the last 5 months of pregnancy but not the final 30 days), or no exposure. Postpartum hemorrhage was identified using International Classification of Diseases (9th and 10th Revisions) codes in data on all hospitalizations.
Results: We found an increased risk of postpartum hemorrhage associated with exposure to an serotonin-norepinephrine reuptake inhibitor in the final month of pregnancy after adjustment for potential confounders (n=1,390; adjusted odds ratio [OR] 1.76, 95% confidence interval [CI] 1.47-2.11, respectively) corresponding to 4.1 (95% CI 2.4-5.7) additional cases of postpartum hemorrhage per 100 people treated. There was no significant relationship between selective serotonin reuptake inhibitor use in the final month of pregnancy and postpartum hemorrhage (n=6,637; adjusted OR 1.09, 95% CI 0.98-1.21), except when confining the cohort to women with complete body mass index (BMI) information (n=235,031 [73%]) and controlling for BMI (adjusted OR 1.14, 95% CI 1.01-1.28) or when controlling for variables that are possibly on the causal pathway (adjusted OR 1.13, 95% CI 1.02-1.26). Midpregnancy exposure to a serotonin-norepinephrine reuptake inhibitor (n=242) or a selective serotonin reuptake inhibitor (n=1,507) was not associated with an increased postpartum hemorrhage risk.
Conclusion: Serotonin-norepinephrine reuptake inhibitor exposure in late pregnancy was associated with a 1.6- to 1.9-fold increased risk of postpartum hemorrhage.