Outpatient calcium-channel blockers and the risk of postpartum haemorrhage: a cohort study

ObjectiveTo determine whether outpatient exposure to calcium-channel blockers (CCBs) at the time of delivery is associated with an increased risk for postpartum haemorrhage (PPH). DesignCohort study. SettingUnited States of America. Population or sampleMedicaid beneficiaries. MethodsWe identified a cohort of 9750 patients with outpatient prescriptions for CCBs, methyldopa, or labetalol for pre-existing or gestational hypertension whose days of supply overlapped with delivery; 1226 were exposed to CCBs. The risk of PPH was compared in those exposed to CCBs to those exposed to methyldopa or labetalol. Propensity score matching and stratification were used to address potential confounding. Main outcome measuresThe occurrence of PPH during the delivery hospitalisation. ResultsThere were 27 patients exposed to CCBs (2.2%) and 232 patients exposed to methyldopa or labetalol (2.7%) who experienced PPH. After accounting for confounders, there was no meaningful association between CCB exposure and PPH in the propensity score matched (odds ratio 0.77, 95% CI 0.50-1.18) or stratified (odds ratio 0.79, 95% CI 0.53-1.19) analyses. Similar results were obtained across multiple sensitivity analyses. ConclusionsThe outpatient use of CCBs in late pregnancy for the treatment of hypertension does not increase the risk of PPH.