The Risk of Bleeding in Pregnant Women with Acute Venous Thromboembolism Treated with Anticoagulants: An International Multi-Database Cohort Study.

Background: Venous thromboembolism (VTE), including deep vein thrombosis (DVT) and pulmonary embolism (PE), is a major cause of maternal mortality. Low-molecular-weight heparin (LMWH) is the mainstay of therapy for VTE during pregnancy. However, the effects of different LMWH types and dosing regimens on bleeding risk remain unclear.

Methods: This multinational retrospective cohort study used population-level healthcare data from Québec, Canada, and Germany and included women with acute VTE during pregnancy who initiated therapeutic doses of LMWH within 15 days of incident VTE. We used Cox proportional hazards models to compare the risk of major bleeding associated with the most commonly prescribed LMWHs, dalteparin in Québec and enoxaparin in Germany, versus other LMWHs. Additionally, we examined the impact of once-daily versus twice-daily LMWH dosing on bleeding outcomes.

Results: The study cohort included 567 pregnant women (Germany n=308; Québec n=259) with VTE treated with LMWH. Major bleeding occurred in 6.5-7.7% of patients in both cohorts. The hazard ratios [95% confidence interval] for the most prescribed LMWH vs other LMWHs was 0.9 [0.3-2.5] in Québec and 1.4 [0.5-4.1] in Germany. No significant differences in bleeding risk were found between once-daily and twice-daily dosing schedules.

Conclusion: Our multinational cohort study provided population-based incidence rates for bleeding related to LMWH use during VTE treatment in pregnancy. Moreover, while hypothesis generating, our findings suggest that the LMWH type and dosing frequency may not influence bleeding risk in pregnant women with VTE. Further research is necessary to explore anticoagulation strategies to optimize outcomes and minimize bleeding complications.