Low-Dose Aspirin is Not Associated with Increased Risk of Postpartum Hemorrhage

Area of Science:

• Obstetrics and Gynecology
• Maternal-Fetal Medicine
• Pharmacology

Background:

• Aspirin (ASA) is recommended for preeclampsia prevention.
• Uncertainty exists regarding higher ASA doses (e.g., 150 mg/day) and postpartum hemorrhage (PPH) risk.
• Canadian formulation of ASA is 81 mg/day, with a hypothesis that 162 mg/day may increase bleeding risk.

Purpose of the Study:

• To evaluate the association between ASA 162 mg/day for preeclampsia prevention and the risk of PPH.
• To assess the risk of other maternal or neonatal bleeding events with ASA 162 mg/day.
• To compare bleeding risks between patients receiving ASA 162 mg/day and a low-risk control group.

Main Methods:

• Retrospective cohort study of patients using ASA 162 mg/day for preeclampsia prophylaxis (12-36 weeks' gestation).
• Control group received no ASA; exclusions included anticoagulant use and specific uterine/placental conditions.
• Primary outcome: PPH defined by transfusion, additional uterotonics, surgery, or tamponade; secondary outcomes: composite maternal bleeding.

Main Results:

• No significant difference in PPH between ASA (12.1%) and control (7.0%) groups (P=0.12).
• PPH risk was not significantly different in cesarean deliveries (8.3% vs 9.6%, P=0.44).
• Composite maternal hemorrhage rates were similar (65.5% vs 63.4%, P=0.58).

Conclusions:

• ASA 162 mg/day for preeclampsia prophylaxis is not associated with an increased risk of PPH.
• Higher-dose aspirin use in this context did not elevate other maternal or neonatal bleeding complications.
• Findings suggest safety regarding bleeding risks for ASA 162 mg/day in preeclampsia prevention.