To investigate whether aspirin 81mg daily for preeclampsia prevention is associated with increased risk of postpartum blood loss at time of delivery.
A retrospective cohort study at a tertiary hospital from January 2018 to April 2021. Data were extracted from the electronic medical record. Patients prescribed LDA were compared to patients who were not. The primary outcome was a composite of postpartum blood loss, defined as: estimated blood loss (EBL) >1000 mL, documentation of ICD-9/10 codes for postpartum hemorrhage (PPH), or red blood cell (RBC) transfusion. Bivariate analysis, and unadjusted and adjusted logistic regression modeling were performed.
Among 16,980 deliveries, 1,922 (11.3%) were prescribed LDA. Patients prescribed LDA were more likely to be >35 years old, nulliparous, obese, taking other anticoagulants, or have diagnoses of diabetes, systemic lupus erythematosus, fibroids, or hypertensive disease of pregnancy. After adjusting for potential confounders, the significant association between LDA use and the composite did not persist, (aOR 1.1, 95% CI 1.0-1.3) nor did the association between EBL > 1000mL (aOR 1.0, 95% CI 0.9-1.3) and RBC transfusion (aOR 1.3, 95% CI 0.9-1.7). The association between LDA and PPH remained significant (aOR 1.3, 95% CI 1.1-1.6). Patients who discontinued LDA <7 days prior to delivery had an increased risk of the postpartum blood loss composite compared discontinuation ≥7 days (15.0% vs. 9.3%; p=0.03).
There may be an association between LDA use and increased risk of postpartum bleeding. This suggests that use of LDA outside the recommended guidelines should be cautioned and further investigation is needed to determine its ideal dosing and timing of discontinuation.

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