Low-Dose Aspirin Prophylaxis for Preeclampsia and the Risk of Postpartum Hypertensive Outcomes: A Propensity Score Analysis

Abstract

The U.S. Preventive Services Task Force (USPSTF) recommends low-dose aspirin (LDA, 81 mg/day) after 12 weeks of pregnancy to reduce preeclampsia risk. While its effectiveness for prevention is well-established, less is known about the effects on postpartum hypertensive outcomes. This study aimed to examine whether LDA prescription in pregnancy (≤36 weeks' gestation) is associated with postpartum hypertensive outcomes through 6 weeks postpartum.

This retrospective cohort study used electronic medical record data from deliveries (2018–2019) at New England's largest safety-net hospital. Among 1,773 patients meeting USPSTF criteria for LDA initiation, 523 were prescribed LDA. Patients were propensity score (PS)-matched 1:1 on risk factors and prenatal care site (primary matched cohort: n = 784); a secondary PS-matched analysis was restricted to patients with one or more high-level risk factors (high-risk matched cohort: n = 212). Primary outcomes included antihypertensive use during hospitalization, antihypertensive prescription at discharge, and severe-range postpartum hypertension. Risk ratios (RRs) were estimated using log-binomial regression. Joint effects of LDA and preeclampsia were assessed using LDA −/PreE− as reference.

In the primary matched cohort, compared with LDA− patients, LDA+ patients had higher rates of antihypertensive use during hospitalization (RR: 1.54, 95% confidence interval [CI]: 1.12–2.12), discharge prescription (RR: 1.42, 95% CI: 0.95–2.12), and severe-range hypertension (RR: 1.48, 95% CI: 1.06–2.06). Associations did not persist in the high-risk matched cohort. In joint effects analyses, preeclampsia was associated with postpartum hypertensive outcomes regardless of LDA. Compared with LDA −/PreE − , the LDA +/PreE+ group had elevated risks; point estimates were highest among LDA −/PreE+ patients.

Associations between LDA and postpartum hypertensive outcomes may vary by baseline risk. Among high-risk patients, LDA was not associated with increased postpartum risk and may attenuate severity for those developing preeclampsia. Further study is needed to clarify LDA's role in reducing postpartum cardiovascular risk.