Universal Aspirin Dispensation for Prevention of Preeclampsia in a High-Risk Population.

BACKGROUND: Hypertensive disorders of pregnancy are a major cause of maternal morbidity and mortality. Aspirin therapy has shown benefit in high-risk populations; however, current characteristic-based screening approaches are cumbersome, and risks of aspirin exposure are low, making universal prescribing appealing. OBJECTIVE: To report the effect of universal aspirin dispensation for preeclampsia prevention in a population with a high rate of hypertensive disorders. STUDY DESIGN: This observational cohort study includes all deliveries between April 2020 to July 2025 at Parkland Health, a high-volume obstetric service with community clinics capable of directly dispensing medication during prenatal visits. Patients who initiated prenatal care by 16 weeks gestation received 162mg aspirin daily beginning August 3, 2022, prior to this date aspirin was not recommended regardless of risk factors. Deliveries during the washout period (8/3/2022 - 2/3/2023) were excluded. The primary outcome was preeclampsia with severe features, which was a clinical diagnosis characterized by administration of magnesium sulfate for severe hypertension, lab abnormalities, or eclampsia. RESULTS: Two cohorts of 18,457 patients, before and after aspirin implementation, were compared. Patients in the aspirin epoch had a lower incidence of preeclampsia with severe features (6.9% vs. 5.1%, p<0.001), aOR 0.65(0.60-0.72). Additionally, the time to diagnosis of preeclampsia with severe features was longer in the aspirin epoch, p<0.001. Patients with chronic hypertension were also less likely to develop preeclampsia with severe features aOR 0.72 (0.59-0.86)) in the aspirin epoch. The rate of abruption, postpartum hemorrhage, and neonatal complications did not increase in the aspirin epoch. Pharmacy data confirmed at least 14,754 (80.4%) patients with a prenatal visit ≤ 16 weeks received aspirin during the later epoch, with median 180 tablets dispensed. CONCLUSIONS: Universal dispensation of 162mg aspirin daily at the first prenatal visit in a population with a high rate of hypertensive disorders was associated with a population-level reduction in the development of preeclampsia with severe features in patients with and without chronic hypertension, without an increase in abruption or postpartum hemorrhage. This study demonstrates the possible benefit of a universal approach to aspirin prescribing in high-risk populations, especially if direct dispensation is performed.