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The following is a summary of “Aspirin 162 mg vs 81 mg for preeclampsia prophylaxis in high-risk obese individuals: a comparative effectiveness open-label randomized trial (ASPREO),” published in the March 2025 issue of American Journal of Obstetrics & Gynecology by Amro et al. 

Inconsistent aspirin dosing recommendations for preeclampsia prevention and potential resistance in individuals with obesity may affect its effectiveness.  

Researchers conducted a retrospective study to compare the effectiveness of 162 mg vs 81 mg of aspirin in reducing preeclampsia with severe features in high-risk, pregnant individuals with obesity.  

They randomized individuals between May 2019 and November 2022 at 12–20 weeks of gestation with a body mass inde77654123x ≥30 kg/m² and at least 1 high-risk factor (history of preeclampsia in a prior pregnancy, at least stage I hypertension in the index pregnancy, pregestational diabetes, or gestational diabetes diagnosed before 20 weeks). Participants received either 162 mg or 81 mg of aspirin daily until delivery without blinding. The primary outcome was preeclampsia with severe features (preeclampsia or superimposed preeclampsia with severe features; eclampsia; or hemolysis, elevated liver enzymes, low platelet count syndrome), while secondary outcomes included preterm birth due 4to preeclampsia, small for gestational age, postpartum hemorrhage, abruption, and medication side effects. A sample size of 220 was determined using a preplanned Bayesian analysis with a neutral informative prior to estimating the posterior probability of benefit or harm.  

The results showed that 220 of 343 individuals (64.1%) were randomized, with the primary outcome available for 209 of 220 (95%). Baseline characteristics were similar, with median gestational ages at enrolment of 15.9 weeks in the 162 mg aspirin group and 15.6 weeks in the 81 mg group. Enrolment before 16 weeks occurred in 55 of 110 receiving 162 mg and 58 of 110 receiving 81 mg. The primary outcome was observed in 37 of 107 (35%) in the 162 mg group and 41 of 102 (40%) in the 81 mg group (posterior relative risk, 0.88; 95% credible interval, 0.64–1.22). Bayesian analysis showed a 78% probability of reduced primary outcome with 162 mg aspirin. Rates of indicated preterm birth due to preeclampsia (21% vs 21%), small for gestational age (6.5% vs 2.9%), abruption (2.8% vs 3.0%), and postpartum hemorrhage (10.0% vs 8.8%) were comparable. Medication adverse effects were similar across groups.  

Investigators concluded that 162 mg aspirin showed a potential benefit over 81 mg in reducing severe preeclampsia in adults with high-risk obesity. 

Source: ajog.org/article/S0002-9378(24)00729-4/abstract