• Ashley I Naimi, Neil J Perkins, Lindsey A Sjaarda, Sunni L Mumford, Robert W Platt, Robert M Silver, and Enrique F Schisterman.
• Emory University, Atlanta, Georgia (A.I.N.).
• Ann. Intern. Med. 2021 May 1; 174 (5): 595601595-601.

BackgroundA previous large randomized trial indicated that preconception-initiated low-dose aspirin (LDA) therapy did not have a positive effect on pregnancy outcomes. However, this trial was subject to nonadherence, which was not taken into account by the intention-to-treat approach.ObjectiveTo estimate per protocol effects of preconception-initiated LDA on pregnancy loss and live birth.DesignThe EAGeR (Effects of Aspirin on Gestation and Reproduction) trial was used to construct a prospective cohort for a post hoc analysis. (ClinicalTrials.gov: NCT00467363).Setting4 university medical centers in the United States.Participants1227 women between the ages of 18 and 40 years who had 1 or 2 previous pregnancy losses and were attempting pregnancy.MeasurementsAdherence to LDA or placebo, assessed by measuring pill bottle weights at regular intervals during follow-up. Primary outcomes were human chorionic gonadotropin (hCG)-detected pregnancies, pregnancy losses, and live births, determined by pregnancy tests and medical records.ResultsRelative to placebo, adhering to LDA for 5 of 7 days per week led to 8 more hCG-detected pregnancies (95% CI, 4.64 to 10.96 pregnancies), 15 more live births (CI, 7.65 to 21.15 births), and 6 fewer pregnancy losses (CI, -12.00 to -0.20 losses) for every 100 women in the trial. In addition, compared with placebo, postconception initiation of LDA therapy led to a reduction in the estimated effects. Furthermore, effects were obtained in a minimum of 4 of 7 days per week.LimitationThe EAGeR trial data for this study were analyzed as observational data, thus are subject to the limitations of prospective observational studies.ConclusionPer protocol results suggest that preconception use of LDA at least 4 days per week may improve reproductive outcomes for women who have had 1 or 2 pregnancy losses. Increasing adherence to daily LDA seems to be key to improving effectiveness.Primary Funding SourceNational Institutes of Health.

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