ABSTRACT
OBJECTIVE: To evaluate the effect of aspirin dose on the incidence of all gestational age preeclampsia and preterm preeclampsia. DATA SOURCES: Electronic databases (Cochrane, PubMed, Scopus, ClinicalTrials.gov and the Web of Science) were searched for articles published between January 1985 and March 2019 with no language restrictions. METHODS: We followed the PRIMSA guidelines and utilized Covidence software. Articles were screened by 2 independent reviewers, with discrepancies settled by an independent 3rd party. Study selection criteria were randomized trials comparing aspirin for prevention of all gestational age and preterm preeclampsia to placebo or no antiplatelet treatment in women aged 15-55 years with moderate or high-risk factors according to the list of risk factors from American College of Obstetricians and Gynecologists and United States Preventive Services Task Force guidelines. The quality of trials was assessed using the Cochrane risk of bias tool. The data were pooled using a random-effects meta-analysis comparing aspirin at doses of <81, 81, 100, and 150 mg. Pre-specified outcomes were all gestational age and preterm preeclampsia. RESULTS: Of 1,609 articles screened, 23 randomized trials, which included 32,370 women, fulfilled the inclusion criteria. In preterm preeclampsia, women assigned at random to 150 mg experienced a significant 62% reduction in risk of preterm preeclampsia (RR = 0.38; 95% CI: 0.20-0.72; P = 0.011). Aspirin doses <150 mg produced no significant reductions. The number needed to treat with 150 mg of aspirin was 39 (95% CI: 23-100). There was a maximum 30% reduction in risk of all gestational age preeclampsia at all aspirin doses. CONCLUSIONS: In this meta-analysis, based on indirect comparisons, aspirin at a dose greater than the current, recommended 81 mg was associated with the highest reduction in preterm preeclampsia. Our meta-analysis is limited due to the deficiency of homogeneous high evidence data available in the literature to date; however, it may be prudent for clinicians to consider that the optimal aspirin dose may be higher than the current guidelines advise. Future research to compare the efficacy aspirin doses greater than 81 mg is recommended. STUDY REGISTRATION: PROSPERO, CRD42019127951 (University of York, UK; http://www.crd.york.ac.uk/PROSPERO/).