Aspirin for Endometrial Preparation in Patients Undergoing IVF: A Systematic Review and Meta-analysis.

OBJECTIVE: To investigate the effect of aspirin on IVF success rates when used as an adjuvant treatment for endometrial preparation. DATA SOURCES: Relevant publications were comprehensively selected from PubMed, MEDLINE, Embase, and the Cochrane Central Register of Controlled Trials (CENTRAL) up to November 15, 2020. STUDY SELECTION: Randomized controlled trials (RCTs) and retrospective cohort studies that used aspirin as an adjuvant treatment for endometrial preparation and reported subsequent pregnancy outcomes were included. Studies were excluded if aspirin was used before and/or during ovarian stimulation. DATA EXTRACTION AND SYNTHESIS: This systematic review and meta-analysis included a total of 7 studies. Risk of bias assessment was based on the methodology and categories listed in the Cochrane Handbook for the RCTs and the Newcastle-Ottawa scale for the retrospective studies. The primary outcome was live birth rate. Summary measures were reported as odds ratios (ORs) with 95% confidence intervals (CIs). There was significant evidence that aspirin for endometrial preparation improved live birth rates (OR  1.52; 95% CI   1.15-2.00). No effect was noted for clinical pregnancy rates (OR  1.37; 95% CI   1.00-1.87); however, aspirin was associated with improved pregnancy rates in a subgroup analysis of patients receiving oocyte donation (OR 2.53; 95% CI 1.30-4.92) and in the sensitivity analysis (OR 1.3; 95% CI   1.02-1.66). No effect of aspirin was found for implantation or miscarriage rates (OR 1.31; 95% CI  0.51-3.36 and OR 0.41; 95% CI  0.02-7.42, respectively). CONCLUSION: These findings support a beneficial effect of aspirin for endometrial preparation on IVF success rates, mainly live birth rates, outside the context of ovarian stimulation. However, this evidence is based on poor quality data and needs to be confirmed with high-quality RCTs.