A Cochrane review included 13 studies with a total of 2 653 subjects. No significant differences were found between the treatment (aspirin 80-100mg/day) and control groups for any of the outcomes assessed; for live birth rate RR 0.91 (95% CI 0.72 to 1.15; 3 studies, n=1053), for clinical pregnancy rate RR 1.03 (0.91 to 1.17; 10 studies, n=2142), and for miscarriage rate RR 1.10 (0.68 to 1.77; 5 sudies, n=1497). No data were reported on adverse events related to aspirin treatment.
Comment: The quality of evidence is downgraded by imprecise results (few studies assessing live birth rate which is the most important outcome) and by heterogeneity in interventions (dosage, timing).