Studies of any design that evaluated the effects of low-dose aspirin (150 mg or less given once daily), alone or combined with heparin or glucocorticoids, on the outcome for women undergoing IVF or ICSI were eligible for inclusion.
In the included studies, 75 to 100 mg/day aspirin was started at different stages of the treatment cycle and continued for varying durations. Some studies were in unselected patients and others were in selected IVF populations (the selection criteria varied). The review outcomes included pregnancy rate per embryo transfer (ET), clinical pregnancy rate per cycle or ET, clinical pregnancy rate per elective single ET, spontaneous abortion or ectopic pregnancy rate per clinical pregnancy, live birth rate per cycle or ET, implantation rate and cycle cancellation rate. Control groups received placebo or no treatment; in one study the controls received prednisone.
Two reviewers independently selected the studies and resolved any disagreements by consensus.