Evidence of absence or absence of evidence? A reanalysis of the effects of low-dose aspirin in in vitro fertilization

Objective: To assess the conflicting evidence whether low-dose aspirin is beneficial in IVF and to evaluate the meta-analysis performed by Gelbaya et al. and reported in March 2007 in Human Reproduction Update, in which they found no effects of low-dose aspirin and recommended discontinuing its use in IVF. We present a reanalysis of the effects of low-dose aspirin in IVF and raise methodological questions regarding the analysis by Gelbaya et al. Design: A meta-analysis of prospective randomized trials evaluating the effects of low-dose aspirin in IVF. Patient(s): Women undergoing IVF/intracytoplasmic sperm injection. Intervention(s): Low-dose acetylsalicylic acid (aspirin). Main Outcome Measure(s): Pregnancy rates, implantation rates, miscarriage rates. Result(s): Ten randomized clinical trials were included in the analysis. Clinical pregnancy rate per ET was significant when low-dose aspirin was compared with no treatment (risk ratio 1.15, 95% confidence interval 1.03-1.27). Nonsignificant estimates comparing low-dose aspirin with no treatment were found for implantation and miscarriage rates. Conclusion(s): Our results suggest that aspirin may increase clinical pregnancy rates and that more data are needed to resolve the issue. At this point, there is no reason to change clinical management and discontinue the use of aspirin.