Aspirin for in vitro fertilisation.

backgroundAspirin is used to improve the outcome in women undergoing in vitro fertilisation despite inconsistent evidence of its efficacy. The most appropriate time to commence aspirin therapy and the length of treatment required are also still to be determined. This is an update of the review first published in 2007.

objectivesTo determine the effectiveness and safety of aspirin for improving the outcome of in vitro fertilisation and intracytoplasmic sperm injection treatment cycles. SEARCH STRATEGY: We searched the Cochrane Menstrual Disorders and Subfertility Group Trials Register, Cochrane Central Register of Controlled Trials (CENTRAL) (The Cochrane Library January 2011), MEDLINE (1966 to January 2011) and EMBASE (1980 to January 2011) databases. We used the research terms: "(aspirin OR acetylsalicylic acid) AND (in-vitro fertilisation OR intracytoplasmic sperm injection)", combined with the Cochrane Menstrual Disorders and Subfertility Group's search strategy, in order to identify randomised controlled trials on aspirin for women undergoing in vitro fertilisation. SELECTION CRITERIA: Randomised controlled trials. DATA COLLECTION AND ANALYSIS: Two authors independently selected studies to include in the review, extracted data and assessed trial quality. MAIN

resultsThe searches identified 13 trials which were eligible for inclusion in the review, including a total of 2653 participants. No significant differences were found between the treatment and control groups for any of the outcomes assessed. No significant differences were found in the meta-analysis of studies investigating the effect of aspirin compared with control on live birth rate (RR 0.91, 95% CI 0.72 to 1.15; three studies and 1053 participants), clinical pregnancy rate (RR 1.03, 95% CI 0.91 to 1.17; 10 studies and 2142 participants), ectopic and miscarriage rates (RR 1.86, 95% CI 0.75 to 4.63; RR 1.10, 95% CI 0.68 to 1.77) respectively (three and five studies involving 1135 and 1497 participants). AUTHORS'

conclusionsUse of aspirin for women undergoing in vitro fertilisation cannot be recommended due to lack of evidence from the current trial data. Adequately powered trials are needed. It was proposed in the initial version of this review that a sample size of 350 women in each group would be required in order to demonstrate a 10% improvement from the use of aspirin, with 80% power at the 5% significance level. Until such evidence is available, this treatment can not be recommended.