Low-dose aspirin for in vitro fertilisation

Low-dose aspirin is sometimes used to improve the outcome in women undergoing in vitro fertilisation, despite inconsistent evidence of efficacy and the potential risk of significant side affects. The most appropriate time to commence aspirin therapy and length of treatment required is also still to be determined.

To determine the effectiveness of low-dose aspirin for improving the outcome of in vitro fertilisation and intracytoplasmic sperm injection treatment cycles.

We searched the Cochrane Menstrual Disorders and Subfertility Group Trials Register, Cochrane Central Register of Controlled Trials (April 2007), MEDLINE (1966 to March 2007) and EMBASE (1980 to March 2007) databases using the following 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 for identifying randomised controlled trials for reports which appeared to describe randomised controlled trials of low-dose aspirin for women undergoing in vitro fertilisation.

Prospective randomised controlled trials, published or unpublished, which addressed the objectives of the review. Quasi-randomised trials were excluded.

Two authors independently selected studies to include in the review, extracted data and assessed trial quality.

The searches identified nine trials which were eligible for inclusion in the review, including a total of 1449 participants. No significant differences were found between the treatment and control groups for any of the outcomes assessed. Only two studies (involving 401 participants) investigated the effect of low-dose aspirin on live birth rate, and no significant difference was found between the treatment and control groups (RR 0.94, 95% CI 0.63 to 1.39). No significant difference was found in clinical pregnancy rate between treatment and control groups, based on results from 1240 participants in seven studies (RR 1.09, 95% CI 0.83 to 1.43). No data were reported on adverse events related to aspirin treatment in any of the included studies.

Use of low-dose aspirin for women undergoing in vitro fertilisation cannot currently be recommended due to lack of adequate trial data. There is a need for randomised controlled trials investigating the use of low-dose aspirin for different patient groups undergoing in vitro fertilisation. We used control group data from the largest trial included in this review to determine 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 evidence from appropriately powered trials is available, this treatment can not be recommended.