A Cochrane review [Abstract] 1 included 9 studies with a total of 2 716 women. There was no significant difference in live birth rate (OR 1.15, 95% CI 0.71 to 1.88; I² 29%; 3 studies n=468; low quality evidence). The evidence suggests that if the chance of live birth following single intrauterine insemination (IUI) is 16%, the chance of live birth following double IUI would be between 12% and 27%.
A meta-analysis 2 included 15 RCTs with a total of 3 795 women. The subgroup 'mild male infertility' included 1246 women whilst the subgroup 'normal semen quality' included 1188 women. Clinical pregnancy was reported by all studies, and there is no evidence of a difference between single and double IUI (RR 1.22, CI 0.97 to 1.54, 15 RCTs, 3 795 women, I² 45%). In the subgroup analysis, no particular group that could benefit was identified. Live birth, ectopic pregnancy, and miscarriage were reported in very few studies and the estimates were too imprecise.
Comment: The quality of evidence is downgraded by study quality (unclear allocation concealment and inadequate intention-to-treat adherence) and imprcise results (few events and wide confidence intervals).
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