Eleven RCTs were included (n=1,279 couples). Seven were parallel-group trials, three were crossover trials, and one was a Latin square trial. Five reported the methods of randomisation and five reported adequate methods of allocation concealment. None of the trials were blinded.
For all trials, the difference in pregnancy rate between intrauterine insemination and control ranged from -22.4% to 23.8%. Insemination was associated with a non-statistically significant increase in pregnancy rate compared with control; rate difference 6% (95% CI -0.9 to 12.6). Significant heterogeneity was found (p=0.009). Heterogeneity was no longer significant for insemination versus control after omitting trials that used clomiphene as a cointervention; pooled rate difference 7.0% (95% CI -4.6 to 18.7; ten trials).
Insemination was associated with a non-statistically significant increase in pregnancy rate compared with timed intercourse; pooled rate difference 6.1% (95% CI -2.2 to 14.6; nine trials). Insemination was associated with a significant increase in pregnancy rate compared with expectant management; pooled rate difference 3.9% (95% CI 2.8 to 4.7; two trials). There was no significant heterogeneity between groups (p=0.82).
Adjusted indirect comparisons showed no statistically significant difference in pregnancy rate between timed intercourse and expectant management; pooled rate difference 2.2% (95% CI -6.3 to 10.7).
Results for sensitivity analyses were similar and no significant publication bias was found (p=0.54).