The use of IUI – intrauterine insemination appears to improve the chance for pregnancy when combined with either clomiphene citrate (CC) or gonadotropins such as Gonal F or Follistim. but does IUI increase the chance for pregnancy if used alone without fertility drugs? Unfortunately, there isn't very much data that has looked at this question. The best type of study is called a randomized controlled trial. IUI by itself, in couples with unexplained infertility, has been evaluated against intercourse in only one randomized trial. In this study, couples with unexplained infertility were split into one of two groups. One group was treated with IUI at the time of ovulation. The second group had only intercourse at the time of ovulation. Conceptions occurred in 6 of 145 (4.1%) IUI cycles and 3 of 123 (2.4%) intercourse cycles. Statistical analysis demonstrated that the results can arise by chance.
Another trial compared IUI with intracervical insemination (ICI). Although the study was not ideal for the evaluation of unexplained infertility because 25% of male partners had low sperm counts, the majority of patients had unexplained infertility; pregnancies occurred in 35 of 717 (4.9%) IUI cycles and 14 of 706 (2.0%) ICI cycles.
Combining the numbers from the two trials gives a rate of 4.76% with IUI and 2.05% with controls, and the absolute treatment effect was 4.76 minus 2.05 or 2.71. Thus, one would need to provide 100/2.71 or 37 cycles of IUI therapy to obtain a single additional pregnancy compared with control cycles.
In summary, based on these two trials, there is a significant but small effect of IUI therapy: 1 additional pregnancy in 37 IUI cycles compared with control cycles.