Gamete intrafallopian transfer vs superovulation with intrauterine insemination for the treatment of infertility.

Superovulation with intrauterine insemination (SO-IUI) has been suggested as an alternative to gamete intrafallopian transfer (GIFT), despite the absence of controlled or comparative trials. We retrospectively analyzed all GIFT and SO-IUI cycles performed concurrently from January 1985 to August of 1987 at a single university center. Pregnancy rates were significantly better for GIFT than SO-IUI (P less than 0.001), with an odds ratio of 3.25 (P = 0.001). Stepwise multiple logistic regression identified factors that correlate with pregnancy: absence of endometriosis (P = 0.05), infertility less than 3 years' duration (P = 0.002), TMS greater than or equal to 30 X 10(6) (P = 0.005), and treatment with GIFT rather than SO-IUI (P = 0.001). These data give a first approximation of the increased efficacy of GIFT versus SO-IUI and provide valuable insight into significant confounding variables to be considered when planning a randomized, prospective trial to evaluate these techniques.