Ovarian Stimulation Strategies for Intrauterine Insemination in Couples with Unexplained Infertility - A Systematic Review and Individual Participant Data Meta-analysis

Abstract

Background: Intrauterine insemination with ovarian stimulation (IUI-OS) is a first-line treatment for couples with unexplained infertility. Individual participant data meta-analysis (IPD-MA) is the gold standard for evidence synthesis. Aim: To compare the effectiveness and safety of ovarian stimulation with gonadotrophin, Letrozole and clomiphene citrate (CC) and to explore treatment-covariate interactions for important baseline characteristics in women undergoing IUI. Method: We searched electronic databases including PubMed, MEDLINE, EMBASE, Cochrane Database of Systematic Reviews, Cochrane Central Register of Controlled Trials (CENTRAL). We included randomised controlled trials (RCTs) comparing IUI-OS with gonadotropins, Letrozole or CC among couples with unexplained infertility. We excluded dose comparing studies of the same drug. We contacted the authors of eligible RCTs to share the IPD and established the IUI IPD-MA collaboration. The primary effectiveness outcome was live birth and the primary safety outcome was multiple pregnancy. We used a one-stage approach using a random effects model. Results: Six RCTs (n= 2299) provided IPD. Gonadotropins increased the chance of a live birth compared to both CC (5 RCTs, 1946 women, RR 1.28, 95%CI 1.10 to 1.49, I2 = 25%, moderate-quality evidence) whereas there was insufficient evidence of a difference between Letrozole and CC (1 RCT, 599 women, RR 0.77 95%CI 0.58 to 1.03). Gonadotropins increased the risk of a multiple pregnancy compared to both CC (4 RCTs, 1696 women, RR 2.17, 95%CI 1.33 to 3.55, I2 = 69%, low-quality evidence) whereas there was insufficient evidence of a difference between Letrozole and CC (1 RCT, 599 women, RR 0.71, 95%CI 0.33 to 1.56). No strong evidence on the treatment-covariate interactions (female age, BMI or primary versus secondary infertility) was found. Conclusion: Gonadotropins increased the chance of a live birth compared to both CC and Letrozole but also increased the chance of a multiple pregnancy. Further RCTs comparing Letrozole and other interventions in couples with unexplained infertility are needed.