LAUSR

Context Ovarian stimulation (OS) increases pregnancy rates but can cause multiple folliculogenesis and multiple pregnancy. Objective To determine whether the probability of pregnancy differs in OS cycles with mono- vs multifolliculogenesis in women with unexplained infertility (UI). Design Secondary analysis of a multicenter, randomized controlled trial: Assessment of Multiple Intrauterine Gestations from Ovarian Stimulation with 3 treatment arms: gonadotropins, clomiphene, or letrozole, combined with intrauterine insemination. Women were categorized as having either 1 or ≥ 2 mature follicles (≥ 16 mm). Relative risk (RR) and 95% CIs for clinical pregnancy and live birth by number of follicles were estimated using generalized linear models adjusted for age, body mass index, years of infertility, and history of prior live birth. Setting 12 US-based clinical sites. Participants Normally cycling women aged 18 to 40 years with a normal uterine cavity and at least 1 patent fallopian tube. Male partners with ≥ 5 million total motile sperm. Interventions Gonadotropins, clomiphene, or letrozole with insemination. Main Outcome Measures Clinical pregnancy rates (CPR) and live birth rates (LBR). Results A single mature follicle > 16 mm resulted in lower CPR (RR, 0.70; 95% CI, 0.54-0.90) and LBR (RR, 0.67; 95% CI, 0.51-0.89) compared with ≥ 2 mature follicles. When stratified by treatment modality, no association of follicle number with CPR or LBR was observed for letrozole or clomiphene, but women using gonadotropins had lower CPR and LBR with monofolliculogenesis. Conclusion In couples undergoing gonadotropin treatment for UI, monofolliculogenesis following OS is related to a lower rate of live birth.