Ovulation Induction

Women undergoing IVF/ICSI who are candidates for a GnRH-antagonist protocol are randomly assigned 1:1 to oral linzagolix or the standard injectable GnRH antagonist (ganirelix or cetrorelix). A third, non-randomized group of women with a clinical indication for progestin-primed ovarian stimulation (PPOS) - for example, a need for a freeze-all strategy - is enrolled concurrently as a comparator cohort. The randomized comparison (linzagolix vs. injectable antagonist) is the primary, non-inferiority analysis; the PPOS cohort provides an exploratory, non-randomized comparison, analyzed with adjustment for baseline differences.

This randomized controlled trial (RCT) aims to evaluate whether, in infertile women with WHO II/IV ovulatory disorders, a combination of letrozole (LE) and clomiphene citrate (CC) compared to LE alone, result in higher live birth rates. The study is designed as an open-label, multicenter RCT across six fertility clinics in Vietnam. Participants will be randomized into two groups: (1) LE + CC , (2) LE alone. The primary outcome measure is the live birth rate after one treatment cycle. Based on prior data, the live birth rate for IUI in letrozole cycles is estimated at 12%. To detect a 10% increase in live birth rates with CC, 436 couples are needed (α = 0.05, power = 80%). Additionally, the live birth rate after IUI with LE-induced ovulation is approximately 18.7% (Diamond et al., 2015). To detect a 10% increase with CC, 560 couples are required (α = 0.05, power = 80%). Considering a 5% loss to follow-up and protocol deviations, the study plans to recruit 600 participants (150 per arm).