Late-Start Corifollitropin Alfa in Mild Ovarian Stimulation

This prospective randomized clinical study evaluates a novel physiology-oriented mild ovarian stimulation protocol based on the delayed initiation of corifollitropin alfa. Unlike conventional ovarian stimulation, which begins during the early follicular phase, the proposed protocol postpones exogenous gonadotropin administration until cycle day 4, allowing physiological follicular recruitment to occur before ovarian stimulation. Participants are randomly assigned to one of two strategies for prevention of premature luteinizing hormone (LH) surge: daily GnRH antagonist administration, or progesterone-primed ovarian stimulation (PPOS). The primary objective is to evaluate ovarian response and the feasibility of this simplified stimulation strategy. Secondary objectives include embryological outcomes, pregnancy outcomes, gonadotropin consumption, treatment burden, and the proportion of patients completing stimulation without supplementary gonadotropin administration. The study aims to determine whether a physiology-oriented late-start stimulation protocol can simplify IVF treatment while maintaining satisfactory embryological and clinical outcomes.