Unlocking Success: The Optimal Gonadotrophin Starting Point for Luteal-Phase Stimulation in IVF Patients with Normal Responses.

Purpose: To analyze and discover the optimal gonadotrophin (Gn) starting point for luteal-phase stimulation (LPS) in in vitro fertilization (IVF) Patients with normal ovarian response (NOR). Patients and Methods: A total of 199 IVF or intracytoplasmic sperm injection (ICSI) cycles performed at the Reproductive Center of the First Hospital of Jilin University from January 1, 2021, to December 31, 2023, were recruited in the study. Of these, 121 cycles followed the follicular phase ovarian stimulation (FPS) (119 cases of adding antagonists), while 78 cycles adhered to the LPS protocol. The LPS group was divided into three subgroups based on the timing of Gn initiation: early, mid-, and late LPS. Comparisons were made between the LPS and FPS groups, as well as among the three subgroups, regarding Gn duration, total Gn dose, number of oocytes retrieved, number of embryos, rate of good-quality embryos, blastocyst formation rate, clinical pregnancy rate, cumulative pregnancy rate, live birth rate and cumulative live birth rate. Results: The rate of high-quality embryos in the late luteal phase was significantly higher than that in the early luteal group and slightly higher than that in the mid-luteal group. The clinical pregnancy rate and live birth rate of the late luteal group were slightly higher than those of the early and mid-luteal group, and were not significantly different from those of the FPS group. Conclusion: Initiating Gn stimulation during the late luteal-phase appears to be the optimal timing in NOR patients.