Luteal-phase stimulation does not compromise embryo euploidy or live birth outcomes compared to follicular-phase stimulation

Background Aneuploidy is a major cause of implantation failure and miscarriage in assisted reproductive technology. This study aimed to evaluate embryo euploidy and live birth rates associated with the luteal-phase stimulation (LPS) protocol in in vitro fertilization (IVF), compared with the follicular-phase stimulation (FPS) protocol. Methods We conducted a retrospective cohort study at a university-affiliated fertility center, including 667 preimplantation genetic testing for aneuploidy (PGT-A) cycles performed between January 2020 and June 2023. After 1:1 propensity score matching, 106 cycles were analyzed from each group (LPS and FPS). Baseline characteristics, ovarian stimulation parameters, euploidy rate, and subsequent reproductive outcomes were compared. Results After matching, baseline characteristics were comparable between the groups. The LPS group required a longer duration of gonadotropin stimulation (median 10.5 vs. 9 days, p < 0.001) and yielded fewer retrieved oocytes (median 6 vs. 9, p < 0.05) than the FPS group. On the day of hCG administration, patients in the LPS group had significantly higher progesterone levels than those in the FPS group (median 6.1 vs. 3.1, p < 0.001). However, the euploidy rate did not differ significantly (33.9% vs. 30.8%, p > 0.05). Subgroup analyses stratified by age ( 0.05), live birth rate (41.2% vs. 46.2%, p > 0.05), and pregnancy loss rate (14.7% vs. 17.9%, p > 0.05) after the first embryo transfer were comparable. Conclusion The LPS protocol demonstrated similar embryo euploidy and live birth rates to the FPS protocol, suggesting that LPS does not compromise chromosomal competence or reproductive outcomes. However, the lower oocyte yield in the LPS group could potentially affect cumulative pregnancy and live birth rates. Given its scheduling flexibility, LPS may still represent a clinically feasible and patient-friendly option in assisted reproductive technology (ART).