RESUMEN
PURPOSE: To evaluate the effectiveness of the progestin-primed ovarian stimulation (PPOS) protocol versus the gonadotropin-releasing hormone antagonist (GnRH-ant) protocol in ovarian stimulation. METHODS: In this retrospective cohort study, we included 804 patients who were treated between January 1st, 2022, and July 1st, 2023. Outcomes of ovarian stimulation were compared between the PPOS (n = 206) and GnRH-ant (n = 598). The primary outcome was the number of good cleavage embryos. RESULTS: Baseline characteristics were comparable in both groups. In both unadjusted and adjusted analysis, the mean number of good cleavage embryos in PPOS (6.33) was non-inferior to GnRH-ant (6.44; unadjusted ratio of two means 1.02, 95%CI 0.92, 1.13). The trigger-day estradiol level in patients with PPOS was higher than in patients with GnRH-ant (4,420 vs 3,830 pg/ml, respectively) despite similar total follicle stimulating hormone dose and fewer days of ovarian stimulation. The number of oocytes, MII oocytes, cleavage and blastocyst embryos were comparable between the two protocols. After the first transfer of embryos, the clinical pregnancy rate and implantation rate were higher in the PPOS group, while the pregnancy rate and ongoing pregnancy were not significantly different. None of the PPOS patients had an unexpected LH surge, and serum LH levels decreased slightly during ovarian stimulation. CONCLUSIONS: The PPOS protocol with dydrogesterone provided similar embryo outcomes to the GnRH-ant protocol, with notable distinctions in clinical pregnancy and implantation rate. The serum LH concentration during ovarian stimulation using PPOS was well-controlled.