PURPOSE: The aim was to investigate the value of the application of a progesterone-primed ovarian stimulation (PPOS) protocol in patients with ovarian endometriosis (OEM) combined with diminished ovarian reserve (DOR). MATERIALS AND METHODS: A retrospective analysis of 95 patients with OEM combined with a DOR who underwent in vitro fertilization/intracytoplasmic sperm injection-embryo transfer (IVF/ICSI-ET) was conducted between March 2020 and February 2024 at the Reproductive Center of Xuzhou Central Hospital. Patients were divided into two groups on the basis of the ovarian stimulation protocol used: the PPOS group (n = 60, 60 cycles) and the GnRH agonist downregulation group (n = 35, 35 cycles). General data, ovarian stimulation outcomes, and pregnancy outcomes were compared between the two groups. RESULTS: There were no statistically significant differences between the two groups in terms of general data (P >
0.05). Compared with the PPOS group, the GnRH agonist group presented significantly more Gn days and higher Gn dosages (P <
0.05). However, there were no significant differences between the groups in terms of the number of oocytes retrieved, metaphase II oocyte rate, fertilization rate, cleavage rate, high-quality embryo rate, or cycle cancellation rate (P >
0.05). Additionally, no significant differences were observed in the embryo transfer parameters, endometrial thickness, embryo implantation rate, clinical pregnancy rate, ectopic pregnancy rate, or early miscarriage rate (P >
0.05). CONCLUSIONS: In patients with OEM combined with DOR, the PPOS protocol had pregnancy outcomes comparable to those of the downregulation protocol, with the added advantage of being more cost-effective.