Background: Ovarian Stimulation Response (OSR) in polycystic ovarian syndrome (PCOS) ladies is controversial issues .Aim: to evaluate outcomes of Fixed Progestin-Primed Ovarian Stimulation (FPPOS) and Flexible GnRH Antagonist Protocol (FGnRHan) on OSR and pregnancy outcomes in PCOS ladies undergone intracytoplasmic sperm injection-frozen embryo transfer (ICSI-FET). Patients and Methods: A retrospective assessment of PCOS ladies undergoing ICSI-FET cycles at Riyadh fertility center, Agouza, Giza Governorate (RFC) and Benha University Hospital (BUH), over the last 5 years. The frequencies of clinical pregnancy, continued pregnancy, live births, fertilization, early LH surge, and other OSR results were the outcomes. Results: of 950 ladies included, 420 had FPPOS (study group) and 390 (control group) had the GnRHan protocol. Both groups' baseline metrics showed similarities. Oocytes that were mature and fertilized showed no discernible difference between the two groups (P > 0.5). Premature luteinization was rare in both groups, and there was no statistically significant difference (P > 0.5). Additionally, there was no discernible difference in the clinical pregnancy rate per frozen embryo transfer cycle (FETC) between the FGnRHan and FPPOS groups (P > 0.5). Also, continuing pregnancy rates, miscarriage rates, biochemical pregnancy rates, and implantation rates, showed statistically similarities across the groups (P > 0.05). Although there

was a considerable decrease in cost calculated in local currency (5.8±3.1 vs. 8.8±4.1, p =0.001) between the FPPOS and FGnRHan groups. Conclusion: in PCOS ladies who had ICSI-FET, the FPPOS protocol proves to be a powerful, practical, user-friendly, economical, and clinically equivalent alternative to the standard FGnRHan protocol.