Objectives : This study evaluated the safety and efficacy of the progesterone-primed ovarian stimulation (PPOS) coupled with gonadotropin (FSH) for infertile women with polycystic ovary syndrome (PCOS) who were assigned for ICSI and frozen blastocyst transfer.    
Patients : 200 infertile women were divided randomly into Group C, which received Cetrorelix injection (0.25 mg daily) on day-6, and Group S, which received oral dydrogesterone (20 mg/day) on day-2 of the menstrual cycle till the trigger day. All patients received an FSH injection of 225 IU daily from day-2 till triggering day. ICSI was performed and day-5 blastocysts underwent vitrification ultra-rapid cryopreservation till being transferred. Outcomes included the ability of PPOS to suppress the premature luteinizing hormone (LH) surge and prevent the development of ovarian hyperstimulation syndrome (OHSS), the incidence of profound LH suppression, the number of retrieved M2 oocyte and fertilization, chemical and clinical pregnancy rates, and the miscarriage rate.    
Results: No moderate-to-severe OHSS or premature LH surge was reported in all patients. Serum levels of estradiol and LH increased significantly in all patients with insignificant differences between both groups. The numbers of mature follicles on triggering day, retrieved M2 oocytes and D-5 good-quality blastocysts, pregnancy rates and the miscarriage rate showed non-significant differences between the studied groups.  
Conclusion: PPOS protocol for OS is safe and effective for infertile PCOS women. PPOS protocol achieved appropriate LH suppression with nearly no profound suppression or moderate-to-severe OHSS. The outcomes of PPOS protocol were comparable to the GnRH-antagonist protocol, however, PPOS is more cost-effective.