Received November 11, 2017
Accepted June 11, 2018

Objective: This study aimed to evaluate the e ect of three days of GnRH antagonist pretreatment on the preg- nancy outcomes of women with polycystic ovarian syn- drome (PCOS) on GnRH antagonist protocols for IVF/ICSI. Methods: Fifty women with PCOS in the control group received conventional antagonist protocols, starting on day 2 of the cycle. In the pretreatment group (n=38), a GnRH antagonist was administered from day 2 of the menstrual cycle for three days. Results: Controlled ovarian stimulation (COS) duration and gonadotropin dosages were similar in both groups. The number of metaphase II (MII) oocytes, 2PN oocytes, embryos, along with implantation and clinical pregnancy rates, were higher in the pretreatment group when com- pared with controls, although the increment was not sig- ni cant (p value ≥0.05). The chemical pregnancy rate was signi cantly higher in the pretreatment group. The rate of OHSS was signi cantly lower in the pretreatment than in the control group. Conclusion: Women with PCOS o ered early follicular phase GnRH antagonist pretreatment for three consecu- tive days had signi cantly fewer cases of OHSS and higher chemical pregnancy rates. There were trends toward great- er numbers of MII oocytes, 2PN oocytes, and embryos, and higher clinical pregnancy rates in the pretreatment group.