Abbas Aflatoonian - M.D Research and Clinical Center for Infertility, Yazd Reproductive Sciences Institute, Shahid Sadoughi University of Medical Sciences, Yazd,Iran.
Mahnaz Mansoori-Torshizi - M.D. Novin Infertility Center, Mashhad,Iran
Maryam Farid Mojtahedi - M.D., Department of Obstetrics and Gynecology, Endocrinology and Female Infertility Unit, Roointan Arash Women s Health Research and Educational Hospital, TehranUniversity of Medical Sciences, Tehran, Iran.
Behrouz Aflatoonian - Ph.D.Stem Cell Biology Research Center,Yazd Reproductive Sciences Institute, Shahid Sadoughi University of Medical Sciences, Yazd, Iran. . Department of Reproductive Biology, School of Medicine, Shahid Sadoughi University of Medical Sciences, Yazd, Iran.

Background: The use of embryo cryopreservation excludes the possible detrimental effects of ovarian stimulation on the endometrium, and higher reproductive outcomes following this policy have been reported. Moreover, gonadotropinreleasing hormone agonist trigger in gonadotropin-releasing hormone (GnRH) antagonist cycles as a substitute for standard human chorionic gonadotropin trigger, minimizes the risk of ovarian hyperstimulation syndrome (OHSS) in fresh as well as frozen embryo transfer cycles (FET). Objective: To compare the reproductive outcomes and risk of OHSS in fresh vs frozen embryo transfer in high responder patients, undergoing in vitro fertilizationtriggered with a bolus of GnRH agonist. Materials and Methods: In this randomized, multi-centre study, 121 women undergoing FET and 119 women undergoing fresh ET were investigated as regards clinical pregnancy as the primary outcome and the chemical pregnancy, live birth, OHSS development, and perinatal data as secondary outcomes.Results: There were no significant differences between FET and fresh groups regarding chemical (46.4% vs. 40.2%, p=0.352), clinical (35.8% vs. 38.3%, p=0.699), and ongoing (30.3% vs. 32.7%, p=0.700) pregnancy rates, also live birth (30.3% vs. 29.9%, p=0.953), perinatal outcomes, and OHSS development (35.6% vs. 42.9%, p=0.337). No woman developed severe OHSS and no one required admission to hospital. Conclusion: Our findings suggest that GnRHa trigger followed by fresh transfer with modified luteal phase support in terms of a small human chorionic gonadotropin bolus is a good strategy to secure good live birth rates and a low risk of clinically relevant OHSS development in in vitro fertilization patients at risk of OHSS.

Fresh embryo transfer, Fresh, Frozen-thawed embryo transfer, GnRH antagonist,GnRHa trigger, OHSS, Reproductive Outcome