Introduction: Genital tissues (ovary, endometrium and placenta) express GnRH receptors. GnRH plays essential roles in embryo implantation, invasion of trophoblastic tissue and steroid synthesis in the placenta. In IVF-ICSI cycles, the use of GnRH antagonists is limited to the last days of ovulation. The aim of this study was to evaluate the effects of GnRH antagonist at pharmacological doses given in the early implantation period on pregnancy. Materials and Methods: This retrospective study was performed in Yazd Research and Clinical Center for Infertility, 2014-2015. Women under 40 years old, with >20 follicles (>11mm) and risk of OHSS were included. Participants with history of endometriosis, hysteroscopy and history RIF were excluded. The treatment for all of participants was antagonist protocol. Twenty seven patients did not receive Cetrotide in luteal phase, and 67 patients received Cetrotide. Pregnancy outcomes were assessed based on chemical and clinical pregnancy. Results: Totally 94 patients were included. The mean age of participants was 28.40±4.25 years old. There were no differences in ART and demographic characteristics (p>0.05). The most frequent causes of infertility were: male factor (45.2%) and polycystic ovary syndrome (19.4%). The pregnancy outcome was not significantly different between Cetrotide and non Cetrotide group (p=0.224). Conclusion: The present study proposed that luteal phase GnRH antagonist administration does not influence the chance of successful pregnancy outcome. The incidence of chemical and clinical pregnancy in two groups was not significantly different.