According to the results of the current study, following administration of 1500 IU hCG in GnRH antagonist cycles on the day of oocyte retrieval, the rate of severe OHSS significantly reduced, compared to administration of hCG 1500 IU + GnRH agonist at the same time, but there were no changes in the number of oocytes in metaphase II and rate of pregnancy. The gene discussed is GNRH1; the disease is ovarian hyperstimulation syndrome.