Maternal age, body mass index, duration of infertility, proportion of previous conception, the proportion of IVF indications, antral follicle count (AFC), baseline follicle stimulating hormone (FSH), baseline luteinizing hormone (LH), oestradiol (E2), days of ovarian stimulation, endometrial thickness on day of trigger, number of oocytes, fertilization method and incidence of ovarian hyper-stimulation syndrome (OHSS) were comparable between the natural and HRT cycles. The gene discussed is BRD2; the disease is ovarian hyperstimulation syndrome.