Treatment protocol All of the patients were treated with long protocol for ovarian stimulation. For pituitary suppression down regulation , the patients were treated with daily administration of 0.5 mg buserelin subcutaneous from day 21 of previous menstrual cycle. When desensitization was occurred, as evidenced by plasma E2 levels of ≤ 50 pg/ml and the absence of ovarian cyst on transvaginal ultrasound examination , buserelin was reduced to 0.25 mg/day and continued until the day of hCG administration. The COH was initiated with recombinant FSH or HMG 150 IU/day on the day 2 of menstrual cycle. Ovarian response was monitored by serial ultrasound examinations and evaluation of serum E2 levels, and then gonadotropin doses adjustment was done as required. Urinary HCG 10000 IU was administered when ≥3 follicles more than 18 mm.