Women had standard pituitary down-regulation with GnRHa (Triptorelin 0.1mg, Decapeptyl® Ferring, Germany) day 7 after ovulation of previous cycle or on day 21 of the oral contraceptive cycles. GnRHa was continued for 2 weeks. Human menopausal gonadotrophin(HMG) (Merional ®IBSA) 150-300 IU/day was administered until the day of HCG administration, Transvaginal oocyte retrieval will be performed 34-36 h after the administration of HCG.