Controlled ovarian hyper-stimulation was performed using a short-acting GnRH agonist long protocol. Recombinant follicle-stimulating hormone (Merck Serono) was started at least 14 days after the downregulation of GnRH agonist for complete suppression of estradiol from 75 to 300IU/d. Ovulation was induced with human chorionic gonadotropin, and approximately 36 hours later, oocyte retrieval was performed under transvaginal ultrasonographic guidance. Fertilization was carried out using the standard IVF technique; if male infertility or fertilization failure occurred, oocytes were inseminated by ICSI. Embryo transfer was mostly performed using cleaving stage embryos (day 3). If a patient was at risk of ovarian hyperstimulation syndrome, the embryo was vitrified and transferred to a subsequent substituted cycle.