GnRH Agonist (GnRHa) Withdrawal at Late Stage of Long Protocol and the Incidence of Ovarian Hyper-stimulation

Inclusion Criteria: ninety-six infertile patients with PCOs (12 or more follicles 2-9 mm in diameter were detected in ovaries by ultrasound detection) undergoing IVF treatment were enrolled. Exclusion Criteria: the subjects included the followings: a basal FSH level of \> 10IU/L; age \>35 years; a body mass index (BMI) \> 30 kg/m2; ovarian surgery radiotherapy or chemotherapy; ovarian dysfunction; endometriosis; hyperprolactinemia; thyroid dysfunction; the presence of organic pelvic diseases.