To test whether long-acting Triptorelin on pituitary down-regulation can improve the clinical pregnancy rate and reduces the incidence of ovarian hyperstimulation syndrome (OHSS) in infertile high-risk patients with polycystic ovaries (PCOs) who underwent in vitro fertilization (IVF) or Intracytoplasmic sperm injection

All patients received standard ovarian stimulation with rFSH under pituitary suppression with GnRH agonist according to a protocol used routinely. The long-acting Triptorelin group use long-acting Triptorelin 1.875mg during the luteal phase on Pituitary down-regulation , the Short acting Triptorelin use short-acting Triptorelin 0.1mg/d,x10d, then 0.05mg/d until E2\<40pg/ml in serum, was initiated during the luteal phase. Gonadotrophin stimulation of the ovaries was started when serum E2 concentrations declined to \< 40 pg/ml and a vaginal ultrasonographic scan showed an absence of follicles \> 10mm diameter. Ovarian stimulation was started wih 150-250 IU/day of recombinant FSH (Gonal F, Serono, Switzerland); the initial dose was determined by clinical judgement of the clinician according to the patients's age, body mass index, basal FSH and E2. Transvaginal ultrasound and E2 measurement were used to monitor follicular growth, and gonadotropin dosages were adjusted accordingly. Ovulation was triggered by intramuscular administration of 5000-10,000 IU of human chorionic gonadotropin (HCG, Ferring Pharmaceuticals) when at least two follicles reached a diameter of 18 mm. Serum HCG value were measured at 12 h after HCG trigger using the immunoassay. Oocytes were retrieved 36 h after the injection of HCG.