To test whether GnRHa withheld 2-3 days before ovulation trigger reduces the incidence of ovarian hyperstimulation syndrome (OHSS) in infertile high-risk patients with polycystic ovaries (PCOs) who have been treated with gonadotropins for in vitro fertilization (IVF) or Intracytoplasmic sperm injection (ICSI).

All the patients received a midluteal long GnRH agonist (GnRH-a) and a gonadotropins (recombinant FSH) stimulation protocol. Pituitary down-regulation with GnRH agonist (triptorelin, 0.1mg/d, ×10d, then 0.05mg/d until E2 ≤40 pg/ml in serum), was initiated during the luteal phase on the cycle-day 21. Two weeks later, if E2 in serum was ≤40 pg/ml and absence of follicular activity was detected, the stimulation of ovaries was started by recombinant follicle-stimulating hormone (recFSH, Gonal-F, Serono, Switzerland) with doses ranging 150-250 IU/d. Doses were adjusted accordingly with ovarian monitoring and follicles growth. GnRHa (0.05mg/d) was injected stimulously with FSH before dominant follicles were ≥ 14 mm. When the diameter of one or more follicles was ≥ 14 mm, GnRHa (0.05mg/d) was withheld in the study group. In the control group, GnRHa was used to the day of ovulation trigger. Ovulation was induced with HCG (5000-10000 IU) when at least three follicles greater than 16mm in diameter were detected on ultrasound examination and the leading follicles reached ≥ 18 mm in diameter. Oocytes retrieval for IVF or ICSI was performed 34-36 hours later under transvaginal ultrasound guidance. Main Outcome Measure(s): Serum E2 levels, VEGF levels in Serum and follicular fluids, retrieved oocytes, fertilization, implantation rate and pregnancy rate (PR), the rate of OHSS.