Abstract: AIM: To investigate the role of triggering ovulation and prevention of ovarian hyperstimulation syndrome (OHSS) by gonadotropin-releasing hormone agonist (GnRH-a) instead of human chorionic gonadotropin (HCG) in ovarian hyperresponders to human menopausal gonadotropin (HMG) treatment.METHODS: Research group involved 65 patients with high risk of developing OHSS, and they were given single dose subcutaneous injection of 0.2 mg triptorelin to trigger ovulation and prevent OHSS.Luteal support was initiated after ovulation with daily injections of 40 mg progesterone.There were 48 patients in control group, and 8 of them appeared ovarian hyperresponse to HMG and discontinued the treatment.40 patients were given HCG 5000 -10000 IU when follicles reached maturation.RESULTS: On the day of triptorelin injection the mean serum oestradiol concentration was 3.8 ±0.9 ng·L^-1 (range 2.9 -5.8 ng·L^-1)and the mean number of follicles ≥11 mm was 25.4 ±8.3 (range 18 -35).After triptorelin was administered,ovulation was effectively triggered in all of 65 patients, and the mean number of ovulation was 5.6 ±3.3 (range 1 -10).None of the patients developed signs or symptoms of severe OHSS.There were 18 (27.7 %) clinical pregnancies and 3 abortions.Ovulation rate and pregnancy rate showed no difference in comparison with control group, and none of research group discontinued the treatment.CONCLUSION: When the GnRH-a is not used before ovarian stimulation to pituitary down-regulation, adequate single dose of short-effect GnRH-a is able to effectively trigger an endogenous LH FSH surge, resulting in final oocyte maturation and ovulation, and furthermore it may effectively prevent OHSS.This strategy is special benefit to high responders with an increased risk of developing OHSS.

Key words: gonadotropin-releasing hormone agonist, triggering ovulation, ovarian hyperstimulation syndrome, Human chorionic gonadotropin