The study was conducted in the Infertility Department of Shariati Hospital, a teaching hospital affiliated to Tehran University of Medical Sciences during 2006-2008. The project was approved by the Ethics Committee of the Infertility Department, and was initiated after obtaining written consents of the participants. High risk patients were defined as young females, who had antral follicle counts of more than 15, poly cystic ovaries on ultrasound scan and/or polycystic ovarian syndrome (PCOS), serum estradiol of more than 3500 pg/ml and/or multiple follicular recruitments Inhibitors,research,lifescience,medical in both ovaries during ultrasound monitoring in controlled

ovarian hyperstimulation (COH). The inclusion criteria were an age of less than 33 years, high risk of developing OHSS in the absence of taking antipsychotic medications, no known allergy to cabergoline or ergot alkaloids, and absence of hepatic dysfunction or hypertension. Polycystic Inhibitors,research,lifescience,medical ovarian syndrome was diagnosed according to Rotterdam criteria.8 According to the Rotterdam criteria, patients with two of the three characteristics including: 1) oligomenorrhea/amenorrhea, 2)

clinical (hirsutism) finding of hyperandrogenism, or 3) polycystic ovaries Inhibitors,research,lifescience,medical on transvaginal sonography, were included in the study. Metabolic features of PCOS patients were not of concern in this study; therefore, insulin resistance and androgen index were Inhibitors,research,lifescience,medical not measured. The oligomenorrhea/amenorrhea and polycystic appearance of ovaries were seen in more than two third of the PCOS patients. All PCOS patients were treated with metformin (1500 mg/day). Few of the patients had positive history of OHSS, regardless of its severity. All of the participants underwent controlled ovarian Inhibitors,research,lifescience,medical hyperstimulation (COH) with Gonadotropin/GnRH-agonist long protocol. All of them received folic acid (one mg/day) before Protein Tyrosine Kinase inhibitor initiating the induction cycle, low dose oral contraceptive pills (on the third of

the previous cycle) and doxycycline (100 much mg twice a day) for the first 10 days of the previous cycle. Long term desensitization protocol using subcutaneous GnRH agonist Buserelin (500 µg) was started on the day 21 of the previous cycle. After complete desensitization, ovarian stimulation using recombinant-FSH (Gonal F, Serono, switzerland) was commenced on day 3 of the next cycle at a daily dose 150 IU. Transvaginal ultrasound (Siemens, Sonoline G20) was done every 3-5 days for the examination of follicular development, and serum estradiol levels were measured every 2-3 days using radioimmunoassay method. When at least two follicles with diameter of at least 17 mm were observed, final oocyte maturation was triggered with 10,000 IU human chorionic gonadotropin (HCG, Ferring, Germany) administered as a single intramuscular injection.