The effect of withholding gonadotropin (a coasting period) on the outcome of in vitro fertilization cycles.

OBJECTIVE: The purpose of this study was to evaluate the effects of coasting (withdrawing gonadotropin administration) on the cycle outcomes, including total number and quality of oocytes and embryos and pregnancy rate in patients undergoing in vitro fertilization.

STUDY DESIGN: Sixty-seven patients undergoing coasting were evaluated in a retrospective study at the Royan Institute between May 2002 and June 2003. All patients underwent standard long protocol with gonadotropin-releasing hormone (GnRH) analogue and human menopausal gonadotropin (HMG) and then in vitro fertilization and embryo transfer (IVF-ET). Coasting was considered when the estradiol level was more than 3000 pg/ml and the number of follicles >10 in each ovary. HCG was administered whenever estradiol reached < or =3000 pg/ml and then the (IVF-ET) program was carried out. According to coasting periods, patients were divided into two groups: coasting period < or =3 days and coasting period >3 days. Statistical comparisons were performed using Student's t test and Fisher's exact test.

RESULTS: There were no significant differences between the two groups with regard to mean age, body mass index (BMI), number of polycystic ovary syndrome (PCOS) patients, number of HMG ampoules and stimulation duration. The total number of retrieved oocytes decreased significantly in patients with more than 3 days of coasting (P=0.04). The number of high quality oocytes also decreased in this group; however, this did not reach significant levels. There were no significant differences between the two groups with regard to fertilization and pregnancy rate. None of the patients developed severe ovarian hyperstimulation syndrome (OHSS).

CONCLUSION: This study reveals that a long coasting period (>3 days) has a negative effect on the number of oocytes, although the fertilization and pregnancy rates are not affected. Prospective randomized studies with larger sample sizes are needed to compare coasting with other procedures.