OBJECTIVE: The purpose of this study was to investigate the efficacy of a flexible protocol of starting gonadotropin-releasing hormone antagonist according to the size of the leading follicle.

STUDY DESIGN: This was a pilot study that included 123 couples who were undergoing in vitro fertilization/intracytoplasmic sperm injection cycles at the Egyptian IVF-ET Center. Couples were recruited into two groups: group I (n=64), gonadotropin-releasing hormone antagonist was administered when the diameter of the leading follicle reached 16 mm; group II (n=59), gonadotropin-releasing hormone antagonist was administered on day 6 of stimulation.

RESULTS: The mean number of antagonist injections was significantly lower in the flexible protocol compared to the fixed protocol (3.4±1.1 vs 5.3±1.8, P<.05). There was no significant difference between the two protocols regarding the number of embryos, implantation rate, clinical pregnancy rate (odds ratio, 0.85; 95% CI, 0.45-1.59) or multiple pregnancy rate (odds ratio, 1.26; 95% CI, 0.45-3.51).

CONCLUSION: Starting the gonadotropin-releasing hormone antagonist according to the size of the leading follicle is as effective as starting on a fixed day and reduces the antagonist administration.