Is the flexible GnRH antagonist protocol better suited for fresh eSET cycles?

This study was performed to evaluate the efficacy of the flexible GnRH antagonist protocol in comparison with the long GnRH agonist protocol in elective single embryo transfer (eSET) practice. It was conducted in a publicly funded in vitro fertilization program.

We performed a prospective cohort analysis of data from a private infertility clinic from August 2010 to August 2011. Three hundred fourteen women with normal ovarian reserve and undergoing fresh eSET cycles were included. Sixty-four women underwent follicular stimulation using a flexible GnRH antagonist protocol, and 250 underwent stimulation with a standard long mid-luteal GnRH agonist protocol.

Implantation rates (35.9% in the GnRH antagonist group and 29.6% in the GnRH agonist group, P = 0.5) and ongoing pregnancy rates (32.8% in the GnRH antagonist group and 28.8% in the GnRH agonist group, P = 0.5) were equivalent in both groups. The duration of stimulation (9.8 ± 2 days vs. 10.7 ± 1.8 days, P < 0.001) and total FSH dose required (2044 vs. 2775 IU, P < 0.001) were lower in the GnRH antagonist group than in the GnRH agonist group. The number of mature oocytes (6.0 vs. 10.0, P < 0. 001) and number of embryos (5.0 vs. 7.0, P < 0.001) were also lower in GnRH antagonist group. However, the number of embryos cryopreserved was similar in both groups (median 2.0, P = 0.3).

In women undergoing in vitro fertilization, the flexible GnRH antagonist protocol yields implantation and ongoing pregnancy rates that are similar to the long GnRH agonist protocol, and requires lower doses of gonadotropins and a shorter duration of treatment. The flexible GnRH antagonist protocol appears to be the protocol of choice for an eSET IVF program.