Use of GnRH antagonists in patients with an a priori poor IVF prognosis results in predictably poor outcomes. Patients without factors predicting poor outcome have acceptable PRs. The pattern of E2 rise immediately after initiation of GnRH antagonists does not predict cycle outcome. Oral contraceptives can be successfully used to schedule antagonist-based IVF cycles but might increase the risk of cycle cancellation in some patient populations.

Shapiro, D. B., Mitchell-Leef, D., Carter, M., & Nagy, Z. P. (2005). Ganirelix acetate use in normal-and poor-prognosis patients and the impact of estradiol patterns. Fertility and sterility, 83(3), 666-670.

Elevated estradiol (E(2)) levels predispose to development of ovarian hyperstimulation syndrome (OHSS). Since GnRH antagonist is associated with a reduction in E(2) levels, we hypothesized that GnRH-antagonist treatment of women down-regulated with GnRH agonist who are at risk of OHSS might reduce E(2) levels and avoid cycle cancellation.

Gustofson, R. L., Segars, J. H., & Larsen, F. W. (2006). Ganirelix acetate causes a rapid reduction in estradiol levels without adversely affecting oocyte maturation in women pretreated with leuprolide acetate who are at risk of ovarian hyperstimulation syndrome. Human Reproduction, 21(11), 2830-2837.

Ganirelix is effective, safe, and well tolerated. Compared with leuprolide acetate, ganirelix therapy has a shorter duration and fewer injections but produces a similar pregnancy rate.

Fluker, M., Grifo, J., Leader, A., Levy, M., Meldrum, D., Muasher, S. J., ... & Shapiro, D. B. (2001). Efficacy and safety of ganirelix acetate versus leuprolide acetate in women undergoing controlled ovarian hyperstimulation. Fertility and sterility, 75(1), 38-45.