GnRH agonists have been widely accepted in some clinical aspects such as symptomatic endometriosis or leimyomata. Since assisted reproductive technologies have been appeared, GnRH agonists have expanded its clinical usage. Although the flare up effect of agonists has been noted, its application during controlled ovarian hyperstimulation in order to inhibit premature ovulation had been valid without an alternative medication for a long period. Once the GnRH antagonists had been discovered which have been attributed to have no flare up effect with a lower ovarian hyperstimulation syndrome incidence and decrease in requirement of total exogenous gonadotrophin use, it is still controversial whether GnRH antagonists or agonists are more suitable for a optimum ovarian stimulation protocol. In this review, the performance of agonists and antagonists during controlled ovarian hyperstimulation and clinical or ongoing pregnancy rates have been detailed with clinical studies and recent recommendations.
Key Words: GnRH agonist, GnRH antagonist, In vitro fertilization, Assisted reproduction technics, Pregnancy.
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