Abstract: Three main purposes of the controlled ovarian stimulation (COS) in assisted reproductive technology (ART) were: to inhibit pituitary activity, to stimulate follicular growth and to induce ovulation. gonadotropin-releasing hormone antagonist (GnRHA) as a competitor of traditional GnRH agonist (GnRHa) inhibits the luteinizing hormone (LH) peak more rapidly, and GnRHA has no GnRHa-related "sudden action" and long-term effect of pituitary down-regulation. In the cycles with GnRHA, the dosage of gonadotropin (Gn) is reduced, the treatment time shorten, and the occurrence of ovarian hyperstimulation syndrome (OHSS) reduced more effectively. In recent years, GnRHA has been widely used in the controlled superovulation (COH) for various types of infertility patients, especially for those specific infertile patients (ovarian low responders, high responders). However, it is necessary to explore whether the new GnRHA protocol can replace the traditional GnRHa long-term protocol, or whether GnRHA protocol can be used as a routine COH protocol. Meanwhile, GnRHA protocol itself should be optimized in future.

Key words: Reproductive techniques, assisted, Ovulation induction, Ovarian hyperstimulation syndrome, Pregnancy outcome, Gonadotropin-releasing hormone antagonist