[Biological assessment criteria during antagonist protocols].

Until recently, gonadotropin-releasing hormone (GnRH) agonists were the only choice available to physicians for prevention of premature luteinizing hormone (LH) surges in women undergoing controlled ovarian stimulation. The recent approval of GnRH antagonists for this indication gives clinicians some new options. In several trials performed, the GnRH antagonist regimens have been associated with a slightly lower pregnancy and implantation rates than the established GnRH agonist protocols. This review summarizes the main studies concerning oocyte quality and fertilization in IVF cycles with GnRH antagonists. As a result, there is no difference between GnRH agonist and GnRH antagonists concerning oocyte maturation and fertilization rates. There are very few data about the incidence of oocyte morphology anomalies in IVF cycles with antagonists.