Substituting HCG with GnRH agonist to trigger final follicular maturation--a retrospective comparison of three different ovarian stimulation protocols

The study retrospectively evaluated the influence of triggering final oocyte maturation with gonadotrophin-releasing hormone (GnRH) agonist on the outcome of IVF cycles. Four hundred and sixty consecutive women admitted to the IVF unit during a 4-year period were enrolled in the study. Ovarian stimulation characteristics and clinical pregnancy rate were compared between three groups: patients at risk of developing ovarian hyperstimulation syndrome (OHSS), undergoing either the long GnRH-agonist protocol (agonist group) or the flexible multidose GnRH-antagonist protocol who received GnRH-agonist for final oocyte maturation (antagonist-agonist group); and patients not at risk of developing severe OHSS undergoing the flexible multidose GnRH-antagonist protocol who received human chorionic gonadotrophin (HCG) for final oocyte maturation (antagonist-HCG group). Implantation and clinical pregnancy rates were lowest in the antagonist-agonist group despite the fact that no difference were was observed in fertilization rates between the groups. Moreover, the high-responder antagonist-agonist group required shorter stimulation and had higher numbers of oocytes retrieved as compared with the high-responder agonist-group. No case of severe OHSS was observed in the antagonist-agonist group. The use of flexible multidose GnRH-antagonist protocol with GnRH-agonist for final oocyte maturation, in high-responder patients, eliminates the risk of OHSS but results in decreased implantation and pregnancy rates.