GnRH antagonists in ART

The availability of gonadotropin releasing hormone (GnRH) antagonists did not only offer clinicians an alternative to GnRH agonists but, more importantly, has led to the development of new concepts aiming to increase safety and simplicity in ovarian stimulation. These include the modified natural cycle, mild in vitro fertilization (IVF), the use of GnRH agonist for triggering of final oocyte maturation with elective cryopreservation in patients at risk of developing ovarian hyperstimulation syndrome (OHSS), the administration of antagonists during the luteal phase for management of severe OHSS, as well as control of endogenous luteinizing hormone (LH) with GnRH antagonists in intrauterine insemination (IUI) cycles. Administration of GnRH antagonists can be performed by either a single dose or by using a daily scheme. The need to simplify ovarian stimulation led to the development of long-acting follicle stimulating hormone (FSH).