Administration of hCG (10.000 or 5.000 IU) is essential in IVF protocols to trigger final oocyte maturation after ovarian stimulation. In high responder patients with potential risk of developing OHSS, hCG is usually withheld and the treatment cycle is cancelled without obtaining (cryopreserved) embryos for replacement.~An alternative approach to trigger final oocyte maturation is to administer a GnRH agonist instead of hCG. This method is not possible following a long GnRH agonist protocol which causes down-regulation of the GnRH receptor. However, following GnRH antagonist treatment the GnRH receptor remains receptive to competitive binding by a GnRH agonist.~It has been well-described in earlier IVF trials that a bolus of GnRH agonist will displace the GnRH antagonist from the GnRH receptors in the pituitary inducing an endogenous LH (and FSH) surge resulting in the maturation of oocytes and good quality embryos. In addition, the risk of moderate-to-severe ovarian hyperstimulation syndrome (OHSS) becomes minimal due to the rapid demise of the corpora lutea. Following luteolysis, fresh embryo transfer would require alternative luteal phase support to secure good clinical outcome. Alternatively, good quality embryos obtained after GnRH agonist triggering can be cryopreserved and replaced in following frozen-thawn embryo transfer (FTET) cycles. Thus, also eliminating late onset OHSS due to pregnancy.
Ovarian hyperstimulation syndrome (OHSS) is a major complication of ovarian stimulation for IVF if hCG is used to trigger final oocyte maturation. The investigators propose that using GnRH agonist as a trigger will eliminate OHSS, even in high-risk patients.