If we compare GnRH antagonists protocols with GnRH agonist protocols, we find: a) a lower exogenous FSH dose is required for ovarian stimulation due to the natural endogenous FSH’s action during the early follicular phase (40); b) less side effects related to hypoestrogenaemia (41); c) a shorter treatment cycle and reduced FSH consumption; d) lower OHSS incidence of compared to GnRH agonists (42) with a 50% reduction in the relative risk of severe OHSS (43). Here, GNRH1 is linked to ovarian hyperstimulation syndrome.