A subsequent large, well-designed RCT randomised 1,050 infertile women to GnRH antagonist or GnRH agonist protocols in their first IVF cycle with an hCG trigger in all but 3 cases, and confirmed a significant reduction in the rate of severe and moderate OHSS (5.1% vs 8.9% and 10.2% vs 15.6% respectively) when an antagonist cycle was used, with no difference in subsequent live birth rates (22). Here, GNRH1 is linked to ovarian hyperstimulation syndrome.