GNRH1 and ovarian hyperstimulation syndrome: Specifically considering patients with a diagnosis of PCOS, a recent meta-analysis of 10 RCTs reported that, compared to GnRH agonist protocols, GnRH antagonist protocols are associated with a reduced risk of OHSS overall (OR 0.58, 95% CI 0.44 to 0.77), and specifically of moderate to severe OHSS (OR 0.65, 95% CI 0.51 to 0.82) (44).