In a systematic review with meta-analysis of RCTs including general IVF patients (unselected for ovarian response or other characteristics), the incidence of any grade of OHSS was significantly lower in GnRH-ant cycles compared to long GnRH-a down-regulation cycles (22 RCTs; OR 0.63, 95% CI 0.50 to 0.81, n = 5,598; I2 = 0%) [84]. The gene discussed is GNRH1; the disease is ovarian hyperstimulation syndrome.