In a meta-analysis of 7 RCTs, Xiao et al. [108] showed that the rate of OHSS was significantly lower in the GnRH antagonist group than the GnRH agonist group in women with PCOS (odds ratio 0.36, 95% confidence interval 0.25–0.52). This evidence concerns the gene GNRH1 and polycystic ovary syndrome.