Based on the result of the subgroup analysis, there was not any significant difference in Mild OHSS rate between the GnRH antagonist protocols and the Long GnRH agonist protocol (3 studies; 229 women; RR = 0.81, 95% CI: [0.48 to 1.37]; P = 0.44; I2 = 0%; χ2-P = 0.63; very-low quality evidence; Fig. 5). This evidence concerns the gene GNRH1 and ovarian hyperstimulation syndrome.