In the present study, an FSH low dose, step-up protocol was adopted in order to get preferably monofollicular ovulation (with a few cases having two/three preovulatory follicles); all patients having more than three preovulatory follicles were discouraged to conceive: this minimized the risk of multiple pregnancy and ovarian hyperstimulation syndrome even in high-risk patients (e.g. young CC-resistant PCOS patients). The gene discussed is BRD2; the disease is ovarian hyperstimulation syndrome.