Surgical confirmation of severe ovarian endometriosis, stage III–IV endometriosis according to rASRM; age ≤ 40 year; regular menstrual cycle (25–35 day per cycle) in the prior 3 month; antral follicle count more than 4 and less than 20 on menstrual cycle day 2–3; basal serum FSH ≤10 IU/L. Here, BRD2 is linked to ovarian endometriosis.