Endometriotic ovarian cysts negatively affect the rate of spontaneous ovulation

A growing body of evidence suggests that ovarian reserve is damaged after excision of ovarian endometriomas. However, it may not be excluded that gonadal damage is at least partly caused by the very presence of an endometrioma per se, thus preceding surgery. To clarify this aspect, we set up a prospective study in women with monolateral endometriomas in order to assess the rate of ovulation in affected ovaries. Seventy women with monolateral endometriomas who had not undergone previous adnexal surgery underwent serial ecographic examinations to determine the side of ovulation. Ovulation occurred in the affected ovary in 22 cases (31%; 95% CI: 22-43%). Assuming that the expected rate of ovulation in both ovaries in healthy women is similar, this difference is statistically significant (P = 0.002). The physiological mechanisms leading to ovulation are deranged in ovaries with endometriomas.