Endometriotic ovarian cysts do not negatively affect the rate of spontaneous ovulation

Study question: Do endometriotic ovarian cysts influence the rate of spontaneous ovulation? Summary answer: Endometriotic cysts, no matter what their volume, do not influence the rate of spontaneous ovulation in the affected ovary. What is known already: Endometriotic ovarian cysts may negatively affect spontaneous ovulation in the affected ovary. Study design, size, duration: This was a prospective observational study performed between September 2009 and June 2013. Participants/materials, setting, methods: This study included women of reproductive age with regular menstrual cycles and unilateral ovarian endometriomas (diameter≥20 mm)desiring to conceive. Exclusion criteria were: hormonal therapies in the 3 months prior to study entry and previous adnexal surgery. Patients underwent serial transvaginal ultrasound to assess the side of ovulation (for up to six cycles). Main results and the role of chance: Ovulation was monitored in 1199 cycles in 244 women (age, mean±SD, 34.3±4.9 years). 55.3% of the patients had left endometriomas and 44.7% had right endometriomas (P = 0.024). The mean (±SD) diameter of the endometriomas was 5.3 cm (±1.7 cm). Ultrasonographically documented ovulation occurred in 596 cycles in the healthy ovary (49.7%; 95% CI, 46.8-52.6%) and in 603 cycles in the affected ovary (50.3%; 95% CI, 47.1-53.2%; P = 0.919). This observation was confirmed in patients with diameter of the cyst ≥4 cm(n = 166) and in those with diameter of the cyst ≥6 cm(n = 45). One hundred and five patients spontaneously conceived (43.0%; 95% CI, 36.7-49.5%). Limitations, reason for caution: The high pregnancy rate reported in this study wasobserved in a selected population of women with endometriomas and cannot be extrapolated to all patients with endometriosis. Wider implications of the findings: Since ovarian endometriomas do not impair spontaneous ovulation, the impact on fertility of surgical excision of ovarian endometriomas should be further investigated.