Ovarian Endometrioma

Guidelines for Selection of Cases for Surgical Treatment or Expectant Management

Molly Carnahan; Jennifer Fedor; Ashok Agarwal; Sajal Gupta


Expert Rev of Obstet Gynecol. 2013;8(1):29-55. 

In This Article

Mechanism & Effects of Ovarian Endometrioma on Fertility

The exact mechanism by which ovarian endometrioma causes infertility is unknown. In cases of severe endometriosis, infertility is associated with adhesions, tubal blockage and anatomical distortion. Milingos et al. reported that women with ovarian endometriomas might have infertility associated with chronic pelvic pain, and therefore dyspareunia.[38] However, for women without pelvic pain or anatomical distortions, endometrioma infertility is potentially associated with a decreased oocyte retrieval rate, reduced oocyte quality and reduced embryo quality.

In a recent retrospective case–control study, the AFC and number of oocytes retrieved was not significantly different between the affected and contralateral healthy ovary, and the total number of retrieved oocytes did not differ from that of a control group of women undergoing IVF (Table 1).[40] However, most studies are not in agreement with these findings. In a meta-analysis of two studies by Gupta et al., significantly fewer follicles were found following stimulation in women with endometriomas as compared with a control group (weighted mean difference [WMD]: -0.88; 95% CI: -1.43 to -0.32). Furthermore, in a meta-analysis of five studies, fewer oocytes were retrieved in women with ovarian endometriomas compared with women without endometriomas (WMD: -0.74; 95% CI: -3.16, -0.23).[40] The finding that the number of aspirated oocytes is reduced is supported by a recent histological study in women under the age of 35 years, in which ovarian tissue adjacent to the ovarian endometrioma cysts had one- to two-thirds fewer follicles compared with ovarian tissue adjacent to other benign ovarian cysts.[41] Kitajima et al. attributed this decrease in follicle count to a mechanism other than mechanical stretching of the ovarian cortex, and suggested that the inflammatory response led to fibrosis in normal ovarian cortex.[42] In support of this finding, Matsuzaki et al. found that levels of oxidative stress were higher in women with endometriomas in the surrounding normal ovarian tissue than in women with other benign ovarian cysts.[43] Zhang et al. reported that in vitro oxidative stress induced apoptosis in oocytes and necrosis in early follicles,[44] which supports the theory that endometrioma damage to the follicles is caused by oxidative stress. Oxidative stress is a potential cause of necrosis in an ovary with endometrioma and reduced follicular density.[42] Kuroda et al. report that in women over 35 years, the number of follicles in adjacent ovarian tissue is not significantly different between women with ovarian endometrioma cysts and women with benign ovarian cysts. This finding suggests that the reduction in follicles found in women below 35 years of age with ovarian endometriomas, but not in women with other benign ovarian cysts, may be a protective mechanism in ovarian endometriosis for the adjacent tissue or may be a selection of age-resistant follicles.[41]

The effect of ovarian endometriomas on oocyte quality is controversial and difficult to assess. Kumbak et al. found women with ovarian endometriomas had a significantly fewer number of oocytes retrieved compared with women with simple, basal ovarian cysts, but the number of mature oocytes retrieved and the fertilization rate were not significantly different between the groups.[19] However, other researchers have found decreased oocyte quality with fewer mature oocytes retrieved in women with endometriosis compared with women undergoing IVF for male factor infertility.[25] Kumbak et al. reported a significantly reduced implantation rate, which is in agreement with other studies.[19]

Oocyte donation studies provide the best evidence for the negative effect of endometriosis on oocyte quality. In one study, oocyte donations from women without endometriosis were not associated with significantly different IVF outcomes in terms of implantation and pregnancy rate when compared with women without endometriosis. However, donated oocytes from women with endometriosis had significantly lower implantation rates, but not pregnancy rates.[45] Furthermore, oxidative stress may occur early in endometrioma patients, and cyst removal does not improve oocyte quality, which may explain why many studies have not shown improvements in IVF outcomes after laparoscopic removal of ovarian endometriomas (see section on 'Expectant management' and Table 1 & Table 4).[43]

Embryo quality is another important determinant in IVF success. Bongioanni et al. found significantly higher cancellation rates due to a poor response in women with in situ endometriomas and prior surgery for ovarian endometriomas compared with women with tubal factor infertility, but there was no significant difference in the live birth rate in those who did not cancel. A poor response is associated with fewer follicles. Reinblatt et al. found that women with bilateral endometriomas did not differ from women with tubal or male factor infertility with regard to IVF outcome measures of AFC, number of oocytes retrieved, fertilization rate, cleavage rate, number of embryos transferred and percentage of good embryos transferred – this suggests that embryo quality is not negatively impaired in women with endometriomas.[46] The results from a study by Barri et al. agree with this finding in that the number of embryos available for transfer and the number of embryos that were frozen were significantly lower in the women with endometriomas, but the reduction was due to fewer oocytes retrieved. In addition, the live birth rate was not significantly different.[29]

Overall, how ovarian endometrioma causes infertility is not well understood, and recent research suggests that ovarian endometrioma infertility is associated with reduced oocyte quantity and quality, but not embryo quality. Understanding how ovarian endometriomas affect fertility can help improve surgical treatments, fertility preservation techniques and IVF protocols.