Why does surgery for endometriosis-associated infertility often fail to improve pregnancy outcome?

Endometriosis can impair natural reproduction through multiple mechanisms, including distortion of pelvic anatomy and chronic peritoneal inflammation. On this basis, surgical treatment might be reasonably expected to benefit. However, clinical evidence challenges this belief. Surgery can indeed improve natural reproduction, but real benefits are modest. The reasons for the disappointing efficacy of surgery are discussed in this review. They include the presence of 'microscopic' endometriosis, the co-occurrence of other undetected causes of infertility, the rapid reoccurrence of adhesions, the inability of surgery to interfere with underlying pathogenetic mechanisms, the frequent recurrence of endometriotic lesions, and the association with other gynecological conditions that cannot be effectively treated with surgery (such as adenomyosis). On the other hand, the frequently discussed ovarian reserve injury may not be a determining factor (even if of utmost relevance for ART), and the strength of the evidence linking superficial peritoneal disease, ovarian endometriomas, and deep endometriosis to infertility is rather debatable. In conclusion, surgery for infertile women with endometriosis remains an option, but it cannot intrinsically ensure high rates of reproductive success. Realistic and comprehensive information on safety, effectiveness, and alternatives must be given for valid shared decision-making.