Endometriosis and infertility: is there a cause and effect relationship?

An association between endometriosis and infertility has long been noted. Endometriosis affects approximately 5% of the general population. In infertile women, the prevalence may be as high as 30%. Multiple studies, the majority of which are retrospective, indicate that the monthly fecundity of patients with endometriosis may be decreased by half compared to women without the disease. The precise cause-effect relationship between endometriosis and infertility remains controversial. In advanced cases of endometriosis, with distorted pelvic anatomy, the mechanism of infertility is more easily explained. Recent evidence suggests that treatment of early-stage endometriosis may increase pregnancy rates. Many etiologies of infertility in early-stage endometriosis have been proposed. These include endocrine dysfunctions such as luteal phase defect and luteinized unruptured follicle syndrome. In the last 15 years, alterations in the local pelvic immune environment have been the subject of multiple basic science investigations. Unfortunately, there is no satisfactory hypothesis that unequivocally explains the association of early stages of endometriosis with infertility.