Endometriosis is a common cause of infertility and pelvic pain in women. Up to 40% of women having trouble trying to conceive have endometriosis. Endometriosis appears to be more common in daughters of women who had endometriosis, suggesting a genetic link. Endometriosis symptoms include pain during menstruation, intercourse, bowel movements, or emptying the bladder. It is also often present with no symptoms.

Endometriosis occurs when endometrial cells enter the pelvic cavity through a back flow of blood during the menstrual cycle and attach to internal organs. Once in the bloodstream, endometrial cells can travel throughout the body. It is commonly seen on the rectum, ovary, uterus, and tubes but has been documented in many organs distant to the pelvic cavity, including the lungs and the brain.

Endometriosis is typically "staged" according to its severity and likelihood of causing infertility. The stages include: 

• Stage 1 - minimal
• Stage 2 - mild
• Stage 3 - moderate
• Stage 4 - severe