DefinitionEndometriosis is a condition in which the tissue that behaves like the cells lining the uterus (endometrium) grows in other areas of the body, causing pain, irregular bleeding, and possible infertility.The tissue growth (implant) typically occurs in the pelvic area, outside of the uterus, on the ovaries, bowel, rectum, bladder, and the delicate lining of the pelvis. However, the implants can occur in other areas of the body, too.Causes, incidence, and risk factorsEach month a woman's ovaries produce hormones that stimulate the cells of the uterine lining (endometrium) to multiply and prepare for a fertilized egg. The lining swells and gets thicker.If these cells (called endometrial cells) grow outside the uterus, endometriosis results. Unlike cells normally found in the uterus th