Endometriosis can only occur after menstruation begins in a woman.
Women in their 20s, 30s and 40s are most likely to get endometriosis. The exact cause of endometriosis is unknown. One theory suggests that some of the lining of the uterus during menstruation moves backward through the fallopian tubes into the abdominal cavity, where it attaches and grows. There is also some evidence that the condition may be inherited. Area between the vagina and the rectum An accurate diagnosis of endometriosis must be made by your gynecologist.