Endometriosis ("en-doh-mee-tree-OH-sus") happens when tissue that lines your uterus also grows outside your uterus. These growths often attach to the ovaries or other organs, and they may bleed during your period and cause pain. They may also make it hard for you to get pregnant.
The most common symptoms are pain, bleeding, and trouble getting pregnant. You may have pain in your lower belly, rectum or vagina, or lower back. Some women have heavy periods, bleeding between periods, bleeding after sex, or blood in their urine or stool. Symptoms often are most severe before and during your menstrual period.
Endometriosis can be treated with medicines or with surgery.