Endometriosis occurs when cells from the lining of your womb (uterus) grow in other areas of your body. This can cause pain, heavy bleeding, bleeding between periods, and problems getting pregnant (infertility).
Every month, a woman's ovaries produce hormones that tell the cells lining the uterus to swell and get thicker. Your uterus sheds these cells along with blood and tissue through your vagina when you have your period.
Endometriosis occurs when these cells grow outside the uterus in other parts of your body. This tissue may attach on your:
It can grow in other areas of the body, too.