Endometriosis is when the tissue that makes up the uterine lining (the lining of the womb) is present on other organs inside your body. Endometriosis is usually found in the lower abdomen, or pelvis, but can appear anywhere in the body. Women with endometriosis often have lower abdominal pain, pain with periods, or pain with sexual intercourse, and may report having a hard time getting pregnant. On the other hand, some women with endometriosis may not have any symptoms at all.
Endometriosis is estimated to affect between 3% and 10% of reproductive-aged women. Endometriosis can only be truly diagnosed by a doctor performing a laparoscopy (a surgery where a doctor looks in the abdomen with a camera usually through the belly button) and taking a sample of a suspected abnormality. Thus, the proportion of women affected by endometriosis differs among women having surgery for different reasons. In women without symptoms who are having surgery for elective sterilization (having their tubes tied), 1-7% will actually have endometriosis diagnosed at the time of their surgery, as will 12-32% of women having surgery for pelvic pain, and 9-50% of women having surgery for infertility. Endometriosis is rarely found in girls before they start their period, but it is found in up to half of young girls and teens with pelvic pain and painful periods.