Endometriosis affects women in their reproductive years. The exact prevalence of endometriosis is not known, since many women may have the condition and have no endometriosis symptoms. Endometriosis is estimated to affect over one million women (estimates range from 3% to 18% of women) in the United States. It is one of the leading causes of pelvic pain and reasons for laparoscopic surgery and hysterectomy in this country. Estimates suggest that between 20% to 50% of women being treated for infertility have endometriosis, and up to 80% of women with chronic pelvic pain may be affected.

What are endometriosis symptoms?

Most women who have endometriosis, in fact, do not have symptoms. Of those who do experience symptoms, the common endometriosis symptoms are pain (usually pelvic) and infertility. Pelvic pain usually occurs during or just before menstruation and lessens after menstruation. Some women experience painful sexual intercourse (dyspareunia) or cramping during intercourse, and or/pain during bowel movements and/or urination. Even pelvic examination by a doctor can be painful. The pain intensity can change from month to month, and vary greatly among women. Some women experience progressive worsening of symptoms, while others can have resolution of pain without treatment.
Pelvic pain in women with endometriosis depends partly on where the implants of endometriosis are located.

Deeper implants and implants in areas with many pain-sensing nerves may be more likely to produce pain.

The implants may also produce substances that circulate in the bloodstream and cause pain.

Lastly, pain can result when endometriosis implants form scars. There is no relationship between severity of pain and how widespread the endometriosis is (the "stage" of endometriosis).

Other symptoms related to endometriosis include:

lower abdominal pain,

diarrhea and/or constipation,

low back pain,

irregular or heavy menstrual bleeding, or

blood in the urine.

Rare symptoms of endometriosis include chest pain or coughing blood due to endometriosis in the lungs and headache and/or seizures due to endometriosis in the brain.