(HealthDay News) -- Endometriosis occurs in women when endometrial tissue that lines the uterus grows outside of the uterus. Pelvic pain during menstruation is a common symptom.

The womenshealth.gov website says risk factors for endometriosis include:

  • Never having had a child.
  • Having a menstrual period of longer than seven days.
  • Having a menstrual cycle of fewer than 27 days.
  • Having a close family member who has had endometriosis.
  • Having a health condition affecting the normal flow of menstrual blood.
  • Having had an infection that damaged cells in the pelvis.