(HealthDay News) -- Endometriosis is a painful condition characterized by uterine tissue that grows outside a woman's uterus.

The U.S. National Women's Health Information Center says warning signs of endometriosis may include:

• Menstrual cramps that are very painful or worsen over time.
• Pain that persists in the pelvic area or lower back.
• Pain in the intestines.
• Pain during or after intercourse.
• Pain while having a bowel movement or urinating while menstruating.
• Bleeding between menstrual cycles.
• Difficulty getting pregnant.
• Feeling fatigued.
• Symptoms during menstruation, such as nausea, bloating, constipation or diarrhea.