(HealthDay News) -- Endometriosis is a condition in which uterine-like tissue grows outside the uterus. These growths may be referred to as benign tumors, lesions, nodules or implants.

More than 5 million women in the United States have the condition, the National Women's Health Information Center says. The agency says certain factors may place you at higher risk:

• Starting your period at a young age.
• Having heavy periods.
• Periods that last for longer than seven days.
• Short menstrual cycles -- 27 days or less.
• Having a close female relative -- such as a mother, aunt or sister -- with the condition.