Endometriosis is a chronic condition affecting up to 10% of women between the ages of 15 and 44 in the United States, according to the U.S. Department of Health and Human Services. The uterus is lined with tissue — the endometrium — which is replenished every menstrual cycle to prepare for a fertilized egg. In people who have endometriosis, this tissue grows outside the uterus, and is commonly found on or around the reproductive organs including the fallopian tubes, ovaries, bladder and cervix.