Endometriosis occurs when the tissue which is similar to the lining in the uterus grows outside of the uterus. It’s not clear exactly what causes Endometriosis; however, researchers are looking up probable causes which include: - Issues with menstrual period flow Research has shown that retrograde menstrual flow is one of the most likely causes of endometriosis. This is due to the tissue shedding during the period flow which moves through the fallopian tubes into the other areas of the body, including the pelvis. - Genetic factors Endometriosis runs in the family, meaning it could be inherited throughout the generations. - Immune system issues An immune system that does not work correctly can fail to find and destroy the endometrial tissue that grows outside of the uterus. Certain cancers and immune system disorders are more commonly found in women with endometriosis. - Hormones Estrogen hormone is what appears to promote endometriosis. Researchers are reviewing whether endometriosis is an actual issue with the body’s hormone system. - Surgery In surgeries to an abdominal area like a c-section, or a hysterectomy, the endometrial tissue could be accidentally picked up and moved.