"There are several theories that attempt to explain how endometriosis develops. The most popular theory describes retrograde menstruation through the fallopian tubes, with subsequent implantation and growth of endometrial cells contained in the menstrual blood. Other theories involve metaplasia (normal tissue in the abdominal cavity spontaneously changing to endometriosis), direct implantation of endometrial cells into the abdomen during surgery, and spread of endometrial cells from the inside of the uterus to other locations via blood vessels or lymphatics. Each of these may contribute to endometriosis in different patients. Altered immunity may also play a role.
Numerous factors seem to affect whether a woman will have this condition, the severity of the disease in any particular woman, her symptoms, and her response to treatment. These include:
- genetics (an affected sister or mother doubles the risk)
- hormonal status (higher estrogen levels and prolonged heavy menses increases risk)
- lifestyle (low body weight and cigarette smoking reduce risk by decreasing estrogen levels)
- contraceptive use (oral contraceptives possibly reduces progression of disease)
- obstetric history (pregnancy and lactation reduce risk)
- anatomic factors (cervical stenosis increases risk)
- treatment history (prior medical or surgical treatment reduces risk)
- race (Caucasians are at higher risk than african-americans)
- and possibly exposure to environmental toxins, especially those which are estrogenic
Endometriosis is thought to cause infertility by distorting anatomy, creating hormonal abnormalities, altering the pelvic biochemical environment, influencing the immune system, interfering with sperm function, and (possibly) altering the process of embryo implantation."
Source: Women's Surgery Group