What causes endometriosis?
Researchers do not yet know the exact causes of endometriosis, but several theories currently exist. The hormone estrogen (highest during childbearing years), is likely to contribute to endometriosis, for example. Other possible causes of endometriosis include:

Blood and lymph systems - Endometrial cells may travel via the bloodstream or lymphatic system to distant places such as the brain and other places far from the pelvis.

Ceolomic metaplasia - The areas lining the pelvic organs have certain cells that can grow into other forms of tissue such as endometrial cells.

Immune system problems - Problems in the immune system may prevent the body from recognizing and destroying cells or tissue that are growing where they should not. Autoimmune endometriosis occurs when the immune system fights off an infection and at the same time attacks healthy cells in the endometrium.

Retrograde menstruation - Menstrual flow that backs up into the fallopian tubes and abdominal cavity can deposit endometrial tissue to strange locations.

Surgery - Endometrial tissues may be directly transferred outside the uterus during surgeries such as episiotomy or Cesarean section.

Risk factors
There are certain risk factors that make it more likely that a woman may develop endometriosis. For example, endometriosis occurs more often in women who have never had children. Women with a mother, sister, or daughter who have had endometriosis also are more likely to be diagnosed with the condition, as are about three quarters of women with chronic pelvic pain. Endometriosis can be influenced by several factors, including:

Cesarean section - Endometriosis may be more likely to develop after cesarean sections, including implants developing in surgical scars and in the urinary tract. Some experts believe endometriosis should be suspected in women with urinary tract symptoms and a history of cesarean section.

Ethnicity - Endometriosis is most common among Asian women, followed by Caucasian women and is reported least frequently in African-American women.

Family history - Some studies report that nearly 7% of first-degree female relatives of women diagnosed with endometriosis also develop it. A family history of endometriosis, especially in a mother or sister, not only puts women at high risk for the condition but possibly a more severe manifestation.

Menstrual problems - Women at higher risk for endometriosis tend to have more problems with menstruation such as a shorter than normal cycle, heavier periods, and longer periods. In fact, many women diagnosed with endometriosis experienced debilitating, painful periods as teens. Heavier, more frequent periods may increase the risk for retrograde menstruation.

Not having children - Some evidence suggests that early pregnancy may prevent endometriosis or relieve symptoms of endometriosis during pregnancy. This may be because dilation of the cervix during labor reduces the risk for retrograde menstruation (menstrual backflow). On the other hand, endometriosis itself can increase the risk for infertility, so it may be a cause rather than a result of not having children.

Uterine abnormalities - Women born with uterine abnormalities that obstruct the normal outflow of blood can cause retrograde menstruation and lead to endometriosis.

Endometriosis can cause mild or severe pain before and during the menstrual period or even lead to infertility. Because endometriosis can have a major impact on quality of life if symptoms interfere with work, relationships, family and overall health, it is important to recognize symptoms of endometriosis early. Continue reading the next section on symptoms of endometriosis to learn more about early symptoms of endometriosis and when to seek medical help.