And just as the cells inside the uterus swell and are shed each month, these misplaced cells do exactly the same thing. They swell and bleed, causing pain and infertility. More than 5 million women in North America have been diagnosed with endometriosis, which is about 10 percent of women in their reproductive years. It runs in families to a degree, but genetic factors are not strong. If you have endometriosis, there is about a four to five percent chance that your mother or a sister will also have had it.
Endometriosis starts with cells that are wandering in the wrong direction.
Normally, the uterine lining cells pass downward and out of the body during menstruation. But sometimes these cells slip through the fallopian tubes that lead to the abdominal cavity. From there, they can end up virtually anywhere. If they somehow evade your immune defenses and attach in your abdominal cavity, the result is endometriosis. Occasional microscopic clumps occur in women with no symptoms at all.