Now let's talk about endometriosis.
The lining of the uterus is made up of special cells, called endometrial cells. This lining builds up, getting ready for a possible pregnancy. If a fertilized egg does not implant in the thickened lining of the uterus, it is shed during your period. This endometrial lining usually only grows inside the uterus. When the endometrial cells grow outside the uterus, this is called endometriosis. Sometimes, the endometrial cells grow on the ovaries or fallopian tubes; they can even grow on the bladder or intestines.
The cells can cover a small area or a large area, and they may be in more than one place. No matter where the cells grow, they can still bleed, just like they do in the uterus. These cells can cause problems, even if they don't bleed. The two most common problems are pain and not being able to get pregnant.
The amount of pain or problems you experience isn't necessarily related to the size or number of endometrial growths that you have. Some women have a few small areas of endometriosis, but have a great deal of pain, while others have many large areas and only a few symptoms.
Endometriosis can get worse over time, but in which women this will happen, no one can tell. This is because doctors are not yet sure how it grows. Women who are more likely to have endometriosis often have other women in their family who have it too, like a mother or sister.