In endometriosis, tissue similar to the endometrium (the uterine lining) grows where it shouldn't — on the ovaries, the tubes, or the pelvic lining. It reacts to the monthly hormone cycle just as the real lining does. This causes inflammation and scarring. The main symptom is periods painful enough to disrupt daily life. It can also cause pain during sex. On the ovary, it can form fluid-filled cysts called endometriomas ("chocolate cysts").
Endometriosis and fertility
The inflammation and scarring can distort the tubes and ovaries, and endometriomas can affect ovarian reserve (the number of eggs left). Many women with endometriosis conceive without help. For others, treatment ranges from laparoscopic (keyhole) surgery to IUI or IVF, depending on how severe it is, age, and egg reserve. Surgery on the ovaries can itself reduce reserve. So whether to have surgery or IVF first is a decision to discuss carefully with your doctor.