Endometriosis is a painful condition which affects many women during their reproductive lives. It is a serious ailment which can even cause infertility and difficulties in having sex and a baby. Leading obstetrician gynaecologist and author Dr Rishma Dhillon Pai in her book 'Fit at 40' explains the causes symptoms and treatment options of endometriosis. Here's an excerpt from the book. Endometriosis is a gynaecological condition in which cells from the lining of the uterus (endometrium) start growing outside the uterine cavity in the ovaries or around the uterus in the abdominal cavity. These endometrial cells are controlled by female hormones.