The inside of the uterus is like a balloon with the front and back walls flat against each other. The pocket is lined with tissue called endometrium. During menstruation the superficial (top) layer of the endometrium is shed. When a woman becomes pregnant, the embryo implants in the endometrium. Injury to and/or infection of the endometrium may damage the lining and cause formation of adhesions (scar tissue) between the inner walls of the uterus where the walls abnormally adhere or stick to each other. Asherman syndrome is a term used to describe adhesions inside the uterus. This scarring can be mild with thin stretchy bands of scar tissue or more severe with formation of thick bands. In the most severe cases, partial or total occlusion or destruction of the inside of the uterine cavity can occur.