The endometrium is the mucosal layer of the uterus in which the fertilized egg attaches. The endometrium, or the uterine lining, located in the innermost part of the uterine wall, is therefore a key factor in successful pregnancy.
Due to a hormonal imbalance in the woman’s body (the dominance of estrogen over progesterone), the uterine lining can grow outside the uterus. This is a disease called endometriosis.