According to the Advanced Fertility Center of Chicago, the endometrial lining of the uterus is normally around 11.2 millimeters in thickness. An ultrasound measures and evaluates the uterus and the endometrial lining.
The Advanced Fertility Center of Chicago states that anywhere between 8 and 13 millimeters is considered a good level of endometrial lining thickness when it comes to creating and maintaining a viable pregnancy. The lining has the potential to be problematic when it is too thin and measures fewer than 6 millimeters. An endometrial lining with a thickness of 15 millimeters or more has the potential to reduce the likelihood of a successful pregnancy.