Q: How thick should the uterine lining be?

A: The lining of the inside of the uterus is also called 'endometrium.' This is where the embryo implants. A normal uterine lining is necessary in order to conceive and maintain a pregnancy. Two of the qualities of the endometrium or lining, are thickness and appearance. Most doctors feel that the uterine lining should reach a thickness of at least 8-9 mm by the time the eggs have reached maturity (that is, when the ovarian follicles reach at least 18 mm). If it's too thin, your doctor will probably do some tests to find the possible reasons.