Uterine lining thickness chart

As one can see in this chart, the thickness of the uterine lining changes throughout the menstrual cycle.

Days 0-14 of the menstrual cycle

During this timeframe, the uterus is in the proliferative phase. Estrogen induces growth of the functional layer of the endometrial lining, which enables it to grow from about 1-3 mm post cycle to 6-8 mm approximately.

Days 12-16 of the menstrual cycle

At this point, the endometrial layer is about 6-8 mm thick. Ovulation occurs during this phase—an egg is ejected from the ovaries and begins making its way down the Fallopian tubes into the womb.

Days 14-28 of the menstrual cycle

By day 28 of the cycle, the endometrium measures between 10-16 mm. The ovaries are in the luteal phase and the uterus in the secretory phase. LH induces the formation of the corpus luteum, which degenerates if pregnancy doesn't occur. The endometrium is shed if no embryo implants.