The thickness of the endometrium is usually between 8 and 13 mm, which is a normal thickness of the endometrium before the onset of menstruation. If it is lower than 8mm, it is more difficult for women of childbearing age to get pregnant. Therefore, if it is less than 8mm, hormonal treatment is usually needed to avoid this infertility. If it is greater than 13mm, it is definitely also possible that it is caused by the constant stimulation of hormone levels, and further treatment is also needed. Therefore, if the endometrium reaches this thickness before the onset of the menstrual cycle, it should be a relatively thin state, but if it is in the secretory phase of the endometrium during the first half of the menstrual cycle, an endometrial thickness of 6mm should also be a normal phenomenon. The endometrial thickness of 8-13 mm is the range during the secretory phase before menstruation.