The lining of the uterus is usually about 10mm thick at its thickest and should be thinner midway through the postmenstrual period; a 14mm thick lining of the uterine wall three days after menstruation is not normal. The thickness of the endometrium varies at different times in the menstrual cycle. Usually the thickness of the endometrium is thinnest just after menstruation and thickest when menstruation is imminent. After menstruation the endometrium is in the early stage of proliferation, and under the action of estrogen, the endometrium begins to thicken, and at this time the endometrium is thin, about 1 to 2 mm or so, and will not reach 14 mm. If the endometrium is 14mm thick after menstruation, it may be abnormal proliferation of the endometrium, and there is a risk of developing endometrial cancer, so you need to be vigilant, which is not normal. If you find that the endometrium is 14mm thick three days after menstruation, it is recommended that you consult a doctor in time for relevant examinations to clarify the cause of the disease and then treat the cause.