The endometrium actually changes significantly throughout the menstrual cycle, and the thickness of the endometrium varies at different times. For example, in the first half of the menstrual cycle, the thickness of the endometrium reaches 5 mm or more, which is relatively normal and does not affect conception, but it also depends on the situation. The endometrium is divided into three different stages: early hyperplasia, mid-proliferation and late hyperplasia. If the endometrium is detected in the early stage of hyperplasia, the thickness of the uterus is about 5 mm, which is relatively normal, so there is no need to worry too much. However, if the thickness of the uterus is about 5 mm in the middle or late stage of hyperplasia, it should be taken seriously as it may be caused by a thin endometrium. The thickness of the endometrium is about 4-6 mm in the early stage of hyperplasia, and gradually increases to 8-10 mm in the middle stage of hyperplasia, and increases to 9-10 mm in the late stage of hyperplasia. If the endometrium is 5 mm in the early stage of hyperplasia, it is normal and there is no need to worry, but if it is the other two stages, you should be checked as soon as possible.