The endometrial thickness if 10mm depends on the period during which the endometrial thickness is measured. If the endometrium reaches this thickness before menstruation or during ovulation, it is normal. Because the lining of the uterus is not static, it gradually transitions from the proliferative phase to the ovulatory phase after menstruation, and finally reaches the secretory phase, and then the lining of the uterus sheds its blood and the uterine menstruation, which is a complete process, so the lining of the uterus gradually thickens after menstruation. If the endometrium is 10mm thick, it is an abnormal phenomenon if the endometrium is found to be this thick by ultrasound examination at the time of menstruation, mainly because it reaches this thickness at this time. The main reason for this is that such a thick endometrial lining may be caused by inflammation of the endometrial lining, or by a corresponding lesion of the endometrial lining. It should be taken seriously and analyzed in conjunction with the clinical symptoms, and diagnostic curettage can be performed if necessary to clarify the diagnosis and then give treatment.