If you want to know the condition of the endometrium, it is best to check during ovulation or before menstruation because the relative endometrium is thicker at this time, and through the examination you will be able to know: 1) the thickness of the endometrium; 2) whether the endometrial echogenicity is uniform; 3) whether the endometrial blood flow is normal; and 4) whether there are abnormal echogenic masses in the endometrium, all of which can be understood more clearly through the examination. Vaginal ultrasound can be done in different rooms, without vaginal medication and without douching, to understand the endometrial condition more clearly. In addition, if there are corresponding symptoms, such as irregular vaginal bleeding, infertility or prolonged or increased menstrual periods, endometrial examination is recommended if necessary.