If the purpose of ultrasound is to look at the endometrium, it is better to wait until after the menstruation is clean. If the purpose of ultrasound is to see the endometrium, it is better to wait until after menstruation. If the purpose of ultrasound is to understand the shape of the uterus, or the size of the bilateral adnexa, or if you have abdominal pain and want to know if there is pelvic fluid, then pelvic ultrasound can be done during menstruation. In addition, if you want to have an ultrasound examination of the liver, heart, gallbladder, thyroid and other organs during your menstrual period, there is no effect and it can be done. Pelvic ultrasound is mainly to help diagnose fibroids, endometriosis or uterine malformations, ovarian tumors, inflammatory masses or abscesses in the pelvis. Therefore, it is possible to do a holding ultrasound during menstruation, but a negative ultrasound is not recommended. Although negative ultrasound has the advantages of clear and realistic images, more accurate results, and no need to hold urine during the examination, vaginal ultrasound examination during menstruation increases the risk of infection due to the relaxation of the cervix, which is not good for women’s health.