In the very early stages of pregnancy, around 30 or 40 days, if the ultrasound indicates an echogenic zone in the uterine cavity, most of them are gestational sacs, because at this time the sac has just entered the uterine cavity and the yolk sac has not yet appeared inside the sac, so it will indicate an echogenic zone. If the ultrasound is repeated in a week or so, the yolk sac will usually appear, but there are some women who have an echogenic zone in the uterine cavity that are not pregnant, but may be due to blood accumulation in the uterine cavity or other occupying lesions. Therefore, it is not possible to determine a pregnancy sac simply by the presence of an echogenic zone in the uterine cavity, but also by the menstrual status and the chorionic gonadotropin results, and it is important to review the condition dynamically.