The signal of blood flow is visible around the gestational sac. In one case, it is a normal pregnancy, which is required for the growth and development of the early embryo, and the signal of having blood flow occurs when there is a blood supply in the blood vessels around the gestational sac to promote the growth of the embryo. In the other case, when a woman has a small amount of bleeding around the gestational sac, that is, a preterm miscarriage, there will also be a signal of blood flow. When this result is reported, the woman must be alert to see if there is lower abdominal pain or vaginal bleeding, and if there is no abnormality, it is usually necessary to review it regularly. If there is no abnormality, regular review is usually necessary. If there is abnormality such as lower abdominal pain and vaginal bleeding, bed rest and fetus preservation medication should be given to avoid the occurrence of preterm miscarriage or inevitable miscarriage that may affect the growth and development of the embryo.