It can be said that 4D ultrasound is not harmful to human body because ultrasound does not produce ionizing radiation, and the most important effect is thermal effect. Ultrasound for diagnosis, including 4D ultrasound, has extremely low thermal effect, and the output energy is generally strictly limited and controlled within the safe range, so there is no harm to adults under normal use. When applying 4D ultrasound to examine the fetus, there is no problem as long as long-term and continuous scanning of certain parts of the fetus, such as the fetus’ eyes and genitals, is avoided.