Girls and boys are all the same. Compared with other ultrasound examinations, four-dimensional ultrasound can observe the dynamic movement of internal organs in real time and accurately distinguish the sex of the fetus. Although four-dimensional color Doppler ultrasound can clearly see the sex of the fetus, in order to avoid exposing the sex of the fetus during the examination, doctors will take the initiative to avoid the sex characteristics and lower body of the fetus.