How many times do I need to do four-dimensional ultrasound?

After pregnancy, do four-dimensional color Doppler ultrasound once, but if the first time do four-dimensional color Doppler ultrasound does not pass, may need to do a second four-dimensional color Doppler ultrasound to make a diagnosis. Generally in pregnancy there are 24-28 weeks of time, you can go to the hospital to do four-dimensional color Doppler ultrasound examination, understand that the fetus in utero development has no abnormal phenomenon. Before doing four-dimensional color Doppler ultrasound, try to eat something, so that the fetus can be more active in the uterus, do four-dimensional color Doppler ultrasound examination is also easy to pass through at one time. Some women in four-dimensional color Doppler ultrasound, because the fetal position is not good so it is not easy to pass through at one time, this time can also get out of bed for activities, climb stairs, communicate with the fetus, let the fetus change position in the uterus, then go back to the hospital for examination, try to be able to pass through the examination at one time.