When is it appropriate to do four-dimensional ultrasound?

During pregnancy, it is best to carry out four-dimensional color Doppler ultrasound examination at 20~24 weeks of pregnancy. Four-dimensional color Doppler ultrasound is the most advanced B-ultrasound examination in clinic at present. Through ultrasound, a dynamic image of the fetus in the mother can be observed. At the same time, four-dimensional color Doppler ultrasound is an important basis for identifying whether the fetus has congenital heart disease.