The first thing you need to do is not to fast, but to do 4D is also a color ultrasound. The main ultrasound during the whole pregnancy is a few times, 12 weeks of pregnancy and 22 weeks of pregnancy, NT at 12 weeks, and the additional 28 weeks at the back, and then the back is mainly to see the situation of amniotic fluid and umbilical cord. Every ultrasound does not require an empty stomach, on the contrary, pregnant women should be told to eat and drink well to come. If you are fasting, sometimes the fetus does not move, and then you cannot see all the organs when you do the ultrasound for detoxification, sometimes you have to tell the pregnant woman to eat for a while during the process, eat something to make the fetus move, and then look at it. So it is not necessary to be fasting to do several dimensions, whether it is 3D, 4D or 2D.