Before the 4D ultrasound, you need to choose the right week of pregnancy, do not have an empty stomach, and bring water or food if necessary. Four-dimensional color ultrasound is a combination of ultrasound characteristics and imaging technology, no harm to the human body, non-invasive and without any radiation. At present, it is mainly used to check whether there are malformations of body organs during fetal development, including atrial septal defect, tetralogy of Fallot, cleft lip and palate, hydrocephalus, spina bifida and other diseases. The test is usually performed at 20-24 weeks of pregnancy. On the day of the examination, the patient should not have an empty stomach, otherwise it will affect the movement of the fetus, resulting in some organs not being able to be seen due to the positional factors. If the fetus is in a position for a long time during the 4D ultrasound, which affects the examination results, the fetus can be promoted through activities, eating some food or water for better observation. If you need to have a 4D ultrasound examination, you should go to the hospital in advance to make an appointment. If any abnormality is found, it should be dealt with actively.