4D ultrasound is mainly to screen the fetus for malformations, and it is of great significance in the prenatal checkup of the whole pregnancy, and it is also the most comprehensive checkup of the fetus during its growth and development in the womb. Therefore, the items of 4D ultrasound examination are more and more comprehensive than those of other ultrasound examinations during pregnancy. First, the number of fetuses in the uterine cavity and the position of the fetus are examined. The fetus is then examined in detail from head to toe, and all the tissues and organs of the fetus are examined in turn. In general, measurements of the biparietal diameter, head circumference, lateral ventricles, septum cavernosum, cerebellum, posterior cranial fossa, nasal ventral circumference, femur and humerus are required. It is also necessary to show the fetal face, eyes, nose, lips, etc.; to show the complete spinal section; to show the fetal heart in four-chamber cardiac section and right and left ventricular outflow tract section and three-vessel section, etc.; to show the fetal skeleton of the limbs and the section of both hands and feet; to show the fetal liver, stomach, both kidneys, bladder and other internal organs. In addition, in addition to the fetus, examination and measurement of appendages are also necessary. For example, the amniotic fluid should be measured for the maximum dark area and describe the transudation of the amniotic fluid. The placenta should be looked at for the position of attachment and the maturity of the placenta, as well as the insertion of the umbilical cord placenta and the insertion of the abdominal wall. The number of vessels in the cross-section of the umbilical cord is also noted, and the relevant data and fetal heart rate are measured. In addition to the examination of the fetus and appendages, it is also necessary to examine the uterus and adnexal region of the pregnant woman for any obvious abnormalities. However, even though the 4D ultrasound examination is more comprehensive, it has certain limitations and not all types of abnormalities can be screened.