4D ultrasound is the most advanced color ultrasound equipment, which can truly record the dynamics of the fetus. Four-dimensional ultrasound is a kind of examination for screening fetal malformations that pregnant women go to the hospital around 21 weeks to 24 weeks. Generally, the values reported in the four-dimensional ultrasound include: biparietal diameter, head circumference, abdominal circumference, femur length, humerus length, umbilical cord blood flow ratio, fetal position, amniotic fluid index, amniotic fluid dark area, ultrasound gestational week, the number of fetuses, and the presence of any obvious abnormality. Through these values the doctor will comprehensively assess the fetal development, the conclusion of the report will describe whether the examined area is normal or not, no obvious abnormality or difficult to determine the ultrasound report will recommend the patient to do other tests to clarify the diagnosis. In order to understand the development of the fetus, can the fetal head is intact, biparietal diameter data and gestational weeks in line with whether; fetal heart rate should be around 120 to 160 beats per minute; amniotic fluid volume is normal and so on. Pregnant women cooperate with the doctor to do a good job of pregnancy checkup instructions, any discomfort during pregnancy, such as abdominal pain or vaginal bleeding or examination of various data have abnormalities, you need to go to the hospital in a timely manner.