Many expectant mothers who are eager to see what their baby is doing want to know what the baby's 4D ultrasound looks like when they are pregnant. The third People's Hospital of the city obstetrics and gynecology experts pointed out that different periods of four-dimensional color ultrasound, the picture information is not the same, 22-28 weeks of this best time to take the four-dimensional color ultrasound image is the most clear, the most dynamic, the most memorable value. Fetal head - complete outline, such as defect or deformation is abnormal; The brain line without displacement, no hydrocephalus is normal. The measurement of double parietal diameter of fetal head is an indicator to estimate gestational age and fetal maturity. The average weekly increase in double parietal diameter between 26 and 36 weeks of pregnancy is 0.22 cm. After 36 weeks of pregnancy, the increase rate of double parietal diameter gradually slows down, increasing only 0.1 cm per week. The double parietal diameter of a full-term fetus is between 8 and 10 cm. Double parietal diameter can also predict fetal weight. If the double parietal diameter reaches more than 8.5 cm, the fetus weighs more than 2,500 grams. If the double apex diameter is 9.1-10 cm, the newborn's weight is 3276-3925 grams, and the double apex diameter is greater than 10 cm, the newborn's weight is more than 4000 grams. Fetal heart - Fetal heart exists, strong is normal, weak there are two possibilities, one is that the fetus is sleeping, the other may be abnormal. Normal fetal heart rate is 120-160 beats per minute. Placenta - The normal thickness of the placenta should be between 25 and 50 mm. According to the changes of chorionic membrane, placental spot and basement membrane, placental maturity was divided into four levels: 0, Ⅰ, Ⅱ, Ⅲ. The grading of the placenta indicates its maturity. Normal early pregnancy is mostly manifested as grade 0, which is the growth stage of the placenta. In the middle and late pregnancy, with the maturation of the placenta, it develops from grade I to grade III. After 37 weeks, most placentas are grade III. Therefore, placenta level III can be used as a reference for fetal maturity. Femur length - the length of the fetal femur bone. Its normal value should be less than 20-30 mm different from the double apex diameter value for the corresponding pregnancy month. Amniotic fluid - the depth of amniotic fluid between 3-7 cm is normal, more than 7 cm is increased amniotic fluid, less than 3 cm is reduced amniotic fluid, which is not conducive to fetal growth. Umbilical cord - Normally, the umbilical cord should float in the amniotic fluid, but if an image of the umbilical cord is seen in the neck of the fetus, it may be wrapped around the neck.