The 4D ultrasound examination can satisfy the curiosity of expectant mothers and fathers as well as being one of the most advanced means of monitoring the health of the baby. It can both detect malformations and take portrait photos of the fetus. Through 4D ultrasound, pregnant women can have a general understanding of the development of the fetus in the womb. Previously, ultrasound equipment could only check the physiological indicators of the fetus. Nowadays, 4D ultrasound has a high diagnostic accuracy for malformations and can effectively reduce the birth of malformed babies. Now we will introduce the best time for 4D ultrasound examination. The best time for four-dimensional color ultrasound 1, the first time to check: can be selected at about 14 weeks of pregnancy. In this period, the overall image of the fetus can be displayed on the same surface of the head, body and limbs of the fetus, and in the process of four-dimensional real-time examination, the overall activity of the fetus can be observed to be coordinated or not, but at this time, the fetus face is not well displayed, and the internal organs are not clearly displayed. 2, the second examination: can be carried out at about 22 weeks of pregnancy. At this time, the fetus is enlarged compared with the previous period, and the overall structure of the fetus cannot be shown on the same image, but the local structure and movement status of the fetus are clearer than before, and serious fetal malformations can be found: anencephaly, severe brain expansion, severe open spina bifida, severe pleural wall defect and visceral ectopia, single-chambered heart, and lethal chondrodysplasia. 3.Third examination: it can be carried out around 26 weeks of pregnancy. In this period, the subcutaneous fat of the fetus is fuller than the above, and the facial expression is richer, and the various parts of the fetus are clearer than the previous period, not only is the diagnosis of the above types of malformations more clear, but also the various facial expressions of the fetus, such as eating fingers, yawning, crying, drinking amniotic fluid, and other facial expressions can be seen clearly. Do four-dimensional color ultrasound when the precautions 1, preparation: do four-dimensional color ultrasound whether you need to hold urine depends on the pregnant woman’s pregnancy cycle. When the weeks are small, you need to hold your urine, and when the weeks are big, you don’t need to hold your urine. Generally, you need to hold your urine when you are more than four months pregnant, and you don’t need to hold your urine when you do the four-dimensional ultrasound after the fourth month of pregnancy. 2, check: do four-dimensional ultrasound, pregnant mothers must maintain a good state of mind, the whole process of doing the examination will probably last about 20 minutes, pregnant mothers must be patient. Four-dimensional examination will also be affected by a number of factors, such as maternal obesity, fetal position, amniotic fluid is too small, the placenta and uterine wall and limb and face close, fetal movement is too frequent. Although fetal cardiac anomalies screening technology perfectly fills the gap of routine fetal anomalies screening, its main target is still the severe and fatal fetal cardiac anomalies, and its sensitivity is not good for some minor cardiac anomalies and some malformations that can be treated surgically after birth, such as atrial and small ventricular defects. Therefore, at this stage, even in Europe and the United States, where the technology is most advanced, the diagnosis rate is only 60%. Therefore, it is important not to think that everything will be fine as long as this test is done, and ignore its limitations and the role of other checkups. Finally, to remind the mother to do four-dimensional ultrasound during pregnancy should not be too many times Oh.