The best time for the second 4D ultrasound is between 22-26 weeks of gestation, mainly to screen the fetus for developmental abnormalities. Usually, the fetal anatomy is already formed at this time, and the amniotic fluid volume is moderate, so the 4D ultrasound shows clear and easy to observe images, which makes it easy to accurately screen for important fetal abnormalities. During the second 4D ultrasound examination, the fetal length is first evaluated and the development is estimated to be in accordance with the gestational week. Secondly, the fetus is observed one by one for malformations such as cleft lip and palate, spina bifida, and whether the brain, heart, kidneys and other important organs are developing normally. Finally, we will observe whether the placenta position, umbilical cord position and amniotic fluid volume are normal. If the fetus is poorly positioned or the limbs are obscured to the face during 4D ultrasound examination, which is not conducive to observation, the pregnant woman need not worry too much, she can take a walk, climb stairs and other activities to promote the fetus to move in the uterus and change its position, and then review the test again. If the test result shows that the fetus may have malformation, such as fetal facial malformation, digestive system malformation, etc., then it should be treated accordingly under the guidance of the doctor.