4D ultrasound is currently the world’s most advanced ultrasound equipment, which is a three-dimensional dynamic continuous, intuitively speaking, video. Based on the ordinary color ultrasound, it is able to observe the immediate changes of the fetus in the uterine cavity like a three-dimensional photo, such as the movement of the limbs and the beating of the heart, all of which can be clearly seen. 4D ultrasound is performed between 20-28 weeks of pregnancy, when the fetal limbs are small and the amniotic fluid is large. It can clearly see the entire fetal body development and provide an accurate scientific basis for early diagnosis of congenital body malformations and congenital heart diseases, such as whether there is cleft lip and palate, hydrocephalus, spina bifida, microcephaly, anencephaly, cerebrospinal bulge, visceral ectopia, intestinal atresia, megacolon, skeletal deformity, short limb deformity, etc. It can also see if there is contamination of the amniotic fluid, the position of the placenta, and if the umbilical cord has wrapped around the neck.