This is due to the poor fetal position, the face of the fetus facing backwards, or the small amount of amniotic fluid in front of the face, and the obstruction of the fetal limbs, umbilical cord, placenta and uterine wall. If the mother-to-be does not cooperate with her baby, she can’t do anything for a while. It is recommended that the mother-to-be can go out and move around a little to drive the fetus and change its position. This way, the 4D can be done more clearly and check the growth and development of the fetus. Since 4D ultrasound is a dynamic three-dimensional display, it can observe the fetus’ activity in the mother’s body and can directly display surface abnormalities of the fetus, such as cleft lip, cleft palate and abnormal bone development. The equipment required to do prenatal ultrasound is high. The 4D ultrasound machine is a high-end equipment, which is also very different from the previous black and white B ultrasound equipment, the 4D ultrasound charges vary from place to place, generally around 300 yuan.