When doing 4D ultrasound, if the baby lies on its back and does not cooperate with the examination, the examination results will not be particularly clear and may produce errors. Therefore, when doing the examination, you should let the baby move around as much as possible to help find the right position, you can gently pat the pregnant woman’s belly, or do fetal education to the fetus, listen to soft music, this can promote the fetal activity, which is conducive to choosing the right position. If this does not work, you can also let the pregnant woman walk downstairs more often so as to promote fetal activity. If the fetus still does not cooperate, you can only make another appointment to do the 4D ultrasound examination again. Before the second examination, you can drink a moderate amount of water or soup to help fill the bladder so that you can see more clearly. Before the ultrasound, you can eat a moderate amount of sweets and chocolate to increase fetal excitement and promote fetal movement so that you can choose the best position for the ultrasound.