Having a 4D ultrasound with the baby lying on its back allows the pregnant woman to roll over from side to side on the examination bed and walk back and forth on the floor, all of which help to change the position of the fetus. Pregnant women go to the hospital for 4D ultrasound with the aim of screening for fetal developmental abnormalities and avoiding the birth of unhealthy babies. However, the baby in the womb may remain lying on its back with no change in position, which can affect the accuracy of the 4D ultrasound. Pregnant women can roll back and forth and get out of bed during the examination the fetal position will change accordingly. In addition, if the fetus is lying still in the womb, pregnant women can listen to soothing music, climb up and down stairs, etc., which can also encourage the fetus to change its position.