The baby can lie down moderately one to two weeks after birth. One to two weeks later, as the baby gradually adapted to the outside world, you can properly lie on your back to train the strength of the head up and the upper limbs, just started thirty seconds each time, three or four times a day, if the child does not cooperate, there is no need to force, you can change the time and try again. When three months, if the neurological development is sound, most babies will be able to lie on their backs with their heads raised 90 °. Lying on the stomach is also an effective means of relieving colic and bloating, in which case the child’s discomfort is reduced. Parents should guard the side when lying down and not leave to avoid suffocation. If the child is unable to hold his head up steadily while lying on his back at three months, or if he is still unable to crawl at eight or nine months, he needs to be evaluated by a pediatrician.