Babies like to sleep on their backs for the following reasons: 1, because the baby was just born, its fetal position in the womb belongs to the abdomen back inward, back outward curled position, due to imperfect bone development, prone to trauma injuries, sleep on their backs is one of the most natural self-protection position, which leads to sleep to increase its sense of security, and is conducive to the development of the nervous system. 2, sleep on their backs is conducive to gastrointestinal Peristalsis and digestion, which can effectively prevent the stomach contents after eating is not easy to reflux into the esophagus, to avoid accidental sucking and choking. 3, lying on his back can promote the development of the baby’s cervical nerves and muscles, thus exercising the neck, chest and other parts of the muscle group, is conducive to head lifting, turning and other large motor exercises.