Nine-month-old babies like to sleep on their stomachs, if there is no other physical discomfort is a normal phenomenon, if there is digestive discomfort, snot, etc., is not normal. Sleeping on the stomach is usually a comfortable sleeping position, and most nine-month-old babies sleeping on their stomachs are a normal phenomenon. When in the mother’s body, the baby’s position is curled up, sleeping on the stomach is similar to the position in the mother’s body, which can give the baby a sense of security. If there is no other discomfort, parents can rest assured. However, some babies have nasal congestion and other conditions, sleeping on their stomachs is conducive to preventing the backflow of nasal mucus, which indicates that the child has an upper respiratory tract infection. There are also some babies with abdominal pain and other indigestion, sleeping on the stomach can relieve pain, the baby also like to sleep on the stomach. If the baby likes to sleep on his back, parents should actively pay attention to, when there is discomfort, we should consult a doctor in time, for appropriate intervention.