Newborns have bubbles and salivary secretions in their mouths for the following reasons: 1, poor swallowing function in early neonatal period, secretions are not swallowed, poor coordination; 2, feeding is too urgent to meet the amount of milk for the child, poor digestion of the affected child, more saliva secretion, relatively poor swallowing will occur; 3, upper respiratory tract infection symptoms will also appear froth, often accompanied by other symptoms of upper respiratory tract infection,. For example, sneezing, runny nose, etc. But not every child foaming has an infection, parents do not need to be anxious. If the spitting up is really serious, accompanied by spitting up, choking and fever, it is important to seek medical attention.