A full-term baby’s mouth spitting up bubbles may be caused by respiratory tract infection or mouth ulcers, etc., or it may be caused by physiological factors. There are many reasons for babies to spit up bubbles in their mouths. Respiratory tract infections are mostly suspected when there is fever and coughing, a grunting sound when breathing, and poor milk supply and mental state. There are also cases of pneumonia that manifests itself in spitting bubbles alone. In addition, the baby in the mouth ulcers when the inside of the mouth is uncomfortable will also be through the mouth spitting bubbles to relieve oral discomfort. If the baby has no other symptoms besides spitting up bubbles, it is possible that after eating milk, the milk in the mouth is not swallowed in the mouth to form repeated fermentation of milk bubbles. Full-month baby mouth spitting bubbles may also have other reasons, it is recommended to go to the hospital in a timely manner to improve the examination to clarify the cause of the disease, to give targeted treatment or treatment.