1. What is the reason why babies spit up milk? Babies spitting up milk refers to the reflux of milk from the stomach into the esophagus and mouth after feeding. It often occurs in newborns and infants. There are many reasons for this, including underdeveloped digestion, incorrect feeding posture, overfeeding, etc. 2. Immature digestion: The digestion of newborns is very immature, and the gastrointestinal tract is not yet fully mature. This means they are prone to vomiting. In addition, the esophageal sphincter is not yet developed