There are many reasons why babies spit up milk, the baby’s stomach is different from the adult’s, it is horizontal, while the adult’s stomach is vertical, the baby’s body is not yet well developed in all functions, the stomach is the same, the baby’s gastrointestinal tract peristalsis is poor, this is also one of the reasons for spitting up milk. The baby’s gastrointestinal tract is already worse than the adult’s, plus it is uncomfortable, so it will spit up milk. There are also reasons for the baby’s mother, such as incorrect maternal breastfeeding posture and nipple inversion, which can cause the child to inhale a lot of air and thus spit up. Then there are some parents who change the baby’s diaper and clothes after the baby drinks milk, and all these drastic movements will make the baby spit up.