1. Reasons why babies spit up milk. Babies sometimes spit up milk when feeding. This is because the baby’s digestion is not mature enough and the food cannot be fully digested. At the same time, overeating, improper diet, and eating for too short a time may also be the reasons for the baby to spit up milk. 2. How to prevent babies from spitting up milk. In order to prevent babies from spitting up milk, parents