1. Reasons why babies spit up milk: Babies spitting up milk is a very common phenomenon, and there are many reasons for it. First, the feeding posture may be incorrect, causing the baby to swallow too much or too quickly. Secondly, the baby may suffer from gastrointestinal indigestion and other problems, leading to excessive gastric acidity or indigestion, leading to vomiting. Another situation is that the baby may suffer from diseases such as reflux esophagitis, which can also cause frequent vomiting. 2. How to prevent your baby from spitting up milk. In order to prevent your baby from spitting up milk frequently, we can take the following measures: First, maintain the correct posture and rhythm when feeding. Secondly, you can let your baby burp before feeding.