There are several possibilities for babies to spit up when they fall asleep: improper feeding, congenital digestive disorders, and gastroesophageal reflux. 1. Improper feeding: it may be due to the pregnant mother in the child before bed, a single feeding too much, immediately after feeding the baby to sleep, and did not give the baby to do burping exercise, easy to flatulence, leading to the child’s stomach bloating and spit up in bed. 2. Congenital digestive diseases: for example, the common congenital megacolon, the baby often manifests constipation, abdominal distension, spitting up, the child’s weight does not increase, poor appetite, and even caused by low intestinal obstruction; can also be seen in the pyloric obstruction, pyloric obstruction of children prone to delayed gastric emptying, resulting in the accumulation of excessive gastric contents, increased intragastric pressure, and spitting up. 3. esophageal reflux: due to the child, the digestive organs are not fully developed, the esophageal sphincter strength is insufficient, and when the child is cold and flatulence, it is easy to spit up. There are many other reasons for babies to spit up, if similar symptoms occur, it is recommended to go to the hospital as soon as possible to avoid delays.