Infants who fall asleep and spit up may be related to physiological factors, or may be caused by indigestion, acute gastroenteritis and other reasons. 1. Physiological factors: Because the baby’s stomach appears horizontal, and the cardia sphincter is more flaccid, if the parents do not feed properly, such as feeding too much milk, feeding too fast, or not burping after feeding, immediately let the baby in the lying position to sleep, it may cause spitting up in sleep. 2. Indigestion: Due to the immature development of the infant gastrointestinal system, if the amount of milk fed at one time is too much, it is easy to exceed the digestive capacity of the baby’s gastrointestinal tract, resulting in indigestion, which may result in spitting up in sleep, and may be accompanied by abdominal distension, abdominal pain and other symptoms. 3. Acute gastroenteritis: usually due to the gastrointestinal tract is infected by bacteria, viruses and other pathogenic bacteria caused by the stimulation of pathogenic bacteria, may cause babies fall asleep spit up, may be accompanied by abdominal distension, diarrhea and other manifestations. The baby fell asleep and spit up, there may be other reasons, it is recommended to go to the hospital, improve the examination to clarify the cause of the disease, under the guidance of the doctor to give targeted treatment or treatment.