Babies who spit up milk while sleeping may have acute gastritis, gastroesophageal reflux, intestinal obstruction, congenital megacolon, and overfeeding. 1. Acute gastritis: various causes of stomach infection, indigestion, spitting up milk when lying down to sleep. 2. Gastroesophageal reflux: most of the anti-reflux defense mechanism is not well developed, spit up when lying down, and the symptoms gradually improve with the increase of age. 3. Intestinal obstruction: the intestinal contents can not pass, food, digestive juices in the intestinal tract stagnation, causing abdominal distension, will also appear spitting up. 4. Congenital megacolon: mostly seen in newborn babies, it will induce stubborn constipation, intestinal obstruction, etc., which is also the cause of spitting up. 5. Overfeeding, etc.: The baby’s stomach is not well developed and is horizontal, so it is easy to inhale air when breastfeeding, breastfeeding a lot, and lying down to sleep can easily cause milk spitting. Baby spit up while sleeping, there may be other reasons, it is recommended to go to the hospital in a timely manner, improve the examination to clarify the cause of the disease, under the guidance of the doctor to give targeted treatment or treatment.