Newborn babies spitting up may be physiological milk overflow, but also may be caused by diseases, such as congenital hypertrophic pyloric stenosis, intussusception and so on. 1. Physiological milk overflow: newborn babies, because of the imperfect development of various organs, the stomach is horizontal, a large number of food, gastric emptying delay, there may be physiological milk overflow. 2. Congenital hypertrophic pyloric stenosis: Vomiting usually occurs 2~4 weeks after birth, and a small portion occurs 1 week after birth. The first is milk spillage, and then gradually there is projectile vomiting, which gradually develops into vomiting when breastfeeding, and the vomit does not contain bile, but is mostly milk with clots. 3. Intussusception: Acute intussusception is prone to abdominal pain, vomiting and bloody stools, and the vomit contains milk clots, which may be followed by bile. If the baby vomits milk, he should go to the hospital to find out the cause and cooperate with the treatment actively.