Newborns spitting up yellow milk may be caused by improper feeding, cold abdomen, congenital digestive malformation and so on. 1. Improper feeding: it may be that frequent breastfeeding or excessive breastfeeding at one time causes the milk to be unable to be digested in a timely manner, which will lead to vomiting, and most of the milk is yellowish, thus leading to vomiting of yellow milk. 2. Abdominal cold: when the newborn’s abdomen is cold, it will easily lead to gastric smooth muscle spasm, so that the stomach contents will be vomited, and accompanied by abdominal pain, diarrhea and other symptoms. 3. Congenital malformations of the digestive tract: pyloric obstruction, for example, can also easily lead to frequent spitting up. Newborns spit up yellow milk, there may be other reasons, it is recommended to go to the hospital in time to improve the examination to clarify the cause of the disease, under the guidance of the doctor to give targeted treatment or treatment.