If a newborn suddenly spits up a lot of milk, the following causes should be considered. First of all, it is caused by acute gastroenteritis. If the newborn has a viral or bacterial infection, it will cause acute gastroenteritis and the newborn will have a lot of vomiting and diarrhea. In this case, the newborn should be given timely stool and blood tests, and if it is caused by a serious bacterial infection, cephalosporin anti-infection treatment should be given in a timely manner. Secondly, it is caused by encephalitis in newborns. If a newborn has septic meningitis, this can cause an increase in intracranial pressure. The increased intracranial pressure will cause the newborn to spit up a lot of milk, and the pressure of spitting up will be very high, in the form of jets of milk. In this case, the newborn should be given timely anti-infection and intracranial pressure lowering treatment.