The amount of milk your baby sucks depends on his stomach content and digestive condition. The volume of stomach contents is about 30 to 60 ml for newborns, 90 to 150 ml for 1 to 3 months old, and 250 to 30 ml for one year olds. The stomach of newborns is horizontal, with less secretion of hydrochloric acid and various enzymes than that of adults, and with low enzyme activity and poor digestive function. Due to the low tension of the cardia and gastric fundus and the well-developed pyloric sphincter, vomiting is likely to occur due to pyloric spasm.