The baby will act disinterested in the milk. The child may act uncomfortable after feeding such as crying and drawing his legs up to his stomach. He may also vomit after eating. Unlike usual spit up this would be more violent.
Newborn babies are excellent at regulating their feeding needs.Wether you are feeding them formula or breastmilk,your baby will let you know when they want to be fed and when they have had enough.If you feel that your baby is overeating, you should contact your pediatrician.