Although babies are ready to live and grow outside the womb, parts of their bodies are still immature. Your new baby’s body is all brand new and never been used before. It will take the first 3 months to get your baby’s digestive system running smoothly. You can tell by your baby’s face when they’re focused on whatever’s going on inside their tummy.
Your new baby will move their body while they’re awake, but your baby doesn’t know how to make each part of their body move, or even that all the bits belong to them. In the first 8 weeks, your baby has no control over their movements; the movements are an involuntary reflex. Sucking, grasping (holding something tight in the hand), and startling (‘jumping’ when there is a loud noise or when they're suddenly moved) are all reflexes. From about 8 weeks, your baby will begin to watch their hands and feet wave in the air, and to wave their fist towards your face or something they want. Your baby’s starting to get the idea that they have a body that moves, feels and has skin all around it, and that they have some control over what it does. Your baby will start to work out how to lift their head when lying on their tummy, and kick their legs.
Even though your baby can’t roll, they can wriggle and kick, so never leave them alone on a high surface such as your bed or a change table.