The large brains that give humans so many evolutionary advantages have created a head that is disproportionately large in comparison to the pelvis it must pass through during birth. Luckily this potential problem is solved by the amazing design of the infant skull. Our craniums (the domed part of our skulls above and behind our face) are actually made up of 5 bones that fuse together over time. At birth, these bones are still quite separate; joined only by a membrane along joints known as sutures. This is most commonly visible as the soft spot on a baby’s head which is called a fontanel.
During birth, as the baby’s head passes through the relatively narrow pelvis, these floating bones will move; stretching apart at the connective membrane, or sliding over and on top of one and other. This allows the head to pass through an opening that may not be a perfect fit.
So your baby’s head may be rather “unusually” shaped immediately after delivery, but it usually only takes about 24 hours for the bones to return to their natural location leaving your baby with a pleasingly perfect little noggin. As your baby grows, most the membranes between the cranial bones will ossify (turn into bone) by baby’s first birthday. The largest membrane covering the anterior fontanel – that familiar “soft spot” usually does not completely ossify until about age two.