when does baby's skull harden
The ossification of the bones of the skull causes the anterior fontanelle to close over by 9 to 18 months. The sphenoidal and posterior fontanelles close during the first few months of life. The closures eventually form the sutures of the neurocranium.
The anterior fontanelle is more obvious and can be easily felt as a slightly soft area of skin on the top of the head. This does not close until well after your baby's first birthday, usually after 18 months. Keep an eye on your baby's fontanelles. They can give important clues to the state of her health.