A baby's skull consists of five thin, curved bony plates that are held together by fibrous material called sutures . The skull is soft enough so that it can expand as a baby's brain grows. Usually, the area within a baby's skull doubles in the first 6 months of life and doubles again by age 2. Some sutures begin to close at about this time. After age 2, the skull and brain grow at a much slower rate.
The sutures gradually harden (ossify) to join the skull bones together. The spaces where sutures meet are called fontanelles or "soft spots."
If any of the sutures close too early, it may affect normal skull development, sometimes resulting in a misshapen head or other problems.
Babies born with certain conditions may have irregular fontanelles and sutures. For example, a baby born with congenital hydrocephalus may have wider sutures than normal, and the tissue covering the fontanelles may bulge.