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.