Children's Health

The skull consists of five thin, curved, bony plates that are held together by fibrous material called sutures. These sutures allow a baby's skull to expand with the growing brain. 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 ossify (gradually harden) to join the skull bones together. The spaces where sutures meet are called fontanelles. At birth, they are covered with a membrane (a thin layer of tissue), which are often called "soft spots." See an illustration of the sutures and fontanelles .

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.