A baby's brain and head do 80 percent of their growing during the first two years. Measuring head circumference helps doctors track the brain's growth as the skull bones fuse together. It's normal for a baby's head size to seem disproportionate to her height and weight. The usual explanation is genetics: If a baby's parents have big heads, the baby will probably have one too. Remember that the size of your child's head relative to the rest of her body (especially at such a young age) is less important than a consistent pattern of growth (not too fast or too slow).
Copyright© 2004. Reprinted with permission from the June 2001 issue of Parents magazine. Updated 2009