During routine checkups, the distance is measured in centimeters or inches and compared with:
- Past measurements of a child's head circumference
- Normal ranges for a child's sex and age (weeks, months), based on values that experts have obtained for normal growth rates of infants' and children's heads
Measurement of the head circumference is an important part of routine well-baby care. During the well-baby exam, a change from the expected normal head growth may alert the doctor of a possible problem.
For example, a head that is larger than normal or that is increasing in size faster than normal may be a sign of several problems, including water on the brain (hydrocephalus).
A very small head size (called microcephaly) or very slow growth rate may be a sign that the brain is not developing properly.