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Head Circumference Growth Charts
Data collected in the WHO Multicentre Growth Reference Study has been standardized to provide growth charts for boys and girls, from birth to 5 years of age, for normal head circumference.
The child’s measurement and age are plotted on the growth chart or retrieved in the percentile table, and may be interpreted as follows:
| Head circumference status | Growth chart percentile |
| Microcephaly | below 2nd percentile |
| Normal head circumference | between 2nd and 98th percentile |
| Macrocephaly | above the 98th percentile |
Pediatricians and other health professionals may use head circumference measurements to determine whether the baby’s brain is growing and developing normally. This measurement is routinely performed in babies under the age of 2. Where a larger measurement is found, a CT scan may be ordered to check for hydrocephalus.
To measure the head circumference, a flexible tape measure is extended from the middle of the forehead to the farthest part in the rear of the head.
In the case of normal development, two subsequent measurements at different ages should usually follow the same percentile.