Head circumference measurement

What it is

Head circumference measurement is the routine measuring of the distance around the largest part of a baby's head, using a tape measure. It is one of the most valuable and simplest tools for monitoring for hydrocephalus in infants.

Understanding Head circumference measurement

Because an infant's skull can expand, hydrocephalus often shows up first as accelerating head growth. Measuring head circumference at routine well-child and follow-up visits, and plotting it on standardized growth charts, allows the team to detect a head that is growing too fast — crossing upward across percentiles — which prompts evaluation. A single measurement matters less than the trend over time. This simple, inexpensive, noninvasive measurement is a cornerstone of monitoring babies with or at risk for hydrocephalus, and families are sometimes taught to measure at home as part of follow-up.

Why it matters

Understanding head circumference measurement helps families see why this simple measurement is taken and tracked at every infant visit, and why the trend over time — not a single number — is what signals possible hydrocephalus.