Baby head measurement is tricky
Baby head measurement is one of 3 key measurements when it comes to monitoring baby and child growth. The distance around a person’s head is known as their head circumference. Head circumference in infancy is particular important because it is related to the growth of the brain.
It’s not easy to measure head circumference. Imagine measuring the distance around a volleyball with a tape or string. You’ll get it right if you can do so at the equator of the ball. If your string slides up or down, your reading will be too low.
A person’s head is more difficult to measure than a ball because a head is lumpy and far from spherical. Exactly where should you put the tape or string? Measuring a baby can be even harder because they are apt to move and push the string away. Never fear, here’s how to do it.
- Non-stretchable lace or piece of string that is at least 1 m (1 yard) long;
- measuring tape, yard stick, or a meter stick;
- paper and pencil;
- helper (this is a 2-person job);
- and, most crucially, a baby.
First, make sure that your baby has no items on his or her head that may interfere with the measurements, such as braids, barrettes, or ribbons.
Review the following video and record the length measurement in centimetres or inches on the paper. If possible, record fractional parts of your unit of measurement.
Have your partner take their own reading — without knowing yours. Compare the two readings. It is likely that they differ. If so, calculate the average of the two (an average is more reliable than either single reading).
Compare your baby’s head size to world norms
Now that you have your baby’s length, compare it to norms developed by the World Health Organization (WHO).
The WHO collected size measurements from 8,440 children in 6 countries from various regions of the world. These children were were not raised in environments with poor diets. They were healthy and their mothers followed health practices such as breastfeeding and not smoking during and after pregnancy.
If you have measured your baby in inches, you’ll first need to convert from inches to centimetres to inches use the chart. Just multiply your inches’ result by 2.54 to get your baby’s size in centimetres.
Healthy babies can differ greatly in head size, and head circumference percentiles are a numerical way of describing them. Do not treat the percentile result like a school grade. A higher percentile is not better than a lower percentile.
Many factors can influence your baby’s head size. For example, a baby born prematurely will have a smaller head size at 1 month of age than will a baby who was born a week after the due date.
However, an extremely small (<3%) or large (>97%) percentile may be a sign of developmental difficulty. If this is the case for your baby, you should consult a health care professional.