Have you ever noticed that a baby’s head tends to look larger than his or her body? Baby head circumference starts out rather large in order to give the baby’s brain enough room for the rapid growth that will happen through the age of two. In fact, the brain and head attain 80 percent of expected growth during the first two years. But baby head circumference is just one part of the picture. It matters, but so do other things like developmental milestones and physical health.

How to Measure Baby Head Circumference

The circumference of a baby’s head is measured with a simple measuring tape. The tape goes around the largest part of the baby’s head, just above the ears. Though it is an absolutely painless test that yields important information, most babies don’t like it and might throw a fit, especially when they are a bit older and get anxious about going to the doctor or the touches of strangers.

What Does Baby Head Circumference Mean?

The measurement of circumference is then plotted on a growth chart. This growth chart will explain just where in the spectrum of size your baby falls. The percentile range typically goes up to 100. For instance, if your baby’s head is in the 20th percentile, that means that out of 100 babies, 20 of them have a smaller circumference.

Sometimes a lower number is simply hereditary – if a child has smaller parents, it makes sense that he or she will be smaller in size all over, including the head. But if all seems well while your baby has a tinier head circumference than most, it might mean a problem with brain development. On the other hand, a large head circumference might not be good either, because that could mean there is fluid on the brain or it is otherwise growing too rapidly.

However, keep in mind that this is not the only indication of health. A baby head circumference must always be taken along with other points of health in order to decide if it is a serious issue or not.

What Is Normal Baby Head Circumference?

An average newborn will have a head circumference of about 13 ¾ inches (34.9 cm) at birth, assuming the baby was full-term. By one month, that has grown to 15 inches (38.1 cm). Baby head circumference in boys might be slightly larger than in girls, but it is still rather close, within one centimeter or so.

Baby head circumference varies and all might be normal. However, the rule of thumb is that during the first six months, the baby’s head will be about two centimeters bigger than his or her chest. From six months to two years, the baby’s head will be about the same size as the chest. After the age of two, the baby’s body outpaces head growth.

Baby Head Circumference and Intelligence

Does a bigger baby head circumference indicate that your little one is smarter than others? That question was addressed in a study of over 600 British babies. Here are the results:

1. Head Growth by Age One Matters

Researchers took the measurements of baby heads at birth, one year, four years and eight years. They then administered an IQ test to children at the ages of four and eight. Those children who had larger heads at the age of one tended to have higher IQ scores than children who had smaller heads. This might indicate that brain growth before the age of one has a big impact on how smart a child will be.

2. Parents Also Play a Role

It is important to note that other factors came into play as well. The parents were interviewed, and researchers found that those who held higher education, who had breastfed their child for at least three or four months and had higher scores on the parenting questionnaire tended to have children who tested in the highest IQ levels. Therefore, keep in mind that though baby head circumference matters, so does the environment in which the child grows up.