What Your Infant's Head Size Means

Julie Kirk
Reviewed by Terri Forehand RN
doctor measuring infant head

Pediatricians use growth charts to monitor various newborn measurements, including infant head size. How big an infant's head size is, may provide crucial information about your baby.

Unusual Infant Head Size May Indicate a Health Issue

An infant head size measurement can give physicians an idea about a baby's brain development. An average, full-term newborn will have a head circumference of about 34 to 35 centimeters (13 3/4 inches). This puts the newborn at the 50th percentile for their head circumference measurement. When a baby's head size is considerably bigger or smaller than average, it may indicate a problem or health issue.

Newborn With a Large Head

While a newborn may have a large head size due to heredity, it could also mean that there is a problem in the brain that may require surgery. One reason your newborn may have a larger than normal head size is due to hydrocephalus which is excess fluid in the brain. If your newborn has a larger than normal head size, he or she may be diagnosed with macrocephaly ('big head'). This is when the head circumference measures greater than 38 centimeters and puts your baby over the 97th percentile for their head measurement.

Baby With an Unusually Small Head

If a baby has a smaller than normal head size, it may be related to their parent's head size, preterm birth or it may be an indication of a lack of normal brain development. Your baby may have microcephaly, which is a condition where the newborn's head is considerably smaller than an average newborn. This is when the head circumference measures less than 31 centimeters and would put your baby under the 3rd percentile for their head measurement.

Correlation Between Head Size and Autism Risk

Earlier studies have claimed that there was a possible correlation between a larger head size and the risk of autism. Now there appears to be conflicting information on this matter. One recent study shows that there is no evidence of early head circumference enlargements in children later diagnosed with autism. Another recent study shows mixed findings of a link between fetal head growth, autistic traits, and autism spectrum disorder and suggests further research is needed in this area.

Head Size and Intelligence

If your baby has a bigger head size, he or she will probably have a bigger brain. However, a bigger brain doesn't necessarily mean a smarter baby. It is important that your baby receives various types of repetitive and consistent stimulation in order to learn. This is what will ultimately help develop their intelligence. Another indicator of intelligence is when your baby reaches his or her developmental milestones in a timely manner.

Growth Charts and Percentiles

The website Infant Head Circumference Chart offers an online growth chart calculator that shows how your baby's head circumference compares to other babies. For example, if your baby's head size receives a percentile value of 60, this indicates that your baby's head circumference is greater than 60 out of 100 babies.

Physicians often refer to these growth percentiles as they plot a child's development. This data is typically shown as a curved pattern of lines on a chart. The higher or lower the percentile that is plotted, the bigger or smaller the measurement is respectively for a child compared with other children who are the same age and gender.

Monitoring Your Baby

As your baby grows, it is important to keep track of these measurements to monitor growth. You should also pay attention to the various developmental milestones that your baby needs to achieve within a certain timeframe. As always, if you have any worries or concerns, contact your pediatrician immediately.

What Your Infant's Head Size Means