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What Does My Baby’s Head Circumference Mean?

Many NetWellness visitors have had questions about the significance of their newborn baby’s head circumference. But what exactly does this measurement mean?


When your baby’s head is measured during normal check-ups, health care professionals are monitoring one part of your baby’s growth. This measurement is then plotted on standardized growth charts and can give a general idea about your baby’s overall growth. For example, a head circumference at the 10th percentile means that out of 100 infant girls, there are only 10 girls with head circumferences smaller than the baby.

Do Measurements Matter?

A small head circumference can mean several things. You as parents may tend to have smaller than average (the 50th percentile) head sizes, so that the baby’s head measurements simply reflect his or her genetic heritage. However, it may also mean that the baby’s brain is not growing well during this crucial period of the brain growth spurt that lasts until 2 years of age. This is called microcephaly, or a failure of brain development. If the baby is preterm, it would be the ideal that the head circumference moderately exceeds the growth percentiles for weight and length, indicating that her brain was experiencing “catch up growth” after the challenges his or her early life in the hospital.

A large head circumference can also indicate some things. As with smaller head sizes, genetics can also play a role in larger head sizes. In the worst case, a large head size may signal hydrocephalus, or an excessive amount of fluid in the brain’s ventricles. This results in compression of the normal brain tissue and impairs the brain’s neurological function and growth.

Regarding International Adoptions

There is no way at this very early period of life to predict well what the developmental outcomes will be for your adopted child. If he or she was born prematurely, the mother received little or no prenatal care, if the baby was exposed to drugs or alcohol, the baby was exposed to HIV/AIDS, or suffered from asphyxia at birth or infections as a baby, there is a greater likelihood that a smaller or larger head circumference measurement means that the baby is at greater risk for mental retardation or other developmental delays. It would be helpful to request a more thorough history of the mother’s health and prenatal course and the baby’s birth, including Apgar scores. Apgar scores provide a picture of how vigorous and well the baby was at the time of her delivery. The higher the score, with 10 being perfect, the better. Reviewing this information with a pediatrician might provide you with a better idea of the risk for developmental disability.

Consult Your Health Care Professional

Overall, the head circumference cannot be the only measurement taken into consideration when determining a baby’s developmental progress. Parents should also look to make sure the baby is reaching his or her developmental milestones, since this is the key indicator of brain/neurologic growth and health. Head circumference is less worrisome if appropriate developmental milestones are occurring on time. If you or your health care provider have any questions regarding your child’s development, a developmental evaluation may be requested from an experienced pediatric physical/occupational therapist.

For more information:

Go to the Children’s Health health topic.