# How do you measure the circumference of a baby’s head?

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Head circumference is generally measured on infants and children until age three years. Head circumference or OFC [occipital frontal circumference] is measured over the most prominent part on the back of the head (occiput) and just above the eyebrows (supraorbital ridges).

## What is a normal baby head circumference?

The average newborn’s head circumference measures about 13 3⁄4 inches (35 cm), growing to about 15 inches (38 cm) by one month. Because boys tend to be slightly larger than girls, their heads are larger, though the average difference is less than 1⁄2 inch (1 cm).

## At what age is head circumference measured?

Head circumference is measured in children up to age 3, as this is the time of greatest brain growth. It is correctly measured using a flexible tape measure at the maximum diameter through the supraorbital ridge to the occiput.

## Why do we measure baby’s head circumference?

Head circumference is measured because it’s an easy way to tell if there’s a potential problem or if something needs to be watched. For example, if the head grows too fast, it could sign hydrocephalus or water on the brain. If the head grows too slowly, it could be a sign of microcephaly or a smaller head than normal.

The simple definition of the word macrocephaly is “large head.” Doctors apply that diagnosis when a baby’s head size is in the 98th percentile. This means that the baby’s head is bigger than 98% percent of other babies of the same age. Sometimes, doctors detect macrocephaly during an ultrasound before the baby is born.

## Is 32 cm head circumference at birth?

Normal head circumferences in term infants range from 32 to 38 cm. Microcephaly is defined as a head circumference 2 standard deviations (SDs) below the mean for age and sex or roughly less than the 2nd percentile.

## Is 36 cm head circumference at birth?

The average newborn’s head measures 13 3/4 in (35 cm) Generally, a newborn’s head is about half the baby’s body length in cm plus 10 cm. So a baby that is 18 inches long would be 45.7 centimeters (18 x 2.54). His or her head would be about 32.9 cm or a little under 13 inches.

## How long should head circumference be measured?

The cranium is documented to grow from birth through adolescence. The standard of practice in primary care is measuring head circumference and plotting growth using curves that stop at 36 months.

## How do you measure head circumference on ultrasound?

Measurement technique

If the available ultrasound equipment allows for measurement of an ellipse, this may be drawn around the outside of the calvarium. Alternatively, HC may be calculated from BPD and occipitofrontal diameter (OFD) as: HC = 1.62 × (BPD + OFD) 3.

## How do I know if my baby has microcephaly?

To diagnose microcephaly after birth, your baby’s provider measures your baby’s head circumference during a physical exam. Head circumference is the distance around your baby’s head. Your baby’s provider then compares your baby’s measurement to that of other babies of the same sex and age.

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## Does head circumference correlate with IQ?

At 8 years, head circumference at birth was no longer associated with IQ, but head growth during infancy remained a significant predictor, with full-scale IQ increasing an average of 1.56 points for each 1-SD increase in growth.

## What happens if a baby’s head circumference is small?

Chances are your doctor will detect microcephaly at the baby’s birth or at a regular well-baby checkup. However, if you think your baby’s head is smaller than normal or isn’t growing as it should, talk to your doctor.

## What is abnormal head circumference?

Macrocephaly refers to an overly large head. It’s often a symptom of complications or conditions in the brain. There’s a standard used to define macrocephaly: The circumference of a person’s head is more than two standard deviations above average for their age. Or, their head is larger than the 98th percentile.

## Do autistic babies have large heads?

After accounting for sex, height, weight and genetic ancestry, the researchers found that children with autism do tend to have larger heads than their unaffected siblings, but the difference is small: just 2 millimeters on average.

## What is the normal percentile for head circumference?

A percentile of 50% represents the average or mean head circumference. A value below 50 percent means a baby’s head circumference is less than the average. A value greater than 50 percent means a baby’s head circumference is above average.