Normal Head Circumference Growth in Newborns
The normal head circumference growth in newborns should be monitored using the WHO growth charts for children under 24 months, with measurements plotted on appropriate growth charts to track development over time. 1, 2
Measurement Technique
Head circumference measurement should be performed with precision:
- Use a firm, non-stretchable measuring tape
- Position the infant with head upright
- Locate the occipital bone at the back of the head and the supraorbital ridges
- Apply the tape firmly around the head just above the supraorbital ridges at the same level on both sides to the occiput
- Move the tape up or down slightly to obtain the maximum circumference
- Apply sufficient tension to press the hair against the skull
- Record the measurement to the nearest 0.1 cm 1, 2
Normal Growth Patterns
Expected Growth Rate
- Head circumference growth is not linear but occurs in saltatory patterns (intermittent growth spurts)
- Typical growth increments are approximately 0.20 cm in 24-hour periods
- These growth spurts are separated by intervals of no growth ranging from 1 to 21 days 3
- Head growth saltations are typically coupled to length growth saltations within a median timeframe of 2 days 3
Growth Chart Standards
- WHO growth charts are recommended for infants under 24 months
- CDC growth charts should be used for children aged 2-19 years 1
- When using WHO charts, the 2.3rd and 97.7th percentiles (±2 standard deviations) are recommended cutoffs for identifying abnormal growth 1
Ethnic Variations
- At 40 weeks gestation, infants of European descent typically have larger head circumferences than infants of Chinese descent (mean difference of 0.50 cm)
- South Asian and Chinese babies tend to have similar mean head circumferences at 40 weeks 4
- Consider using ethnicity-specific growth charts to prevent misclassification of newborns 4
Clinical Interpretation
Normal Range
- Normal head circumference falls between the 3rd and 97th percentiles (or ±2 standard deviations) for age and gender 2
- Microcephaly is defined as head circumference below -2 standard deviations or below the 3rd percentile 2
- Macrocephaly is defined as head circumference exceeding +2 standard deviations or above the 97th percentile 2
Growth Monitoring Considerations
- Serial measurements are more informative than single measurements
- Head circumference should be evaluated in relation to other growth parameters (weight and length)
- Abnormal head circumference may be the first sign of underlying neurological conditions 2
- For premature infants, measurements should be corrected for gestational age 5
- Infants with birth weight >1000g typically show head circumference growth similar to term infants
- Infants with birth weight ≤1000g often show slower head growth and may not "catch up" with larger premature or term infants 5
Maternal Factors
- Maternal height and weight influence newborn head circumference
- For term male newborns, head circumference can differ by up to 1.2 cm between babies born to mothers of short versus tall stature 6
- Consider maternal size when assessing newborn head circumference 6
Clinical Significance
- Regular monitoring of head circumference is crucial for:
- Detecting microcephaly or macrocephaly
- Assessing proportionality with other growth parameters
- Monitoring brain growth over time
- Identifying potential cases of neurological conditions 2
- Small head circumference (below 5th percentile) at second-trimester scan is associated with increased risk of neurological disorders, with worse outcomes when the head circumference is smaller 7
Remember that breastfed infants may show slower growth during ages 3-18 months compared to formula-fed infants, which is normal according to the WHO standards 1.