Head growth and neurocognitive outcomes.

BACKGROUND AND OBJECTIVES There is a lack of evidence on the value of head circumference (HC) as a screening measure. We aimed to describe the incidence of head centile shifting and the relationship between extremes of head size and later neurodevelopmental problems in the Avon Longitudinal Study of Parents and Children. METHODS HC was measured routinely at 2, 9, and 18 or 24 months and by researchers at ages 4, 8, 12, and 18 months. IQ according to the Wechsler Intelligence Scale for Children was measured in research clinics at age 8 for all. Neurocognitive disorders (NCDs) were identified from chart review. RESULTS There were 10 851 children with ≥2 head measurements. At each age, 2% to 3% of children had scores that were < -2 or >2 SDs below or above the mean, but for most children this was only found at 1 age. More than 15% of children showed centile shifts, but less than one-third of these were sustained at subsequent measurements. Only 0.5% showed a sustained shift beyond the normal range. Children with consistently small heads were up to 7 times more likely to have an NCD, but 85% of children with small heads had no NCDs, and 93% of children with NCDs had head SD scores within the normal range. CONCLUSIONS Centile shifts within the normal range occur commonly and seem mainly to reflect measurement error. This finding makes robust assessment of the head trajectory difficult and may result in many children being investigated unnecessarily. Extreme head size is neither specific nor sensitive for detecting NCDs, suggesting that routine measurement of HC is unhelpful.