Head Circumference Developmental Course in the First 14 Months of Life in Children with ASD

Background: Several retrospective, prospective and postmortem studies have reported increased incidences of macrocephaly (head circumference > 97^th centile). On the basis of this findings, it has been suggested that macrocephaly could represent a clinical marker for grouping individuals with autism.

Objectives: The present study aims to describe head circumference developmental course in the first 14 months of life in a large group of children with ASD.

Methods: 50 patients with ASD were recruited at Centre for Autism at the Stella Maris Scientific Institute in Pisa. All patients were full term at birth and parents were in possession of the pediatric records reporting head circumference (HC), height (H) and weight (W) measurements at four age periods: birth (T0); 1-to-2 months (T1); 3-to-5 months (T2) and 6-to-14 months (T3). HC, height and weight data from 100 healthy children, from healthy pediatric population followed by several italian pediatrician in the metropolitan area of Pisa were made available to us for comparison with the ASD sample.
t-Test and analysis of variance for repeated measures, with Bonferroni post-hoc test, was performed to compare differences in HC, weight and height at the considered periods between ASD and healthy infants.
Results: At T2 and at T3 HC was significantly greater in ASD group compared to healthy infants.
At T1, T2 and T3 weight was significantly smaller in ASD group compared to healthy infants.
With respect to height there are no significant differences between AS D group compared to healthy infants in all four considered periods (T0,T1,T2 and T3).
Analysis of variance for repeated measures showed that, over time, the rate of HC was growth in both groups, but the growth was greater in ASD subjects compared with healthy infants.
ASD group showed a smaller weight than control group at all time points, but no differences were found in the rate of weight growth between the two groups. With respect to rate of height growth, there were no significant differences between the two groups. In order to assess the differences between the rate of HC between the two groups, regardless of body size, we performed a new analysis of variance for repeated measures, controlling for weight and height. After controlling for both height and weight, the rate of HC growth was different between groups, in particular, change in HC growth continued to be significantly greater in the ASD group compared with the control group.

Conclusions: This study confirmed the existence of an abnormal rate of growth of HC in the first two years of life in children affected by PDD, characterised by a sudden and excessive increase in head size between 3-5 and 6-14 months. Moreover, it confirmed the association between ASD and macrocephaly at 6-14 months of life. Finally, it outlines the importance to measure the HC in the first months of life of children because an its abnormal rate of growth, in association with other clinical signs, may serve as an early warning signal of risk for autism.