Background: Case-control studies have found increased head growth during the first year of life in children with autism spectrum disorder. Length and weight have not been as extensively studied, and there are few studies of population-based samples.
Methods: The study was conducted in a sample of 106,082 children from the population-based Norwegian Mother and Child Cohort. The children were born in 1999–2009; by the end of follow-up on 31 December 2012, the age range was 3.6 through 13.1 years (mean 7.4 years). Measures were obtained prospectively until age 12 months for head circumference and 36 months for length and weight. We compared growth trajectories in autism spectrum disorder cases and noncases using Reed first-order models.
Results: Subjects included 376 children (310 boys and 66 girls) with specialist-confirmed autism spectrum disorder. In boys with autism spectrum disorder, mean head growth was similar to that of other boys, but variability was greater, and 8.7% had macrocephaly (head circumference >97th cohort percentile) by 12 months of age. Autism spectrum disorder boys also had slightly increased body growth, with mean length 1.1 cm above and mean weight 300 g above the cohort mean for boys at age 12 months. Throughout the first year, the head circumference of girls with autism spectrum disorder was reduced—by 0.3 cm at birth and 0.5 cm at 12 months. Their mean length was similar to that of other girls, but their mean weight was 150–350 g below at all ages from birth to 3 years. The reductions in mean head circumference and weight in girls with autism spectrum disorder appear to be driven by those with intellectual disability, genetic disorders, and epilepsy.
Discussion: Growth trajectories in children with autism spectrum disorder diverge from those of other children and the differences are sex specific. Previous findings of increased mean head growth were not replicated.
From the aCentre for Paediatric Epidemiology and Biostatistics, UCL Institute of Child Health, London, United Kingdom; bThe Norwegian Institute of Public Health, Oslo, Norway; cThe Mailman School of Public Health, Columbia University, New York, NY; dNew York State Psychiatric Institute, New York, NY; eNational Institute of Neurological Disorders and Stroke, Bethesda, MD; fInstitute of Psychiatry, University of Oslo, Oslo, Norway; and gNic Waals Institute, Lovisenberg Hospital, Oslo, Norway.
L.L. and M.H. share joint senior authorship.
The Norwegian Mother and Child Cohort is supported by the Norwegian Ministry of Health and Care Services, the Norwegian Ministry of Education and Research, the Research Council of Norway/FUGE (grant 151918), the National Institute of Neurological Disorders and Stroke (NIH/NINDS), Bethesda (grant NS47537), and the National Institute of Environmental Health Sciences (NIH/NIEHS), Research Triangle Park, NC (contract NO-ES-75558). The Autism Birth Cohort study is funded by the NINDS (grant NS47537 [Lipkin]). P.S. is funded by the Research Council of Norway, grant numbers 185476 and 190694. L.L. is funded by a UK Medical Research Council (MRC) Career Development Award in Biostatistics. The Centre for Paediatric Epidemiology and Biostatistics is supported by the MRC in its capacity as the MRC Centre of Epidemiology for Child Health.
The authors report no conflict of interest.
Correspondence: Pål Surén, Norwegian Institute of Public Health, P.O. Box 4404 Nydalen, N-0403 Oslo, Norway. E-mail: firstname.lastname@example.org.
Received October 3, 2012
Accepted April 23, 2013