title: Early head growth in infants at risk of autism: a baby siblings research consortium study.
abstract: OBJECTIVE
  Although early brain overgrowth is frequently reported in autism spectrum disorder (ASD), the relationship between ASD and head circumference (HC) is less clear, with inconsistent findings from longitudinal studies that include community controls. Our aim was to examine whether head growth in the first 3 years differed between children with ASD from a high-risk (HR) sample of infant siblings of children with ASD (by definition, multiplex), HR siblings not diagnosed with ASD, and low-risk (LR) controls.
  
  
  METHODS
  Participants included 442 HR and 253 LR infants from 12 sites of the international Baby Siblings Research Consortium. Longitudinal HC data were obtained prospectively, supplemented by growth records. Random effects nonlinear growth models were used to compare HC in HR infants and LR infants. Additional comparisons were conducted with the HR group stratified by diagnostic status at age 3: ASD (n = 77), developmental delay (DD; n = 32), and typical development (TD; n = 333). Nonlinear growth models were also developed for height to assess general overgrowth associated with ASD.
  
  
  RESULTS
  There was no overall difference in head circumference growth over the first 3 years between HR and LR infants, although secondary analyses suggested possible increased total growth in HR infants, reflected by the model asymptote. Analyses stratifying the HR group by 3-year outcomes did not detect differences in head growth or height between HR infants who developed ASD and those who did not, nor between infants with ASD and LR controls.
  
  
  CONCLUSIONS
  Head growth was uninformative as an ASD risk marker within this HR cohort.
authors.affiliation: University of Alberta, Edmonton, Alberta, Canada. Electronic address: lonniez@ualberta.ca.
authors.forename: Lonnie
authors.initials: L
authors.lastname: Zwaigenbaum
authors.affiliation: University of California, Davis.
authors.forename: Gregory S
authors.initials: GS
authors.lastname: Young
authors.affiliation: University of Washington, Seattle.
authors.forename: Wendy L
authors.initials: WL
authors.lastname: Stone
authors.affiliation: University of California, San Diego.
authors.forename: Karen
authors.initials: K
authors.lastname: Dobkins
authors.affiliation: University of California, Davis.
authors.forename: Sally
authors.initials: S
authors.lastname: Ozonoff
authors.affiliation: University of Toronto, Ontario, Canada.
authors.forename: Jessica
authors.initials: J
authors.lastname: Brian
authors.affiliation: Dalhousie University, Halifax, Nova Scotia, Canada.
authors.forename: Susan E
authors.initials: SE
authors.lastname: Bryson
authors.affiliation: University of California, San Diego.
authors.forename: Leslie J
authors.initials: LJ
authors.lastname: Carver
authors.affiliation: University of California, Los Angeles.
authors.forename: Ted
authors.initials: T
authors.lastname: Hutman
authors.affiliation: University of Pittsburgh.
authors.forename: Jana M
authors.initials: JM
authors.lastname: Iverson
authors.affiliation: Kennedy Krieger Institute and Johns Hopkins School of Medicine, Baltimore.
authors.forename: Rebecca J
authors.initials: RJ
authors.lastname: Landa
authors.affiliation: University of Miami.
authors.forename: Daniel
authors.initials: D
authors.lastname: Messinger
mesh_terms: D000067877:Autism Spectrum Disorder / Q000175:diagnosis*; D015415:Biomarkers; D002675:Child, Preschool; D005260:Female; D006257:Head / Q000254:growth & development*; D006801:Humans; D007223:Infant; D008137:Longitudinal Studies; D008297:Male; D012306:Risk; D035781:Siblings
chemical_list: D015415:Biomarkers
keywords: autism spectrum disorder; early detection; head circumference; high-risk design; longitudinal study