title: The influence of head growth in fetal life, infancy, and childhood on intelligence at the ages of 4 and 8 years.
abstract: OBJECTIVE
  We investigated the effects of head growth prenatally, during infancy, and during later periods of development on cognitive function at the ages of 4 and 8 years.
  
  
  METHODS
  We studied 633 term-born children from the Avon Longitudinal Study of Parents and Children cohort whose head circumference was measured at birth and at regular intervals thereafter. Their cognitive function was assessed with the Wechsler Preschool and Primary Scale of Intelligence at the age of 4 years and with the Wechsler Intelligence Scale for Children at the age of 8 years. Linear regression analysis was used to calculate postnatal head growth between successive time points, conditional on previous size, and to examine the relationship between head growth during different periods of development and later IQ.
  
  
  RESULTS
  When the influence of head growth was distinguished for different periods, only prenatal growth and growth during infancy were associated with subsequent IQ. At 4 years, after adjustment for parental characteristics, full-scale IQ increased an average of 2.41 points for each 1-SD increase in head circumference at birth and 1.97 points for each 1-SD increase in head growth during infancy, conditional on head size at birth. At 8 years, head circumference at birth was no longer associated with IQ, but head growth during infancy remained a significant predictor, with full-scale IQ increasing an average of 1.56 points for each 1-SD increase in growth.
  
  
  CONCLUSIONS
  The brain volume a child achieves by the age of 1 year helps determine later intelligence. Growth in brain volume after infancy may not compensate for poorer earlier growth.
authors.affiliation: Medical Research Council Epidemiology Resource Centre, University of Southampton, Southampton General Hospital, Southampton SO16 6YD, United Kingdom. crg@mrc.soton.ac.uk
authors.forename: Catharine R
authors.initials: CR
authors.lastname: Gale
authors.forename: Finbar J
authors.initials: FJ
authors.lastname: O'Callaghan
authors.forename: Maria
authors.initials: M
authors.lastname: Bredow
authors.forename: Christopher N
authors.initials: CN
authors.lastname: Martyn
mesh_terms: D001921:Brain / Q000196:embryology* / Q000254:growth & development*; D002508:Cephalometry; D002648:Child; D002657:Child Development; D002675:Child, Preschool; D003071:Cognition; D005260:Female; D006801:Humans; D007223:Infant; D007231:Infant, Newborn; D007360:Intelligence; D007361:Intelligence Tests; D008137:Longitudinal Studies; D008297:Male