title: Gestational age and cognitive ability in early childhood: a population-based cohort study.
abstract: BACKGROUND
  Recent studies suggest that children born at late preterm (34-36 weeks gestation) and early term (37-38 weeks) may have poorer developmental outcomes than children born at full term (39-41 weeks). We examined how gestational age is related to cognitive ability in early childhood using the U.K. Millennium Cohort Study.
  
  
  METHODS
  Cognitive development was assessed using Bracken School Readiness Assessment at age 3 years, British Ability Scales II at ages 3, 5 and 7 years and Progress in Mathematics at age 7 years. Sample size varied according to outcome between 12,163 and 14,027. Each gestational age group was compared with the full-term group using differences in z-scores and risk ratios for scoring more than -1 SD below the mean.
  
  
  RESULTS
  Children born at <32 weeks gestation scored lower (P < 0.05) than the full-term group on all scales with unadjusted z-score differences ranging between -0.8 to -0.2 SD. In all groups, there was an increased risk (P < 0.05) of scoring less than -1 SD below the mean compared with the full-term group for some of the tests: those born at < 32 weeks had a 40-140% increased risk in seven tests, those born at 32-33 weeks had a 60-80% increased risk in three tests, those born at 34-36 weeks had a 30-40% increased risk in three tests, and those born at 37-38 weeks had a 20% increased risk in two tests.
  
  
  CONCLUSIONS
  Cognitive ability is related to the entire range of gestational age, including children born at 34-36 and 37-38 weeks gestation.
authors.affiliation: National Perinatal Epidemiology Unit, University of Oxford, Oxford.
authors.forename: Gry
authors.initials: G
authors.lastname: Poulsen
authors.forename: Dieter
authors.initials: D
authors.lastname: Wolke
authors.forename: Jennifer J
authors.initials: JJ
authors.lastname: Kurinczuk
authors.forename: Elaine M
authors.initials: EM
authors.lastname: Boyle
authors.forename: David
authors.initials: D
authors.lastname: Field
authors.forename: Zarko
authors.initials: Z
authors.lastname: Alfirevic
authors.forename: Maria A
authors.initials: MA
authors.lastname: Quigley
mesh_terms: D002648:Child; D002657:Child Development / Q000502:physiology*; D002675:Child, Preschool; D003071:Cognition / Q000502:physiology*; D015331:Cohort Studies; D002658:Developmental Disabilities / Q000523:psychology*; D005865:Gestational Age; D006801:Humans; D007231:Infant, Newborn; D007234:Infant, Premature; D016017:Odds Ratio; D011581:Psychological Tests; D006113:United Kingdom