title: The influence of birth size on intelligence in healthy children.
abstract: OBJECTIVE
  Birth parameters have been hypothesized to have an influence on IQ. However, studies within the range of normal birth size have been sparse. With this study we examined the associations between birth length, birth weight, head circumference, and gestational age within the normal birth size range in relation to childhood IQ in Asian children.
  
  
  METHODS
  A cohort of 1979 of 2913 Asian children aged 7 to 9 years, recruited from 3 schools in Singapore, were followed yearly from 1999 onward. Birth parameters were recorded by health personnel. Childhood IQ was measured with the Raven's Standard Progressive Matrices at ages 8 to 12.
  
  
  RESULTS
  The mean IQ score across the sample (n = 1645) was 114.2. After controlling for multiple confounders for every 1-cm increment in birth length, 1 kg in birth weight, or 1 cm in head circumference, there was a corresponding increase in IQ of 0.49 points (P for trend < .001), 2.19 points (P for trend = .007) and .62 points (P for trend = .003), respectively. These associations persisted even after exclusion of premature children and children with extreme weights and head circumferences.
  
  
  CONCLUSIONS
  Longer birth length, higher birth weight, or larger head circumferences within the normal birth size range are associated with higher IQ scores in Asian children. Our results suggest that antenatal factors reflected in altered rates of growth but within the normative range of pregnancy experiences play a role in generating cognitive potential. This has implications for targeting early intervention and preventative programs.
authors.affiliation: Department of Psychological Medicine, National University of Singapore/National University Health System, Singapore 119074, Singapore.
authors.forename: Birit F P
authors.initials: BF
authors.lastname: Broekman
authors.forename: Yiong-Huak
authors.initials: YH
authors.lastname: Chan
authors.forename: Yap-Seng
authors.initials: YS
authors.lastname: Chong
authors.forename: Swee-Chye
authors.initials: SC
authors.lastname: Quek
authors.forename: Daniel
authors.initials: D
authors.lastname: Fung
authors.forename: Yen-Ling
authors.initials: YL
authors.lastname: Low
authors.forename: Yoon-Phaik
authors.initials: YP
authors.lastname: Ooi
authors.forename: Peter D
authors.initials: PD
authors.lastname: Gluckman
authors.forename: Michael J
authors.initials: MJ
authors.lastname: Meaney
authors.forename: Tien-Yin
authors.initials: TY
authors.lastname: Wong
authors.forename: Seang-Mei
authors.initials: SM
authors.lastname: Saw
mesh_terms: D001724:Birth Weight; D001827:Body Height; D002508:Cephalometry / Q000706:statistics & numerical data*; D002648:Child; D015331:Cohort Studies; D005260:Female; D005865:Gestational Age; D006306:Health Surveys; D006801:Humans; D007231:Infant, Newborn; D007234:Infant, Premature / Q000523:psychology*; D007360:Intelligence; D008297:Male; D012016:Reference Values; D012846:Singapore; D013223:Statistics as Topic