The influence of birth size on intelligence in healthy children.
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.
Broekman
Birit F P
BF
Department of Psychological Medicine, National University of Singapore/National University Health System, Singapore 119074, Singapore.
Chan
Yiong-Huak
YH
Chong
Yap-Seng
YS
Quek
Swee-Chye
SC
Fung
Daniel
D
Low
Yen-Ling
YL
Ooi
Yoon-Phaik
YP
Gluckman
Peter D
PD
Meaney
Michael J
MJ
Wong
Tien-Yin
TY
Saw
Seang-Mei
SM
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