Intrauterine growth and intelligence within sibling pairs: findings from the Mater-University study of pregnancy and its outcomes.
OBJECTIVE
To examine the association between intrauterine growth and intelligence.


METHODS
Population based birth cohort study of sibling pairs born within a maximum of three years of each other.


METHODS
Mater-University women and children's hospital, Brisbane, Australia.


METHODS
235 (470 children) sibling pairs.


RESULTS
Among one randomly selected sibling from each pair verbal comprehension at age 5, general intelligence at age 14, and reading ability at age 14 increased linearly with increasing gestational age and sex standardised birth weight z scores. With adjustment for maternal age, race, and smoking during pregnancy, birth order, family income, and parental education the associations with verbal comprehension at age 5 and general intelligence at age 14 remained, whereas the association with reading ability at age 14 was attenuated to the null. Within sibling pairs, differences in intrauterine growth were positively associated with differences in verbal comprehension at age 5 (test score difference per one unit difference in birth weight z score = 1.52 (0.11 to 3.26)) and general intelligence at age 14 (1.09 (0.01 to 2.18)), but not with reading ability at age 14.


CONCLUSIONS
Socioeconomic position or other fixed maternal characteristics do not seem to explain the positive association between intrauterine growth and childhood intelligence.
Lawlor
Debbie A
DA
Department of Social Medicine, University of Bristol, Canynge Hall, Whiteladies Road, Bristol BS8 2PR, UK. d.a.lawlor@bristol.ac.uk
Bor
William
W
O'Callaghan
Michael J
MJ
Williams
Gail M
GM
Najman
Jake M
JM
D000293:Adolescent; D001724:Birth Weight; D002675:Child, Preschool; D015331:Cohort Studies; D005260:Female; D047109:Fetal Development / Q000502:physiology*; D005865:Gestational Age; D006801:Humans; D007360:Intelligence / Q000502:physiology*; D007361:Intelligence Tests; D008297:Male; D009035:Mothers; D011247:Pregnancy; D011932:Reading; D012737:Sex Factors; D035781:Siblings; D012959:Socioeconomic Factors