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Etiology of individual differences in birth weight of twins as a function of maternal smoking during pregnancy

Published online by Cambridge University Press:  21 February 2012

Caroline GM van Baal*
Affiliation:
Vrije Universiteit, Amsterdam, The Netherlands. gcm.van.baal@psy.vu.nl
Dorret I Boomsma
Affiliation:
Vrije Universiteit, Amsterdam, The Netherlands.
*
*Correspondence: Dr GCM van Baal, Dept of Biological Psychology, De Boelelaan 1111, 1081 HV Amsterdam, The Netherlands. Tel: (31) (20) 444 8802; Fax: (31) (20) 444 8832

Abstract

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Birth weight is in large extent influenced by gestational age. In addition genetic and environmental factors determine intrauterine growth and birth weight. The contributions of these factors may be influenced by maternal smoking during pregnancy. We examined birth weight and maternal smoking in a sample of 2930 twin pairs from the Netherlands Twin Register using structural equation modelling. Gestational age accounted for 27–44% of the variance in birth weight. A lower variability of birth weight and a lower association of birth weight with gestational age was found in twins whose mothers smoked during pregnancy. The variance not associated with gestational age was independent of maternal smoking during pregnancy. A systematic smaller part of the variability in birth weight was associated with variability in gestational age in second born twins compared to first born twins. The heritability of interindividual differences in birth weight was modest (10% for twins with non-smoking mothers and 11% for twins with smoking mothers). Common environmental influences other than gestational age accounted for a slightly larger part of the variance not associated with gestational age (17–20%).

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Articles
Copyright
Copyright © Cambridge University Press 1998