title: Birth weight and subsequent body mass index in children: an international cross-sectional study.
abstract: The reported association between birth weight and subsequent body mass index (BMI) is conflicting.
  
  
  
  To examine the relationship between birth weight and BMI in children aged 6-7 years.
  
  
  
  Secondary analysis of data from a multi-centre, multi-country, cross-sectional study (International Study of Asthma and Allergies in Childhood (ISAAC) Phase Three). Parents/guardians of children aged 6-7 years completed questionnaires about their children's birth weight, current height and weight and whether their mother smoked in the first year of the child's life. A general linear mixed model was used to determine the association between BMI and birth weight.
  
  
  
  A total of 72 111 children (17 countries) were included in the analysis. There was a positive association of birth weight with BMI (for each kg increase in birth weight the BMI at 6-7 increased by 0.47 (SE 0.02) kg/m2; p < 0.0001) with a clear gradient by birth weight category. There was no statistically significant interaction between birth weight and Gross National Income (GNI).
  
  
  
  There is a positive linear relationship between birth weight and BMI in 6-7 year old children, which is present in both high and low income countries.
authors.affiliation: Department of Paediatrics, Child and Youth Health, Faculty of Medicine and Health Sciences, The University of Auckland, Auckland, New Zealand.
authors.forename: E A
authors.initials: EA
authors.lastname: Mitchell
authors.affiliation: School of Population Health, The University of Auckland, Auckland, New Zealand.
authors.forename: A W
authors.initials: AW
authors.lastname: Stewart
authors.affiliation: Medical Research Institute of New Zealand, Wellington, New Zealand.
authors.forename: I
authors.initials: I
authors.lastname: Braithwaite
authors.affiliation: Department of Preventive and Social Medicine, Dunedin School of Medicine, University of Otago, Dunedin, New Zealand.
authors.forename: R J
authors.initials: RJ
authors.lastname: Hancox
authors.affiliation: Department of Medicine, Faculty of Medicine and Health Sciences, The University of Auckland, New Zealand.
authors.forename: R
authors.initials: R
authors.lastname: Murphy
authors.affiliation: Department of Nutrition, The University of Auckland, New Zealand.
authors.forename: C
authors.initials: C
authors.lastname: Wall
authors.affiliation: Medical Research Institute of New Zealand, Wellington, New Zealand.
authors.forename: R
authors.initials: R
authors.lastname: Beasley
mesh_terms: D001249:Asthma; D001724:Birth Weight; D015992:Body Mass Index; D002648:Child; D002675:Child, Preschool; D003430:Cross-Sectional Studies; D005260:Female; D006801:Humans; D008297:Male; D009035:Mothers; D011795:Surveys and Questionnaires
keywords: Birth weight; body mass index; child; epidemiology; gross national income