title: Changes in genetic and environmental effects on growth during infancy.
abstract: BACKGROUND
  Accelerated infant growth is a possible explanation for the relation between birth weight and adult diseases.
  
  
  OBJECTIVE
  The aim of this study was to estimate the heritability of infant growth and to examine whether the genetic contribution changes with increasing or decreasing birth weight and gestational age.
  
  
  METHODS
  Growth (change in weight z score) was analyzed in 522 infants from the East Flanders Prospective Twin Survey for age windows of 0-1, 1-6, 6-12, and 12-24 mo. Structural equation modeling was performed to estimate the relative importance of additive genetic, shared environmental, and unique environmental sources of variance.
  
  
  RESULTS
  We showed no genetic contribution to growth in the 0-1-mo growth period. However, at later ages, the heritability of growth was high at 94% (95% CI: 90%, 96%) from 1 to 6 mo, 85% (95% CI: 80%, 89%) from 6 to 12 mo, and 86% (95% CI: 77%, 91%) in the 12-24-mo growth period. Nevertheless, in the last age window, a model without genetic factors was also statistically plausible. From 0 to 1 mo, the genetic contribution to growth was low in the average birth weight range but higher at both extremes of birth weight. The genetic contribution from 0 to 1 mo increased with increasing gestational age from 36 wk of gestation onward.
  
  
  CONCLUSIONS
  This study shows that genetic factors are not important in early infant growth (0-1 mo), whereas heritability is high after 1 mo. Because many (nutritional) interventions are aimed at influencing early postnatal growth, to target long-term health, these interventions may be most successful if implemented in the first month of postnatal growth.
authors.affiliation: Department of Pediatrics, Nutrition and Toxicology Research Institute Maastricht, School for Nutrition, Toxicology and Metabolism, Netherlands. bob.touwslager@mumc.nl
authors.forename: Robbert N
authors.initials: RN
authors.lastname: Touwslager
authors.forename: Marij
authors.initials: M
authors.lastname: Gielen
authors.forename: Antonius L
authors.initials: AL
authors.lastname: Mulder
authors.forename: Willem J
authors.initials: WJ
authors.lastname: Gerver
authors.forename: Luc J
authors.initials: LJ
authors.lastname: Zimmermann
authors.forename: Tom
authors.initials: T
authors.lastname: Fowler
authors.forename: Alfons J
authors.initials: AJ
authors.lastname: Houben
authors.forename: Coen D
authors.initials: CD
authors.lastname: Stehouwer
authors.forename: Catherine
authors.initials: C
authors.lastname: Derom
authors.forename: Robert
authors.initials: R
authors.lastname: Vlietinck
authors.forename: Ruth J F
authors.initials: RJ
authors.lastname: Loos
authors.forename: Maurice P
authors.initials: MP
authors.lastname: Zeegers
mesh_terms: D000328:Adult; D001530:Belgium; D001724:Birth Weight; D001835:Body Weight / Q000235:genetics*; D004200:Diseases in Twins / Q000235:genetics*; D004777:Environment; D005260:Female; D020022:Genetic Predisposition to Disease; D005865:Gestational Age; D006128:Growth / Q000235:genetics*; D006801:Humans; D007223:Infant; D008297:Male; D009765:Obesity / Q000235:genetics*; D011446:Prospective Studies; D014427:Twins / Q000235:genetics; D055815:Young Adult