title: Age at Weaning and Infant Growth: Primary Analysis and Systematic Review.
abstract: OBJECTIVE
  To test whether earlier age at weaning (age 3-6 months) may promote faster growth during infancy.
  
  
  METHODS
  Weaning at age 3.0-7.0 months was reported by 571 mothers of term singletons in a prospective birth cohort study conducted in Cambridge, UK. Infant weight and length were measured at birth and at age 3 months and 12 months. Anthropometric values were transformed into age- and sex-adjusted z-scores. Three linear regression models were performed, including adjustment for confounders in a stepwise manner. Measurements at age 3 months, before weaning, were used to consider reverse causality.
  
  
  RESULTS
  Almost three-quarters (72.9%) of infants were weaned before age 6 months. Age at weaning of 3.0-7.0 months was inversely associated with weight and length (but not with body mass index) at 12 months (both P ≤ .01, adjusted for maternal and demographic factors). These associations were attenuated after adjustment for type of milk feeding and weight or length at age 3 months (before weaning). Rapid weight gain between 0 and 3 months predicted subsequent earlier age at weaning (P = .01). Our systematic review identified 2 trials, both reporting null effects of age at weaning on growth, and 15 observational studies, with 10 reporting an inverse association between age at weaning and infant growth and 4 reporting evidence of reverse causality.
  
  
  CONCLUSIONS
  In high-income countries, weaning between 3 and 6 months appears to have a neutral effect on infant growth. Inverse associations are likely related to reverse causality.
authors.affiliation: Department of Public Health and Primary Care, University of Cambridge, Cambridge, United Kingdom; School of Medicine, University of California San Francisco, San Francisco, CA.
authors.forename: Brennan
authors.initials: B
authors.lastname: Vail
authors.affiliation: Department of Pediatrics, University of Cambridge, Cambridge, United Kingdom.
authors.forename: Philippa
authors.initials: P
authors.lastname: Prentice
authors.affiliation: Department of Pediatrics, University of Cambridge, Cambridge, United Kingdom.
authors.forename: David B
authors.initials: DB
authors.lastname: Dunger
authors.affiliation: Department of Pediatrics, University of Cambridge, Cambridge, United Kingdom.
authors.forename: Ieuan A
authors.initials: IA
authors.lastname: Hughes
authors.affiliation: Department of Pediatrics, University of Cambridge, Cambridge, United Kingdom.
authors.forename: Carlo L
authors.initials: CL
authors.lastname: Acerini
authors.affiliation: Department of Pediatrics, University of Cambridge, Cambridge, United Kingdom; Medical Research Council Epidemiology Unit, Institute of Metabolic Science, Cambridge, United Kingdom. Electronic address: ken.ong@mrc-epid.cam.ac.uk.
authors.forename: Ken K
authors.initials: KK
authors.lastname: Ong
mesh_terms: D000886:Anthropometry; D001942:Breast Feeding; D002657:Child Development / Q000502:physiology*; D015331:Cohort Studies; D005260:Female; D006801:Humans; D007223:Infant; D016014:Linear Models; D008297:Male; D011446:Prospective Studies; D006113:United Kingdom; D014886:Weaning