title: Infant growth and health outcomes associated with 3 compared with 6 mo of exclusive breastfeeding.
abstract: BACKGROUND
  Opinions and recommendations about the optimal duration of exclusive breastfeeding have been strongly divided, but few published studies have provided direct evidence on the relative risks and benefits of different breastfeeding durations in recipient infants.
  
  
  OBJECTIVE
  We examined the effects on infant growth and health of 3 compared with 6 mo of exclusive breastfeeding.
  
  
  METHODS
  We conducted an observational cohort study nested within a large randomized trial in Belarus by comparing 2862 infants exclusively breastfed for 3 mo (with continued mixed breastfeeding through >/= 6 mo) with 621 infants who were exclusively breastfed for >/= 6 mo. Regression to the mean, within-cluster correlation, and cluster- and individual-level confounding variables were accounted for by using multilevel regression analyses.
  
  
  RESULTS
  From 3 to 6 mo, weight gain was slightly greater in the 3-mo group [difference: 29 g/mo (95% CI: 13, 45 g/mo)], as was length gain [difference: 1.1 mm (0.5, 1.6 mm)], but the 6-mo group had a faster length gain from 9 to 12 mo [difference: 0.9 mm/mo (0.3, 1.5 mm/mo)] and a larger head circumference at 12 mo [difference: 0.19 cm (0.07, 0.31 cm)]. A significant reduction in the incidence density of gastrointestinal infection was observed during the period from 3 to 6 mo in the 6-mo group [adjusted incidence density ratio: 0.35 (0.13, 0.96)], but no significant differences in risk of respiratory infectious outcomes or atopic eczema were apparent.
  
  
  CONCLUSIONS
  Exclusive breastfeeding for 6 mo is associated with a lower risk of gastrointestinal infection and no demonstrable adverse health effects in the first year of life.
authors.affiliation: Department of Pediatrics, McGill University Faculty of Medicine, Montreal. michael.kramer@mcgill.ca
authors.forename: Michael S
authors.initials: MS
authors.lastname: Kramer
authors.forename: Tong
authors.initials: T
authors.lastname: Guo
authors.forename: Robert W
authors.initials: RW
authors.lastname: Platt
authors.forename: Zinaida
authors.initials: Z
authors.lastname: Sevkovskaya
authors.forename: Irina
authors.initials: I
authors.lastname: Dzikovich
authors.forename: Jean-Paul
authors.initials: JP
authors.lastname: Collet
authors.forename: Stanley
authors.initials: S
authors.lastname: Shapiro
authors.forename: Beverley
authors.initials: B
authors.lastname: Chalmers
authors.forename: Ellen
authors.initials: E
authors.lastname: Hodnett
authors.forename: Irina
authors.initials: I
authors.lastname: Vanilovich
authors.forename: Irina
authors.initials: I
authors.lastname: Mezen
authors.forename: Thierry
authors.initials: T
authors.lastname: Ducruet
authors.forename: George
authors.initials: G
authors.lastname: Shishko
authors.forename: Natalia
authors.initials: N
authors.lastname: Bogdanovich
mesh_terms: D000328:Adult; D001942:Breast Feeding; D015331:Cohort Studies; D004522:Educational Status; D005260:Female; D005767:Gastrointestinal Diseases / Q000453:epidemiology / Q000517:prevention & control; D006128:Growth; D006801:Humans; D015994:Incidence; D007223:Infant; D008297:Male; D012141:Respiratory Tract Infections / Q000453:epidemiology / Q000517:prevention & control; D013997:Time Factors; D015430:Weight Gain