title: Do population-based interventions widen or narrow socioeconomic inequalities? The case of breastfeeding promotion.
abstract: BACKGROUND
  Despite numerous population-based randomized intervention trials, the impact of such interventions on socioeconomic inequalities has rarely been examined. We used data from a large cluster-randomized trial to assess the impact of a breastfeeding promotion intervention on socioeconomic inequalities in breastfeeding (exclusivity and duration) and in child cognitive ability at early school age.
  
  
  METHODS
  The Promotion of Breastfeeding Intervention Trial (PROBIT) randomized 31 Belarusian maternity hospitals and their affiliated polyclinics either to receive a breastfeeding promotion intervention modelled on the WHO/UNICEF Baby-Friendly Hospital Initiative or to continue the standard practices in effect at the time of randomization. We estimated and compared inequalities in discontinuation of exclusive breastfeeding before 3 months and of any breastfeeding before 12 months and in child verbal IQ at age 6.5 years, across maternal education strata between the two intervention arms.
  
  
  RESULTS
  Socioeconomic inequalities in discontinuing exclusive breastfeeding before 3 months were negligible in the control group. However, graded inequalities by maternal education emerged in the intervention group {relative risk [RR] = 1.12 [95% confidence interval (CI): 1.04, 1.20] for partial university and RR = 1.20 [95% CI: 1.11, 1.31] for secondary education or less vs complete university; risk difference [RD] = 0.06 [95% CI: 0.03, 0.09] and 0.10 [95% CI: 0.06, 0.14], respectively}. For discontinuing any breastfeeding before 12 months, small socioeconomic gradients in the control group were widened in the intervention group (RR = 1.04 and 1.16, respectively, for mothers with secondary education or less). Despite these differential effects on breastfeeding, however, we observed a small, nonsignificant reduction in socioeconomic inequalities in child verbal IQ at age 6.5 years.
  
  
  CONCLUSIONS
  A population-based intervention to promote breastfeeding slightly widened socioeconomic inequalities in breastfeeding but not those in child cognitive ability.
authors.affiliation: Department of Pediatrics, Research Institute of McGill University Health Centre, Montreal, Canada and Department of Epidemiology, Biostatistics, and Occupational Health, McGill University, Montreal, Canada seungmi.yang@mail.mcgill.ca.
authors.forename: Seungmi
authors.initials: S
authors.lastname: Yang
authors.affiliation: Department of Pediatrics, Research Institute of McGill University Health Centre, Montreal, Canada and Department of Epidemiology, Biostatistics, and Occupational Health, McGill University, Montreal, CanadaDepartment of Pediatrics, Research Institute of McGill University Health Centre, Montreal, Canada and Department of Epidemiology, Biostatistics, and Occupational Health, McGill University, Montreal, Canada.
authors.forename: Robert W
authors.initials: RW
authors.lastname: Platt
authors.affiliation: Department of Pediatrics, Research Institute of McGill University Health Centre, Montreal, Canada and Department of Epidemiology, Biostatistics, and Occupational Health, McGill University, Montreal, Canada.
authors.forename: Mourad
authors.initials: M
authors.lastname: Dahhou
authors.affiliation: Department of Pediatrics, Research Institute of McGill University Health Centre, Montreal, Canada and Department of Epidemiology, Biostatistics, and Occupational Health, McGill University, Montreal, CanadaDepartment of Pediatrics, Research Institute of McGill University Health Centre, Montreal, Canada and Department of Epidemiology, Biostatistics, and Occupational Health, McGill University, Montreal, Canada.
authors.forename: Michael S
authors.initials: MS
authors.lastname: Kramer
mesh_terms: D001942:Breast Feeding; D002648:Child; D002657:Child Development; D003071:Cognition; D005260:Female; D005500:Follow-Up Studies; D006293:Health Promotion / Q000379:methods*; D054624:Health Status Disparities; D006801:Humans; D007223:Infant; D007231:Infant, Newborn; D007361:Intelligence Tests; D008297:Male; D009035:Mothers; D012923:Social Class; D012959:Socioeconomic Factors; D016896:Treatment Outcome
keywords: Health inequalities; breastfeeding; cognitive functioning; randomized intervention trials