Breast-feeding and mental and motor development at 51/2 years

Ambul Pediatr. Mar-Apr 2006;6(2):65-71. doi: 10.1016/j.ambp.2005.11.003.


Objective: Breast-feeding is associated with better child development outcomes, but uncertainty remains primarily due to the close relationship between breast-feeding and socioeconomic status. This study assesses the issue in a low socioeconomic status sample where breast-feeding was close to universal.

Methods: Seven hundred eighty-four Chilean children were followed longitudinally from infancy. All but four were initially breastfed, 40% nursed beyond 12 months, and infant growth was normal. Child development was assessed at 5(1/2) years by a cognitive, language, and motor test battery. The duration of breast-feeding as the sole milk source was analyzed as a continuous variable, adjusting for a comprehensive set of background factors.

Results: The relationship between breast-feeding and most 5(1/2)-year developmental outcomes was nonlinear, with poorer outcome for periods of breast-feeding as the sole milk source for <2 months or >8 months--statistically significant for language, motor, and one comprehensive cognitive test, with a suggestive trend for IQ.

Conclusions: The observed nonlinear relationships showed that breast-feeding as the sole milk source for <2 months or >8 months, compared with 2-8 months, was associated with poorer development in this sample. The latter finding requires replication in other samples where long breast-feeding is common and socioeconomic status is relatively homogeneous.

Publication types

  • Comparative Study
  • Research Support, N.I.H., Extramural

MeSH terms

  • Analysis of Variance
  • Breast Feeding*
  • Child Development / physiology*
  • Child, Preschool
  • Cognition / physiology*
  • Cohort Studies
  • Female
  • Humans
  • Infant
  • Infant, Newborn
  • Intelligence Tests
  • Longitudinal Studies
  • Male
  • Mental Processes / physiology
  • Psychomotor Performance / physiology*
  • Risk Assessment
  • Socioeconomic Factors
  • Time Factors