Duration of breast-feeding and Bayley's mental developmental index at 1 year of age

Objective: To examine the association between duration of exclusive breast-feeding and developmental indices in initially breast-fed infants at 1 year of age. Methodology: A cohort of 96 healthy term infants, aged between 10 and 14 months, were recruited from public immunization clinics and child care centres in southern metropolitan Adelaide. Infants were assessed using the Bayley Scales of Infant Development (Mental and Psychomotor Developmental Indices) within 2 weeks of enrolment. Information regarding duration of breast-feeding was provided retrospectively by the mothers of the infants. Duration of exclusive breast-feeding and sociodemographic variables were used as independent variables to determine their effects on development. Results: Due to a significant interaction between duration of breast-feeding and gender on mental development scores, separate regression models for boys and girls were explored. Duration of breast-feeding significantly predicted mental development scores for boys (partial r² = 0.14, P < 0.005), but not for girls. Duration of breast-feeding did not predict psychomotor development scores. Conclusions: These findings deserve further examination in large, prospective studies.