The preventive effect of breast-feeding for longer than 6 months on early pubertal development among children aged 7-9 years in Korea.

OBJECTIVE: The present study was performed to investigate whether breast-feeding is associated with early pubertal development among children 7-9 years old in Korea. DESIGN: Children were divided into those who did and did not receive breast-feeding for 6 months or longer in accordance with the recommendations of the WHO. Pubertal status was determined by clinical examination using Tanner staging. SETTING: Prospective observational study. SUBJECTS: We conducted a follow-up study of children aged 7-9 years in 2011 who had taken part in the Ewha Birth & Growth Cohort study. RESULTS: Fifty (22.8%) of the total of 219 children were in early puberty with the proportion being slightly higher for girls (24.1%) than boys (21.4%). Children who had entered early puberty were taller weighed more and had a higher concentration of insulin-like growth factor 1. Moreover the change in weight Z-score from birth to follow-up was significantly lower in children who were breast-fed than in those who were not (weight Z-score change: 0.32 (sd 1.59) v. 0.77 (sd 1.61) respectively P=0.04). Comparison of breast-feeding by puberty status indicated a preventive association with early puberty in children who were breast-fed for 6 months or longer (OR=0.37; 95% CI 0.18 0.74). This association remained significant after adjustment for relevant covariates. CONCLUSIONS: These results demonstrate a beneficial association between breast-feeding and early pubertal development especially in those breast-fed for 6 months or longer. The study suggests that interventions would need to start early in life to prevent early pubertal development.