Associations between birthweight and overweight and obesity in school-age children.

BACKGROUND: Relationships between birthweight and future obesity risk remain unclear.

OBJECTIVE: To assess associations between birthweight and later obesity in a nationally representative cohort of early school-aged children.

METHODS: We used linear and logistic regression to evaluate 10 186 term- or preterm children in the Early Childhood Longitudinal Study-Kindergarten Cohort 2011 for relationships between birthweight and later obesity and change in BMI z-score from kindergarten-to-second grade. All analyses were adjusted for sex, race/ethnicity, parental education and household income.

RESULTS: Compared to children born normal birthweight (NBW), high birthweight (HBW) term children and large-for-gestational-age (LGA) preterm children had significantly greater BMI z-scores from kindergarten-to-second grade (p < 0.001). Term children born HBW had higher odds of obesity by kindergarten (adjusted odds ratios [aOR] 1.91, p < 0.0001). Among preterm children, odds of obesity was higher among LGA children starting in first grade (aOR 2.34, p < 0.05) and among small-for-gestational age children in second grade (aOR 2.26, p < 0.05). Compared to NBW children, HBW children had greater change in BMI z-score between kindergarten-first grade (p < 0.01).

CONCLUSIONS: High birthweight term and LGA preterm children had increased adjusted odds of obesity in school-age compared to their NBW counterparts. Physicians may provide counselling early in life for families of large infants to help prevent future obesity.