Association of early pregnancy body mass index and children's birth weight with risk of being overweight in childhood.

OBJECTIVES: To examine the potential effects of mothers' early pregnancy body mass index (BMI) and children's birth weight on childhood overweight/obesity at 1-6 years of age.

METHODS: We performed a cohort study in Tianjin, China, using the health care records from the Tianjin maternal and child health care system with 36 719 mother-child pairs from early pregnancy to children at 6 years of age. Logistic regression analyses were used to assess the single and joint associations of maternal early pregnancy BMI and children's birth weight with the risks of children being overweight at 1-6 years of age in multivariable-adjusted models.

RESULTS: Both maternal early pregnancy BMI and children's birth weight were positively associated with the risk of children being overweight at 1-6 years of age. Compared with children who were born to normal weight mothers and had low or normal birth weight (NBW; birth BMI < 85%), higher risks of being overweight at 1-6 years were found among children with low or NBW who were born to overweight mothers, and children with high NBW (BMI ≥ 85%) or macrosomia who were born to normal weight or overweight mothers. Lower risks of being overweight were found among those with low birth weight who were born to normal weight mothers.

CONCLUSIONS: Maternal early pregnancy BMI may play a more important role than children's birth weight in the risk of being overweight from 4 to 6 years of age. Children with high or NBW need to be given more attention to prevent excessive weight gain.