Postnatal BMI changes in children with different birthweights: A trial study for detecting early predictive factors for pediatric obesity.

The purpose of this study was to clarify the degree of early postnatal growth by birthweight and detect early predictive factors for pediatric obesity. Body mass index (BMI) and degree of obesity were examined in children in the fourth year of elementary school and second year of junior high school. Their BMI at birth and three years of age were also examined. Based on birthweight, participants were divided into three groups: low (< 2500 g), middle (2500-3500 g), and high (> 3500 g). Furthermore, according to the degree of obesity, they were divided into two groups: obese (20% ≤) and non-obese (20% >). The change of BMI from birth to three years of age (ΔBMI) showed a strong inverse relationship with birthweight and was significantly different among the three birthweight groups (low > middle > high). The ΔBMI and BMI at three years of age were higher in obese than in non-obese children and showed significant positive correlations with the degree of obesity. Early postnatal growth might be determined by birthweight and was higher in obese than in non-obese children. The ΔBMI from birth to three years of age and BMI at age of three years could be predictive factors for pediatric obesity.