Association of perinatal factors and obesity in 6-to 8-year-old Chilean children

Background It has been reported in Chile that obesity figures in children of 6- to 8-years-old are associated with height for age. We studied the possible influence of perinatal variables on obesity at 6- to 8-years-old controlling for height for age. Methods All children with 68 years of age attending first grade in public primary schools of Chile in year 2005 were included. An historical cohort design was used and perinatal information collected at birth was obtained from the National Registry. Obesity was defined as BMI >= 95th percentile of the CDC reference. Comparisons of obesity prevalence in contingency tables used the chi-squared test. Logistic regression was used to calculate ORs for obesity risk in univariate and multivariate categorical models. Results Out of 167 494 initial subjects, 153 536 children entered the study. Obesity prevalence was higher in stunted and in tall for age children (20.1 and 26.0% respectively) compared with those with normal height for age (17.3) (P < 0.0001). Adjusted odds ratio for perinatal information showed that infants born male, premature and short in length at birth were more prone to obesity than their counterparts. However, birth weight (BW) had a stronger positive influence on obesity risk. Conclusions Taller and stunted children had higher obesity risk than normal height for age children. This association did not change when controlling for the influence of perinatal data; post-natal influences may be playing an independent role. Although BW was linearly associated with obesity, short and premature babies also had a higher risk of obesity.