Accuracy of maternal reports of pre-schoolers' weights and heights as estimates of BMI values.

Data is lacking on the reliability of weight and height for young children as reported by parents participating in population-based studies. We analysed the accuracy of parental reports of children's weights and heights as estimates of body mass index, and evaluated the factors associated with the misclassification of overweight and obese children. Analyses were conducted on a population-based birth cohort of 1549 4-year-old children from the province of Québec (Canada) in 2002. Mothers reported weights and heights for the children as part of the regular annual data collection. Within the following 3 months, children's weights and heights were measured at home as part of a nutrition survey. This study indicates that mothers overestimate their children's weight more than their height, resulting in an overestimation of overweight children of more than 3% in the studied population. Only 58% of the children were reported as overweight/obese with reported values. Maternal misreporting is more important for boys than girls, and for low socioeconomic status children compared with high socioeconomic status children. Research on the prevalence of overweight and obesity has often used self-reported measures of height and weight to estimate BMI. However, the results emphasize the importance of collecting measured data in childhood studies of overweight and obesity at the population level.