Discordance in the assessment of prepregnancy weight status of adolescents: a comparison between the Centers for Disease Control and Prevention sex- and age-specific body mass index classification and the Institute of Medicine-based classification used for maternal weight gain guidelines.

In 1990, the Institute of Medicine (IOM) issued maternal weight gain guidelines to prevent intrauterine growth retardation based on adult prepregnancy body mass index (BMI; calculated as kg/m(2)). A recent IOM report, however, expressed concerns regarding application of adult criteria (prepregnancy BMI and gestational weight gain recommendations) to categorize pregnant adolescents. To draw attention to the assessment of prepregnancy weight status among adolescents and to its potential clinical implications, we estimated the percent discordance between the Centers for Disease Control and Prevention (CDC) BMI-for-age categories currently used for the assessment of adolescent weight status (underweight, healthy weight, at risk of overweight, and overweight) and the IOM-based categories (low, average, high, obese) among 11,656 adolescents 12 to 20 years old from a birth registry. Approximately one quarter of all adolescents in this sample and 40% of young adolescents (12 to 15 years old) were "misclassified." Among healthy weight adolescents, 23.4% and 0.6% were "misclassified" as low and high, respectively, by IOM categories. Among at-risk of overweight adolescents, 13.5% and 26.9% were "misclassified" as average and obese by IOM categories. Based on our findings, we suggest that adolescent prepregnancy weight categories be assessed using the CDC BMI charts and to examine gestational weight gain distributions exclusively among adolescents according to the CDC BMI categories.