Nutritional assessment of pregnant adolescents: comparison of two popular classification systems

The objective of this study was to assess the degree of concordance between two popular classification systems [the Centers for Disease Control and Prevention (CDC)-2000 and the Institute of Medicine (IOM)-2009] used to categorise the nutritional status of pregnant adolescents. This cross-sectional study involved 327 pregnant adolescents (10-19 years) booking for antenatal care at a single public maternity in SAo Paulo, Brazil. Participants were classified into one of four categories, by both systems according to their pre-pregnancy body mass index and age. The CDC-2000 system classified significantly fewer pregnant adolescents as underweight (3.7% vs. 12.5%, P<0.0001) and significantly more adolescents as normal-weight (86.8% vs. 75.6%, P=0.0003) than the IOM-2009 system. The distribution of the adolescents in the two systems differed significantly. The global rate of discordance was 13.5%. The overall concordance between the two systems was marginally good (K=0.63), being moderate for younger (<16 years) adolescents (K=0.52). Approximately one in every seven pregnant adolescent would be classified in a non-corresponding category if the IOM-2009 classification was used instead of the CDC-2000 classification. The IOM-2009 nutritional classification, which does not take into account age and gender, tends to overestimate the proportion of underweight adolescents, especially in the younger-age group. The use of this classification system can lead to recommendations of higher gestational weight gain in a substantial proportion of pregnant adolescents, which could predispose to post-partum weight retention and future obesity.