Sex non-specific growth charts and potential clinical implications in the care of transgender youth

Introduction The Centers for Disease Control and Prevention (CDC) and World Health Organization (WHO) created separate growth charts for girls and boys because growth patterns and rates differ between sexes. However, scenarios exist in which this dichotomizing girls versus boys approach may not be ideal, including the care of non-binary youth or transgender youth undergoing transitions consistent with their gender identity. There is therefore a need for growth charts that age smooth differences in pubertal timing between sexes to determine how youth are growing as children versus girls or boys (e.g., age- and sex-neutral, compared to age- and sex-specific, growth charts).Methods Employing similar statistical techniques and datasets used to create the CDC 2000 growth charts, we developed age-adjusted, sex non-specific growth charts for height, weight, and body mass index (BMI), and z-score calculators for these parameters. Specifically, these were created using anthropometric data from five US cross-sectional studies including National Health Examination Surveys II-III and National Health and Nutrition Examination Surveys I-III. To illustrate contemporary clinical practice, we overlaid our charts on CDC 2000 girls and boys growth charts.Results 39,119 youth 2-20 years old (49.5% female; 66.7% non-Hispanic White; 21.7% non-Hispanic Black) were included in the development of our growth charts, reference ranges, and z-score calculators. Respective curves were largely superimposable through around 10 years of age after which, coinciding with pubertal onset timing, differences became more apparent.Discussion We conclude that age-adjusted, sex non-specific growth charts may be used in clinical situations such as transgender youth in which standard girls versus boys growth charts are not ideal. Until longitudinal auxological data are available in these populations, our growth charts may help to assess a transgender youth's growth trajectory and weight classification, and expectations surrounding these.

Automated summary

The CDC and WHO have separate growth charts for boys and girls, but there is a need for gender-neutral growth charts that can accommodate non-binary or transgender youth. Using statistical techniques and data from US surveys, the researchers developed age-adjusted, sex non-specific growth charts for height, weight, and BMI. These charts can be useful in assessing growth trajectories and weight classifications for transgender youth.