Creation and Evaluation of New Growth Charts With a Gradual Transition From WHO to CDC Values

BACKGROUND AND OBJECTIVES At age 2 years, the Centers for Disease Control and Prevention (CDC) recommends switching from the World Health Organization (WHO) Growth Standards to the CDC 2000 Growth Reference. This abrupt switch may affect growth assessment, such as causing a clinically important change in growth z score in a child with a stable growth pattern. We sought to create growth charts that gradually transition between WHO and CDC and to evaluate their impact on growth assessment of young children using real-world data. METHODS We iteratively developed methods to create new charts for body mass index (BMI)-, weight-, and length/height-for-age. We performed a retrospective cohort study comparing the mean change in z scores for these parameters between 1.5 and 2 years for the CDC-recommended vs the new, gradually transitioned (gradual) charts. We also compared the prevalence of a large change in z score: <−1 (drop) or >1 (rise). RESULTS We transitioned between the charts using a weighted average from ages 2 to 5 years. In 7429 children, there was a large decrease in mean body mass index-for-age z score (BMIz) and weight-for-age z score (WTz) in the CDC-recommended charts (BMIz −0.59, WTz −0.35) that was not seen in the gradual charts (BMIz −0.09, WTz −0.01). Correspondingly, using the CDC-recommended charts, the proportion with a drop in BMIz or WTz was much higher for the CDC-recommended (BMIz 28.3%, WTz 6.0%) than the gradual charts (BMIz 11.6%, WTz 0.85%). CONCLUSIONS We created growth charts that gradually transition between WHO and CDC and may reduce overidentification of slow weight gain. These charts may be useful in clinical care and research.