Experimental growth chart blending CDC’s and WHO’s data improves clinic’s evaluation of childhood growth
Particularly for children between the ages of 18-months and 2-years, the CDC’s growth chart overidentified drops in both weight and BMI Z-scores compared to experimental growth chart.
Journal: Pediatrics (IF 6.4)
Article Year: 2025
Researchers created new growth charts that gradually transition (i.e., combine) weight-for-age, length/height-for-age, and body mass index (BMI)-for-age data from the World Health Organization (WHO) and Centers for Disease Control’s (CDC) for children between the ages of 2 and 5 years. Historically, clinicians use the WHO growth charts to assess growth in children less than 2 years of age before switching to the CDC charts otherwise used for the general population. This study was performed because upon switching charts, clinicians may detect a drop in a child’s z-score that is artifactual rather than clinically relevant; this is nonetheless distracting and may lead to the overidentification of slow weight gain, causing unnecessary parental anxiety and potentially distracting clinicians from real concerns. In contrast, the charts designed by these Daymont, et. al produced less artifactual change and thus may reduce the number of false alarms.
The math used by Daymont, et. al is beyond the scope of this summary but basically uses z-scores and age ranges to produce a new z-score value somewhere between that calculated by the CDC and that calculated by WHO. Most notably, when analyzing growth between the ages of 1.5 and 2 years (the age ranges with the largest discrepancies when comparing CDC and WHO z-scores), the traditional CDC-recommended charts show a much greater change in a child's z-score compared to the new gradual charts. Most notably, the average change in BMI z-score was a drop of 0.59 with the CDC charts, but only a drop of 0.09 with the gradual charts. Similarly, the average weight z-score had a greater drop with the CDC charts (a drop of 0.35) than with the gradual charts. For weight, the difference was somewhat less stark: 6% of children had a large drop with the CDC charts, compared to less than 1% with the gradual charts.
Comment: The use of growth charts varies widely by practice and clinician. Numerous methods for smoothing the discrepancies between data exist but are not necessarily used; while this method offer a valuable alternative for clinicians and researchers seeking to avoid the pitfalls of the abrupt switch at age 2, incorporations by EHRs will largely dictate whether assessments of growth like this one are used daily. Further, this study only assessed the variance of Z-score without correlating it with health outcomes. Additionally complicating comparisons between the CDC and WHO data is the fact that at their conceptions, the CDC charts only assessed the growth of formula-fed children who may gain weight faster than breastfed children whereas the WHO’s data is derived from breastfed children. While the widely-used CDC-recommended charts may be a better fit for 2-year-olds by some criteria and facilitate better communication between clinicians and researchers, the gradual charts provide a smoother, more accurate picture of growth, especially when tracking changes over time.
To read more: Daymont C et al. Creation and Evaluation of New Growth Charts With a Gradual Transition From WHO to CDC Values. Pediatrics 2025 8 18; 156 (3). (https://doi-org.libproxy.unm.edu/10.1542/peds.2025-070697)