Features of the 2000 & 2022 CDC Growth Charts

The data used to construct the CDC growth charts included a nationally representative reference population during 1963-1994 of children and teens aged 2 to 20 years. Statistical smoothing methods were used to fit the data from national surveys to create smooth curves.

Read more about statistical smoothing procedures [PDF – 5.4MB]

Read more about the construction of LMS parameters for the CDC 2000 growth charts. [PDF – 88KB]

Significant features of the CDC growth charts include:

• BMI-for-age charts for children and teens aged 2 to 20 years.
• Stature-for-age and weight-for-age charts for children and teens aged 2 to 20 years.
• Smoothed percentile curves and corresponding z-scores are used to evaluate the growth of children.
  • Percentiles are the most commonly used clinical indicator to assess growth patterns of individual children in the United States. Percentiles rank the position of an individual by indicating what percent of the reference population the individual would equal or exceed. For example, on the weight-for-age growth charts, a 5-year-old girl whose weight is at the 25th percentile, weighs the same or more than 25 percent of the reference population of 5-year-old girls, and weighs less than 75 percent of the 5-year-old girls in the reference population (Kuczmarski et al., 2002).
  • A z-score is a statistical measure that indicates how far a given value is from the mean (or average). Z-scores have a direct relationship with percentiles, and a conversion can occur in either direction (using a standard normal distribution table). For every z-score there is a corresponding percentile and vice versa (Kuczmarski et al., 2002).

Significant features of the 2022 CDC Extended BMI-for-age growth charts

• Include four additional percentile curves above the 95^th percentile: 98^th, 99^th, 99.9^th, and 99.99^th percentiles.
• Can plot BMI values up to 60 kg/m2.
• Visually display the threshold for severe obesity at 120% of the 95^th percentile
• Feature colored shading that provides a visual aid for clinicians when discussing very high BMI with families.
• Unlike other options for monitoring growth in children with very high BMI which reflect theoretical or statistical extrapolations, the 2022 CDC extended BMI-for-age growth charts are based on more recent data from a nationally representative sample of children and adolescents with obesity.
• Prior to development of the new extended percentiles, it was difficult to interpret percentiles or z-scores beyond the 97^th percentile. Curves beyond the 97^th can only be mathematically created because there were too few children beyond the 97^th percentile in the 1963-1994 reference population to create percentile curves based on real data. In the extended charts, the newly added percentiles above the 95^th percentile are based on more recent nationally representative data for children with obesity. The extended z-scores associated with these new percentiles are more meaningful and accurately reflect patterns among real children at extremely high BMI values.
• With very high BMI values above the 99^th percentile, the z-score may be an easier number for clinicians, patients, and families to understand. For example, the value of z-score=1 is nearly equivalent to the 85^th percentile–the threshold for overweight status. A z-score of 4 is equivalent to the 99.9^th percentile, but the z-scores of 4 and 1 may easier to convey to patients and families compared to 99.9^thand 85^th percentiles.

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