Assessing Growth Using the WHO Growth Charts
- Use recommended protocols to measure the weight and recumbent length of the child accurately. Record the measurements correctly.
- Accurately measuring and recording this information is critical for growth charts to be used as an effective screening tool.
- Calculating age correctly is also critical for accurate growth determinations and interpretations.
- Plot these measurements on the appropriate WHO growth chart.
- Use the percentile lines on the chart to assess body size and growth and to monitor growth over time.
The World Health Organization (WHO) recommends cutoff values of +2 standard deviations, which correspond to the 2.3rd and 97.7th percentiles, to define abnormal growth.1
- For the WHO growth charts modified by CDC, these cutoff values are labeled as the 2nd percentile and the 98th percentile.
- Infants and children with a weight-for-length that is less than the 2nd percentile are classified as low weight-for-length.
- Infants and children with a length-for-age that is less than the 2nd percentile are classified as having short stature.
- Infants and children with a weight-for-length that is higher than the 98th percentile are classified as high weight-for-length.
WHO Percentile Cutoff Values Differ from Traditional CDC Cutoff Values
The cutoff values for the 2nd and 98th percentiles used in the WHO growth standard charts are different from those used in the CDC growth references chart. CDC uses the 5th and 95th percentiles. Different methods are used to create the WHO and CDC charts.
- Historically, CDC used the 5th percentile to define shortness and low weight-for-length, and the 95th percentile was used to define high weight-for-length.
- Using the WHO growth chart cutoff values indicates a change in clinical protocol.
- Theoretically, children in the WHO population would be expected to be healthy. Thus, more extreme cutoff values are more appropriate to define the extremes of growth of children rather than the values used in the CDC growth reference.2
The WHO growth standard charts are intended to reflect normal child growth under optimal environmental conditions.
- Although many children in the United States do not experience the optimal environmental, behavioral, or health conditions specified in the WHO Multicenter Growth Reference Study, the WHO growth standard charts are intended for use with children younger than aged 24 months because they represent optimal growth.
1World Health Organization. WHO Child Growth Standards: Length/Height-for-Age, Weight-for-Age, Weight-for-Length, Weight-for-Height and Body Mass Index-for-Age: Methods and Development. Geneva, Switzerland: World Health Organization; 2006.
2Mei Z, Ogden CL, Flegal KM, Grummer-Strawn LM. Comparison of the prevalence of shortness, underweight, and overweight among US children aged 0 to 59 months by using the CDC 2000 and the WHO 2006 growth charts. J Pediatr. 2008;153(5):622-628.