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Prader-Willi Syndrome (PWS) and the WHO Growth ChartsOverview In early 2006, the World Health Organization (WHO) released new child growth charts that differ significantly from the U.S. Center for Disease Control (CDC) charts used by most U.S. doctors. The new charts are based on a WHO study tracking 8,000 children in six countries from birth to age five. All the children were breastfed for the first year of life and came from healthy homes. The study found that, regardless of ethnicity, all of the children grew very similarly up to age 5, and the new WHO charts are based on this "optimal growth" curve. The CDC charts, in contrast, show how an individual child compares with the average U.S. child - regardless of whether that "average" rate of growth is actually healthy or not. That is becoming an increasingly important issue because the rates of excessive weight and obesity in U.S. children are rising. Less than 40% of U.S. babies are exclusively breastfed for six months. Breastfed babies tend to be leaner and perhaps because of that, the WHO curve differs significantly from the CDC charts and categorizes more U.S. babies as overweight. For example, the average one-year-old female baby on the CDC chart weighs a bit under 21 pounds, while the optimal 1-year-old girl on the WHO chart weighs 19.8 pounds. That difference may be significant because studies show breastfed babies tend to have a lower risk of obesity later in life. The CDC, American Academy of Pediatrics and other health organizations have begun a series of meetings to discuss the WHO charts and whether to make changes to the CDC charts. In the meantime, all parents might find it informative to assess their babies' and children's growth on the new WHO charts, compared to the CDC charts. For parents of children with Prader-Willi Syndrome, the WHO charts are relevant to both the "failure to thrive" stage in the first year or so, as well as the second stage when hyperphagia develops. Babies in the first stage will typically chart at somewhat higher percentiles on the WHO charts compared to the CDC charts, which may be reassuring to those struggling to maintain adequate nutritional status and growth in an infant with little interest in feeding. However, older children will also track in somewhat higher percentiles on the WHO charts. Charts The new WHO charts can be downloaded from WHO in pdf format. In addition, I have converted the percentile versions to jpg format and posted them below for easy viewing, printing and/or saving to your computer. Growth can be manually plotted on printed charts or the jpg format charts can be opened in any photo or graphics editing program for plotting growth points (a chart with sample data plots is available below). Spreadsheet The WHO growth charts use metric measurements (centimeters and kilograms). In addition, WHO uses a different formula for calculating Body Mass Index (BMI) than is typically used in the U.S. The WHO formula for BMI is - weight (in kilograms) / height (in meters)2
U.S. to metric conversion utilities such as those at onlineconversion.com can be used to calculate the data points. Alternatively, spreadsheet templates for converting and calculating the data (length in centimeters, weight in kilograms, meters2 and BMI) for plotting on the charts are available for downloading in Microsoft Excel and Open Office Calc format:
A screenshot of the spreadsheet can be seen below. Note that the spreadsheet was developed in Open Office Calc and exported to xls format for the Excel version. I don't have Excel, so I can't vouch for how well the xls version will work in Excel. Open Office is a free, open source office suite that contains the usual office suite programs (word processing, spreadsheet, etc.) and is available for download at openoffice.org. As always, feedback is welcomed. Who Growth Charts
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