Overview
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 or not that “average” rate of growth is actually healthy. 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 for printing and the child’s growth can be manually plotted on printed charts. The WHO charts use metric measurements (centimeters and kilograms) and U.S. to metric conversion utilities such as those at onlineconversion.com can be used to calculate the data points for plotting. Note that WHO also uses a different formula for calculating Body Mass Index (BMI) than is sometimes used in the U.S. The WHO formula for BMI is -
weight (in kilograms) / height (in meters)2