The CDC just announced that it is now recommending that health care providers use the 2006 WHO growth charts for children up to 24 months instead of the 2000 CDC charts. Here is the announcement, dated today. The U.K. health system adopted these charts last year.
Not sure what the WHO growth charts are? Here's the scoop, from a post I wrote in 2007:
Until recently the growth charts used by pediatricians were based on a sample of all formula-fed, all Caucasian babies born between 1929 and 1975 in Ohio. These babies also often started solid foods before four months. I recently learned that these charts were used around the world to chart babies' growth. More recently, in 2000, the CDC released a chart using a mixed sample of breastfed and formula-fed infants. It yielded similar problems (explained below).
Research from the early 1990's demonstrated that breastfed and formula-fed babies have different growth patterns. The most significant differences are that breastfed babies grow faster than formula-fed babies in the first few months, and then "lean out" compared to formula-fed babies between 3 and 12 months.
So, if you try to chart a breastfed baby's growth using the formula-fed charts, you might see a baby who is falling off of the curve after the first 2 months. This sometimes resulted in recommendations that mothers supplement with formula. It also meant that formula-fed babies who were experiencing excessive weight gain in later months - and at risk of later overweight and obesity - were viewed as normal and no interventions were recommended.
The new WHO charts use a sample of nearly 9,000 babies who were exclusively or nearly exclusively breastfed for the first six months. The study methodology is described in detail here. To me, the most interesting finding is that, when factors like malnutrition, socio-economic status, and maternal smoking are controlled for, growth of children around the world is quite similar.
The WHO is clear that these charts are not intended to apply just to breastfed babies. They can serve as an important early warning to doctors if a formula-fed baby is experiencing excessive weight gain - a particular concern because formula-fed babies are at risk for overweight and obesity. The WHO states, "Arguably, the current obesity epidemic in many developed countries would have been detectable earlier if a prescriptive international standard had been available 20 years ago."
With the CDC's endorsement, I think we can expect providers to finally start using these charts. And you can now discuss the use of these chart with your pediatrician with the backing of the CDC. This is a huge step forward.
Here are links to the WHO charts:
- Chart for girls, birth to two years, showing percentiles (pdf)
- Chart for boys, birth to two years, showing percentiles (pdf)
- A calculator for converting pounds to kilos, which you'll need to use the charts. Remember to first convert ounces to fractions of a pound - i.e. 6 lbs 8 oz = 6.5 lbs.
- Other charts, including height for age and body mass index for age
- Frequently asked questions about the new charts (particularly helpful if your pediatrician has questions)
- A video on the development of the new growth charts
- Software your pediatrician can use to implement the new charts