Growth charts grow up

It’s part of the routine during every well-baby visit. Your baby is weighed and measured, and those numbers are entered onto a growth chart that is part of your baby’s file.

What does it all mean? Do you feel a little anxious if your baby isn’t following “the curve” or just a little bit proud if he tops the 90th percentile? And what does it mean that the old charts are being replaced with new ones?

The curves or lines on growth charts are used to compare an individual baby’s growth against the growth patterns of a large number of babies. If your baby is at the 50th percentile, for example, that means that about half the babies his age are larger, and half smaller. By plotting the baby’s weight and height over several months, a pattern emerges. You can see if the baby is growing at a rate similar to the larger group, or growing more, or less, quickly. For example, a baby who is at the 75th percentile for a couple of visits, but then drops to the 25th percentile at the following visit, and a month later to the 10th percentile, may have a health problem of some kind, even though he is continuing to gain weight.

Why new charts?

For many breastfeeding mothers, though, having their babies’ growth charted sometimes led to worries: Often the baby seemed to gain well for the first few months, but then began to drop to lower percentiles. Did this mean a problem with milk production? Was it time to supplement with formula?

Some experts, seeing this pattern frequently repeated, began to suspect that maybe the problem was with the charts and not the babies. The current growth charts usually used in Canada are from the US Centers for Disease Control and Prevention (CDC), and are based on observations of infants across the US. The breastfeeding rate in the US is lower than in Canada, and fewer than 50 percent of the infants whose growth was followed to create the charts were even partially breastfed for more than three months.

The Canadian Paediatric Society (CPS) notes that this may have created a problem: “Because growth rates may differ, misinterpretation of the growth rate of an exclusively breastfed infant plotted on charts that include formula-fed infants might lead to inappropriate counselling to discontinue breastfeeding.”

The World Health Organization (WHO) decided to tackle this problem by developing new charts that would be based on babies who were fed according to current recommendations: exclusive breastfeeding for six months, followed by the introduction of appropriate complementary foods and continued breastfeeding for two years and beyond. They chose six sites around the world where children were monitored; none were in Canada, but one was in California, under the supervision of University of California professor of community nutrition Kathryn Dewey.

WHO scientist Randa Saadeh, who worked on developing the new charts, explains: “Other growth charts were developed without considering the feeding of the baby or included a population that had a strong tendency to overweight or obesity.” The new charts are described as standards because they indicate how babies should grow when they are fed according to recommendations known to promote healthy growth and development.

What’s different?

Saadeh comments that the babies from around the world showed remarkably consistent growth patterns that were somewhat different from those represented on the older charts. The new charts show more rapid growth in the first two or three months, followed by slower growth for the rest of the first year. How do the two charts compare? Here’s an example: At one year, a baby weighing nine kilograms would be right at the 50th percentile on the WHO chart, but only at the 25th percentile on the old CDC chart.

“These standards are definitely better for assessing the growth of breastfed infants,” says Dewey. But she adds that there is another important benefit: “It’s more likely that overweight infants will be identified. This shouldn’t trigger efforts to put infants on a diet, but parents can then talk to their health care providers about healthy feeding practices such as avoiding sugary drinks and foods.”

Saadeh agrees that this increased ability to identify infants at risk of later obesity is an important benefit of the new standards. It is important to monitor not only the weight but also the height, since a child could be big but not overweight.

Saadeh feels these standards will be very helpful for breastfed babies. “Breastfeeding mothers usually find their babies’ growth follows one of the lines on the chart with very little deviation,” she says. This was not always the case when charts included a high proportion of formula-fed babies, and Saadeh hopes this will lead to fewer recommendations for supplementation of breastfeeding or even weaning.

How to find the charts?

Can you expect to see the WHO standards in your doctor’s office soon? Dewey says that, in the United States, the American Academy of Pediatrics has approved the use of the charts for children up to two years old. Saadeh adds that the standards are in use or under review in many countries around the world.

In Canada, an expert advisory group with representatives from the Dietitians of Canada, the CPS, The College of Family Physicians of Canada and the Community Health Nurses Association of Canada has been created to consider these standards. They anticipate releasing a statement in spring 2008.

Meanwhile, some individual physicians have started using the charts. Parents can also download them from the WHO website who.int to make their own comparisons.

For help in understanding how to use the charts (and to find a booklet you can download to chart your child’s growth over the years) visit the WHO Child Growth Standards.