MONDAY, Sept. 28, 2009 (HealthDay News) -- Parents want to know how their children measure up on the growth charts widely used in pediatrician's offices, but many parents don't understand how to read or interpret the information, a new survey shows.
About 85 percent of parents could look at a growth chart with one point plotted and correctly identify that the point corresponded to the child's age, according to an online survey of a nationally representative group of 1,000 moms and dads. About two-thirds of parents were able to identify both a child's weight and percentile on a chart with one plotted point.
But only 56 percent could correctly identify the meaning of "percentile" from a list of choices. In the context of a growth chart, a percentile measures how a child stacks up to his or her peers. A child who is in the 80th percentile for height, for example, is taller than 80 percent of other children his or her age, while a child in the 25th percentile, is shorter than 75 percent of his or her peers.
Only one-third of parents could identify a child's age, weight and percentile on a chart, as well as the correct definition of percentile, according to the study in the October issue of Pediatrics.
Growth charts were developed in the 1960s to help physicians monitor a child's development, said study author Dr. Elana Pearl Ben-Joseph, consulting medical editor at Nemours Center for Children's Health Media. The latest versions, from the U.S. Centers for Disease Control and Prevention, were updated in 2001.
While the charts were meant for use by health-care providers, in practice, physicians often use the charts as visual aids for parents. About 31 percent of parents said they marked their child's growth on a chart at home.
"Growth charts can be helpful if used properly and if the parents understand them and they are explained properly," Ben-Joseph said. "But they can be detrimental if not explained well or if parents aren't understanding them."
And many don't. In the survey, about half of parents said a child in the 10th percentile for height and weight was underweight. To doctors, the child's height and weight is proportional and probably no cause for concern, Ben-Joseph noted.
Many parents expressed concern about a child in the 25th percentile for height and weight year after year. About 16 percent said they would encourage the child to eat more and 18 percent said they didn't know what the information meant.
A child following a 25th percentile growth curve is smaller and lighter than average, but again, nothing to worry about, Ben-Joseph explained.
When reading growth charts, doctors tend to look for abrupt changes, such as a child whose height or weight trend suddenly drops off, which could be a sign of a problem. They also look for proportionality in height and weight.
A child with a height in the 10th percentile and weight in the 90th percentile is overweight, though about half of parents in a survey didn't realize this.
The confusion over growth charts brings up the larger issue of "numeracy" -- the numerical counterpart to literacy -- or the ability of patients to understand risk, statistics, graphs and charts used with increasing frequency in health care, said Dr. Goutham Rao, clinical director of the Weight Management and Wellness Center at Children's Hospital of Pittsburgh.
"When a patient comes to a doctor's office or a health-care facility, there are specific numeracy skills they need to understand their condition and what transpires in the health-care environment," Rao said. "It's not just patients that can have trouble with this: physicians can also have difficulty putting numbers into terms patients can understand."
Even so, growth charts remain a useful tool for broaching the delicate issue of a child's weight with parents, Rao pointed out. About 12.4 percent of children 2 to 5 years old are overweight, 17 percent of children aged 6 to 11 are overweight and 17.6 percent of teens aged 12 to 19 are overweight, according to the U.S. Centers for Disease Control and Prevention.
"Many times parents don't recognize that their child is overweight," said Rao, whose clinic uses electronic charts so parents can take home printouts of the result. "We can show the parent where the child is on the growth chart, provide a very detailed explanation of the numbers and make sure the parents are able to understand it. Then we can ask the parents if it's something they would like to work on."
Further research should be done into developing growth charts that are easier for parents to understand, Ben-Joseph added.
"There is a desire by the parents to see the growth chart and have doctors talk to them about it," Ben-Joseph said. "It's important for doctors to be aware that not all parents will understand these complicated mathematical concepts and to take that into account when they are doing the explaining."
The Nemours Foundation has more on growth charts.