Charting Your Child's Growth

Your child's doctor has probably told you regularly, probably at each of your child's routine checkups, that your child is in a specific percentile for height and for weight. Like many parents, you probably nodded your head and maybe made a note for your child's baby book or health records. Otherwise, you had no clue exactly what those numbers meant. Or maybe you assumed that a high score meant your child was growing well. Here's your chance to learn what those numbers really mean.

Types of Charts

Your child regularly gets her height and weight measured at the pediatrician's office (and head circumference, at thirty-six months and younger). The doctor plots that information on a graph. The results show your child's growth trends from birth on as well as size in comparison to other children of the same age.

Your doctor has several other national growth charts against which to compare your child, including weight for stature (or height), weight for length, weight for age, stature for age, BMI for age, and head circumference for age (used for charting brain development and detecting potential developmental problems in infants and toddlers). The charts your provider uses will depend upon your child's age and the standard at your doctor's practice.

The 2000 CDC growth charts are based on survey information compiled from 1963 through 1994. The data has been adjusted to account for the increase in American overweight children and adolescents that began in the 1980s. Therefore, the percentiles do not actually reflect exact population references; for instance, more than 5 percent of today's American children are considered overweight. Still, they are intended to be used as this type of reference guide.

The growth charts that your child's pediatrician uses were developed in 1977 by the U.S. Centers for Disease Control (CDC), using data collected from the National Health Examination Survey (NHES) and the National Health and Nutrition Examination Survey (NHANES). The CDC updated these charts in 2000 to incorporate new data, including revised national statistics for infants and new charts showing the relationship between body mass index and age.

Percentiles

Your child's measurements, as related to those of other children the same age, are expressed in terms of a percentile. Standard CDC growth charts include growth curves from the 5th to the 95th percentile. A set of charts is also available that range from the 3rd to the 97th percentile for use with children who fall above or below the standard charts in weight and/or height. If your son is in the 95th percentile for his weight, it means that he weighs more that ninety-five percent of the statistical sampling of U.S. boys his age. It also means that he weighs less than 5 percent of the boys surveyed. That number by itself doesn't always mean a lot, but when you factor in his body mass index (BMI), which takes his height into account as well, you get a more complete picture.

Body Mass Index

The American Academy of Pediatrics (AAP) recommends that the body mass index (BMI) of children and adolescents be calculated and plotted annually to assess growth patterns. For children and young adults between the ages of two and twenty, the CDC introduced a BMI-for-age chart in 2000. A weight-for-stature chart for the same age group is also available, but the CDC recommends that the former be used because it is more effective as a screening tool.

The growth charts used by your child's pediatrician were developed by the National Center for Health Statistics (NCHS) in 1977 using data collected from the National Health and Nutrition Examination Survey (NHANES). In 2000, the CDC updated the charts to incorporate new data, including revised national statistics for infants and new BMI-for-age charts.

Body mass index is a measurement of your child's body weight adjusted for height. It can help your child's doctor screen for weight problems, although it isn't diagnostic in and of itself. This means that further assessment will be required if the BMI indicates your child may have a weight problem. Keep in mind that BMI-for-age charts are not used for children under age two. Studies have found that a high BMI in this age group is not directly associated with either weight-related medical problems or a risk of obesity in adulthood.

To get an accurate BMI reading, your child's physician will first measure height and weight. This information is then plotted on the appropriate CDC height-for-age and weight-for-age growth charts. Once these measurements are taken, BMI can be computed using the following mathematical formula:

BMI = Weight (lb) / Stature (in) / Stature (in) × 703

Note: Stature is equivalent to standing height.

Or, in metric measurements:

BMI = Weight (kg) / Stature (cm) / Stature (cm) × 10,000

Measuring Up

Once your child's BMI is computed, the pediatrician can plot it on the BMI-for-age chart to figure out the BMI percentile — that is, where your child's BMI falls in comparison with other children of the same age. Table 3-1 shows the percentile indicators for underweight, risk of being overweight, and overweight. Weight-for-length and weight-for-stature indicators are also included for children assessed with those charts.

Table 3-1: Weight Indicators

Underweight

Risk of Overweight

Overweight

BMI-for-Age Percentile

Below the

From the 85th to

95th percentile

5th percentile

the 94th percentiles

or greater

Weight-for-Length/Stature Percentile

5th

N/A

95th

Note:Unlike guidelines for adult overweight and obesity, overweight indicators for children are based on percentiles rather than on specific BMI cutoffs. Children are still growing and developing, so it's important to evaluate their size in relationship to their peers rather than the static guidelines used in adulthood.

If your child is between the ages of two and five, your provider may use a weight-for-stature chart to plot growth rather than a BMI-forage chart. The CDC offers these growth charts as a tool for pediatric care providers who are still making the shift to the BMI standard.

Is It Fat or Something Else?

If your child's BMI-for-age falls into a percentile that categorizes him as overweight or places him at risk of becoming overweight, your doctor will need to do some further assessment. It is necessary to determine whether the issue is one of weight or whether there's another underlying problem. Again, BMI is only a screening tool — it's a measure that can't diagnose a weight problem by itself. A child who is involved in athletic activities that build significant muscle mass, such as weight-lifting, may have a high BMI that isn't attributable to excess fat. In addition, children whose parents have large musculoskeletal frames (tall and broad physiques) may have a higher BMI without being overweight.

To determine whether a weight problem is a possibility, your child's doctor should perform additional assessments, including these:

  • Family history — Your doctor will ask if there is anything in your family background or medical history to indicate a propensity towards weight problems or weight-related complications, such as Type 2 diabetes and heart disease.

  • Physical examination — Your child may undergo testing for potential weight-related complications, including cholesterol screening, blood pressure, and blood glucose testing.

  • Skin-fold measurements — A measurement of skin-fold thickness on the back of the triceps (on the upper arm) of 95 percent or higher is usually considered an indicator of a weight problem.

  • Activity and nutritional assessment — Your child's doctor may interview you and your child about nutritional intake and exercise habits to determine if there is an imbalance in either that could be causing weight gain.

From birth up to age three, your child's growth is plotted on a length-for-age and weight-for-length chart. At these ages, a child's height is measured in a recumbent (lying down) rather than a standing position. Two-year-olds can be plotted on either a weight-for-length or a weight-for-height chart.

  1. Home
  2. Overweight Children
  3. Acceptance and Action: Identifying the Problem
  4. Charting Your Child's Growth
Visit other About.com sites: