What are growth charts?
Growth charts are tools that the doctor uses to evaluate and keep track of your child's physical growth. At each checkup, the doctor or nurse will measure your child's height and weight. Then she'll plot those numbers on a chart of national averages for children of the same age and sex.
In the end, she'll tell you what percentile your child is in. If the doctor tells you that your 3-year-old son is in the 75th percentile for weight, for example, that means 75 percent of the boys his age in the United States weigh the same or less than your child and 25 percent weigh more.
Beginning at age 2, the doctor will also keep track of your child's body mass index (BMI). This number — which expresses the relationship between your child's height and weight — helps the doctor decide if your preschooler is overweight, underweight, or at risk for becoming overweight.
The BMI chart is different for children than for adults, because a child's BMI should fluctuate as he grows. Preschoolers, for example, are generally leaner than babies and toddlers, so they typically have a lower BMI. Once a child reaches school age, though, the BMI number starts increasing, and it should continue to increase into adulthood.
Parents sometimes worry needlessly about their children's growth percentages. Remember that your child is an individual and will develop at his own pace. These measurements are only a general guide to help you and your doctor assess your child's growth.
What's important is that your child's growth curve, as it's plotted on the chart, is progressing. The doctor will be looking to see whether he's gaining appropriately each time (no big dips or spikes, for example).
The first set of growth charts covers from birth to 36 months. The second set is for children from 2 to 20, so there's some overlap.
On the left side of the height chart are centimeters; corresponding measurements in inches run along the right side of the chart. On the left side of the weight chart are kilograms; corresponding measurements in pounds run along the right side of the chart. All of these are included in the BMI chart. You can see the charts themselves on the Centers for Disease Control and Prevention Web site.