Growth charts are used to compare your child's height, weight, and head size against children of the same age.

Growth charts can help both you and your health care provider follow your child as they grow. These charts may provide an early warning that your child has a medical problem.

Growth charts were developed from information gained by measuring and weighing thousands of children. From these numbers, the national average weight and height for each age and gender were established.

The lines or curves on growth charts tell how many other children in the United States weigh a certain amount at a certain age. For example, the weight on the 50th percentile line means that one half of the children in the United States weigh more than that number and one half of the children weigh less.

WHAT GROWTH CHARTS MEASURE

Your child's provider will measure the following during each well-child visit:

• Weight (measured in ounces and pounds, or grams and kilograms)
• Height (measured while lying down in children under age 3, and while standing up in children over age 3 and older)
• Head circumference, a measurement of the head size taken by wrapping a measuring tape around the back of the head above the eyebrows

Beginning at age 2, a child's body mass index (BMI) can be calculated. Height and weight are used to figure out the BMI. A BMI measurement can estimate a child's body fat.

Each of your child's measurements is placed on the growth chart. These measurements are then compared with the standard (normal) range for children of the same sex and age. The same chart will be used as your child grows older.

HOW TO UNDERSTAND A GROWTH CHART

Many parents worry if they learn that their child's height, weight, or head size is smaller than those of most other children the same age. They worry about whether their child will do well in school, or be able to keep up in sports.

Learning a few important facts can make it easier for parents to understand what different measurements mean:

• Mistakes in measurement can happen, for example if the baby squirms on the scale.
• One measurement may not represent the big picture. For example, a toddler may lose weight after a bout of diarrhea, but will likely regain the weight after the illness is gone.
• There is a wide range for what is considered "normal." Just because your child is in the 15th percentile for weight (meaning 85 out of 100 children weigh more), this number rarely means your child is sick, you are not feeding your child enough, or your breast milk is not enough for your baby.
• Your child's measurements do not predict whether they will be tall, short, fat, or skinny as an adult.

Some changes to your child's growth chart may worry your provider more than others:

• When one of your child's measurements stays below the 10th percentile or above the 90th percentile for their age.
• If the head is growing too slowly or too quickly when measured over time.
• When your child's measurement does not stay close to one line on the graph. For example, a provider may worry if a 6-month-old was in the 75th percentile, but then moved to the 25th percentile at 9 months, and dropped even lower at 12 months.

Abnormal growth on the growth charts is only a sign of a possible problem. Your provider will determine whether it is an actual medical problem, or whether your child's growth just needs to be watched carefully.