As easy as it is to make these comparisons and to draw conclusions about what you see, the reality is that kids grow at their own pace. Big, small, tall, short — there is a wide range of healthy shapes and sizes among children.
Genes and lifestyle factors like nutrition and physical activity play big roles in kids' growth and development. And those issues can vary widely from family to family.
So how does a doctor figure out whether a child's height and weight measurements are "normal"? Whether he or she is developing on track? Or whether there are any health problems that are affecting growth?
A doctor uses growth charts to help answer those questions. Here are some facts about growth charts and what they say about your child's health.
Are All Kids Measured on One Growth Chart?
No. Girls and boys are measured on different growth charts because they grow in different patterns and at different rates.
And one set of charts is used for babies, from birth to 36 months. Another set of charts is used for kids ages 2 to 20 years old. Also, special growth charts are used for children with certain conditions, such as Down syndrome.
Commonly used standard growth charts include:
Ages birth to 36 months (3
years):
Girls' length- and weight-for-age
Boys' length- and weight-for-age
Girls' head circumference-for-age
and weight-for-length
Boys' head circumference-for-age and
weight-for-length
Ages 2 to 20 years:
Girls' stature- and weight-for-age
Boys' stature- and weight-for-age
Girls ' weight-for-stature
Boys' weight-for-stature
What Measurements Are Put on Growth Charts?
Up until the time babies are 36 months old, doctors measure weight, length, and head circumference.
With older kids, doctors measure weight, height, and body mass index (BMI). It's important to look at and compare weight and height measurements to get a full picture of a child's growth.
Why Is Head Circumference Measured?
In babies, head circumference (the distance around the largest part of the head) can provide clues about brain development. If a baby's head is bigger or smaller than most other kids', or the head circumference stops increasing or increases quickly, it may indicate a problem.
For example, an unusually large head may be a sign of hydrocephalus, a buildup of fluid inside the brain. A head that's smaller than average may be a sign that the brain is not developing properly or has stopped growing.
What Are Percentiles?
Percentiles are measurements that show where a child is compared with others. On the growth charts, the percentiles are shown as lines drawn in curved patterns. When doctors plot a child's weight and height on the chart, they see which percentile line those measurements land on. The higher the percentile number, the bigger a child is compared with other kids of the same age and gender, whether it's for height or weight; the lower the percentile number, the smaller the child is. For example, if a 4-year-old boy's weight is in the 10th percentile, that means that 10% of boys that age weigh less than he does and 90% of 4-year-old boys weigh more.
How Are Percentiles Determined?
The Centers for Disease Control and Prevention (CDC) created the growth charts that are most commonly used in the United States. They were last updated in 2000. After collecting growth measurements from thousands of U.S. children over a period of time, the CDC was able to show the range of these measurements on one chart, using percentile curves.
Being in a high or a low percentile does not necessarily mean that a child is healthier or has a growth or weight problem. Let's say that 4-year-old boy, who is in the 10th percentile for weight, is also in the 10th percentile for height. So 10% of kids are shorter and weigh less than he does, and most kids — 90% — are taller and weigh more. That just means that he's smaller than average, which usually doesn't mean there is a problem. If his parents and siblings are also smaller than average, and there are other signs that he's healthy and developing well, doctors would likely conclude that there's no cause for concern.
If you have any questions about your child's growth — or growth charts — talk with your doctor.
