What are growth charts?
Growth charts are commonly used tools for tracking a child’s physical growth. By charting a child’s height, weight, and head circumference over time, pediatricians and parents can see if a child is growing at a rate that’s typical for their age. The two most popular growth charts used are the Centers for Disease Control and Prevention (CDC) and the WHO growth charts.
The CDC growth charts are based on data obtained from a cross-section of U.S. children who were formula-fed. The WHO growth charts for children up to 5 years are more internationally applicable as they are based on the Multicenter Growth Reference Study- a community-based, multi-country project which included children who were breastfed and were raised in environments that encouraged optimal growth of children (i.e. non-smoking parents).
These two charts differ slightly particularly in the first 2 years of life as breastfed babies typically have faster weight gain during the first three months of life compared to formula-fed infants. Usually, the WHO charts are used for children from birth to two years of age and the CDC charts for older children (American Academy of Pediatrics recommendations).
What do the curves mean?
Growth charts can be confusing to read. They consist of a series of curves called percentiles which are marked with numbers. Percentiles are measurements that show where a child is compared with other kids. For example, if a boy’s weight is at the 25th percentile, it means that 25 % of boys that age weigh less than he does and 75% of boys that age weigh more.
The uppermost, middle and lowermost percentile curves are in bold and as long as the child measurements are between the uppermost and lowermost bold lines, the child is doing fine. Percentiles are not like test scores. Being in a high or a low percentile doesn’t necessarily mean that a child is healthier or that there is a growth/ weight problem. In fact, being in a higher weight percentile may even indicate obesity! Rather than a single measurement, it is more important to plot several measurements and assess the trend of your child’s growth over time.
Growth charts for children from birth to 2 years of age:
Boys:
Weight for length (to assess obesity) and the Head circumference-for-age (for head growth)
Girls:
Weight for length (to assess obesity) and the Head circumference-for-age (for head growth)
Growth charts for children from 2 to 20 years of age:
Boys:
BMI-for-age (to assess obesity)
Girls:
BMI-for-age (to assess obesity)
*Note: Length is used for children less than 2 years as it is measured while lying down. Height is used after 2 years of age and is measured standing up.
How to read the charts?
Step 1: Find the child’s age at the bottom of the chart and draw a line upwards
Step 2: To check the weight, look at the lower set of curves in the weight and lenght/height charts and find the child’s weight on either the right or left-hand side of the chart. Draw a line horizontally from there.
Step 3: Find the spot where these two lines intersect or cross each other and mark it with a dot
Step 4: Find the curve that is closest to this spot and follow it up to find the number on it…that is your child’s percentile.
Step 5. Repeat the same for height using the upper set of curves in the same charts