Understanding Growth Charts: How Do Percentiles Work?

Children come in all different shapes and sizes! This is so clear when you look at school classroom pictures. All of the children are around the same age. However, some are incredibly tall, while others are smaller for their age.

It’s easy to compare your child to their peers, but all children grow at a pace that is best for them. By following children’s growth over time, their own unique pace can be identified. Some children grow steadily among the 20th percentile while others are within the 95th percentile for both height and weight!

What do growth charts measure?

At every check-up, you’ll notice that your child is always weighed, and measured for length as an infant and height as a child. An infant’s head circumference is also measured as an indicator of healthy brain development.

These measurements help you and your pediatrician ensure that your child is growing at a healthy rate.

The First 3 Years

During the first 36 months of your child’s life, they are growing at a very fast pace! This is obvious as you watch them reach all of those amazing milestones. Crawling, to walking, to running, and then reaching on top of the counter for the first time.

These little ones grow like a weed! Which is why there are two separate growth charts, one from birth to 36 months and one from 2 to 20 years.

Importance of Measuring Head Circumference

Measuring the distance around the head in small children helps pediatricians make sure the brain is developing normally. If the head circumference is too small or too large or development stops or increases in size too quickly, this may be a sign of a potential problem.

Reading the Charts

Step 1: Selecting the correct chart is important for correctly assessing their growth. For example, if you have a 14-month-old girl, it would be appropriate to select the CDC Growth Chart for Girls from Birth to 36 Months.

Step 2: First, find their age either at the top or bottom of the growth chart and draw a dark line from top to bottom.

Step 3: Next, locate your child’s weight in pounds on the far right side of the chart and draw a straight line from one side to the other.

Step 4: Finally, spot the location on the chart where these two lines cross. Find the curved line that is closest to this point and follow it to the right-hand side of the chart. This will tell you what percentile your little one is closest to.

Sometimes it is difficult to know where your child falls on the chart if the two lines cross at a point that doesn’t fall on one of the curved lines. If this is the case, find the line that is closest to this point, follow it to the right side of the chart, and you will have an estimate. Your child may fall between the 50th and 75th percentile for weight-for-age.

Understanding Percentiles

What is a Percentile?

A percentile is a measurement that is used to compare your child to their peers of the same gender and age. It is easy to think of a percentile as 100 children.

For example, if your child is 40th percentile for weight-for-age, your child weighs more than 40 of their peers (or 40%) and weighs less than 60 of their peers (or 60%).

Or if your child is in the 5th percentile for weight, that means that 95% of children of the same age and gender weight more than them.

Factors that Affect Percentiles

It’s important to realize that there are many factors that determine the size of your child and how they fall among the growth chart.

This includes genetics, physical activity level, nutrition, gender, environment, and even hormones! Especially as your children begin to go through puberty.

Healthy Ranges

Since every child is different in their own unique way, one percentile isn’t necessarily better than the others. As long as your child follows the curve over time, wherever that falls, they are growing appropriately.

For example, some children are much smaller than their peers. They would naturally fall in the 5th percentile for weight and height for their age. However, their entire family is very short in stature. For this child, the 5th percentile would be expected.

For other children, they may come from a family of very tall individuals contributing to their 95th percentile ranking. In this example, falling within the 95th percentile would not be a surprise.

Cause for Concern

Most concerns will typically develop from watching trends over time. If a child was following a specific percentile curve- trending nicely with the 30th percentile- and began to trend down quickly toward the 15th percentile, the doctor would take a closer look.

There might be a concern for inadequate nutrition or they are merely going through a growth spurt! Your pediatrician may want to investigate a bit.

If this happens, your pediatrician will work with you to help get your child back on track! If there is a concern for nutrition, consulting with a pediatric dietitian would be a great idea.

When in Doubt, Ask!

If you ever have any questions or concerns about changes in your child’s growth, don’t hesitate to speak with your pediatrician. They will provide reassurance and give excellent guidance on how to help your child stay on track.