What to Know About Infant Growth Charts

Every baby grows at their own pace. Given the wide range of "normal" when it comes to a baby's size and growth, it's hard to know how your child measures up to standards. That's why pediatricians track physical development like length, weight, and head circumference with baby growth charts.

What Is a Baby Growth Chart?

Genetics plays a major role in a baby's physical development—as do factors like environment, nutrition, activity level, and health condition. Even breastfed babies have different weight and height standards than their formula-fed counterparts. According to the Centers for Disease Control and Prevention (CDC), breastfed babies tend to gain weight slower than formula-fed babies during the first 12 months of life.

Thanks to these trends, many parents wonder what a "normal" baby should look like, and they worry if their little one is bigger or smaller than other infants their age. To address these questions, the medical community has created growth charts that help pediatricians and parents identify whether a child is growing at a healthy rate by tracking the baby's height, length, and head circumference from birth to 24 months and beyond.

In 1977, the National Center for Health Statistics (NCHS) created the first growth chart. Since then, the CDC and The World Health Organization (WHO) have each created growth charts. Growth charts can feel intimidating to some parents, but it is important to remember that a growth chart is one of many tools your doctor uses to help assess how your child is growing and developing.

What Do Infant Growth Charts Measure?

Most infant growth charts track measurements for length/height, weight, and head circumference. Pediatricians take these measurements during your baby's regular wellness exams. Plotting the information on a growth chart can help them identify patterns.

Growth charts also compare your baby's measurements to those of other babies of the same age. It is important to note that separate growth charts exist for males and females and children with specific developmental conditions such as Down Syndrome or premature birth.

Here is what your doctor will measure.

Length

Using a tape measure, a doctor determines the distance from your baby's head to their feet—usually while they're stretched on an exam table. Some parents may wonder if the length measurements on a growth chart can help predict future height; they don't. The length measurement is meant to help identify if your baby is growing at an expected rate for their age.

Weight

A baby scale provides the most accurate weight measurements. If your baby is under 12 months, you'll probably need to take off their clothes and ensure they are in a fresh diaper before laying them on the scale. Typically, children whose weight falls between the 5th and 85th percentile are considered healthy. Some kids may fall below 5% or above 85%, which is not necessarily an indicator of poor health but is something that a doctor would want to monitor.

Head circumference

Also taken with a tape measure, head circumference clues you into your baby's brain development. For example, a significantly larger-than-average head may signal a condition called hydrocephalus, characterized by excess fluid on the brain. On the other hand, if the distance around the head seems small for their age and overall size, the baby may have developmental delays.

In a study published in Nature, researchers found that atypical head circumference growth in male infants was a reliable predictor for neurodevelopmental disorders. While more studies need to be done, the results demonstrate the importance of how growth charts can cue doctors into potential health issues.

How to Read Baby Growth Charts

Growth charts can be hard to decipher at first glance. Here's how to read WHO and CDC baby growth charts for length and weight, which are linked at the bottom of the article:

1. Locate your child's length or weight (depending on what you're measuring) on the grid's left- or right-hand side, also called the Y-axis.
2. Find your baby's age in months at the top of the graph, also called the X-axis.
3. Follow the lines until they intersect. They should cross somewhere along the curves, which represent percentiles.
4. Follow the curve to see the percentiles on the right-hand side of the graph. The percentile lines show your baby's measurements compared with other babies' measurements.

Generally speaking, higher percentiles mean your kid has bigger measurements than average—and vice versa for smaller percentiles. For example, if the curved line is "75" when measuring length, then your baby is in the 75th percentile for length. This means that 75% of babies their age are shorter than your child, and 25% are taller than your child.

How to Interpret the Data

Instead of analyzing the actual measurements, doctors pay attention to patterns and consistencies on the growth charts. A constantly growing, proportionate baby doesn't raise any red flags, but a noticeable change in percentiles, for example, should be closely examined.

For instance, a baby having a lower weight and shorter length for their age isn't usually worrisome; it might mean your baby has a genetic predisposition to being short and thin. But going from a high-weight percentile (like 80th) one visit to a low-weight percentile (like 25th) the next might indicate a health issue like not eating enough. On the other hand, gaining lots of weight for your baby's age could mean that they are eating too much, which could lead to future health and weight problems.

Remember that all babies grow at different paces. Measuring at the 50th percentile isn't better or worse than the 15th, 70th, or 99th percentile. As long as your baby is experiencing consistent growth patterns, they will likely grow up happy and healthy.

The Difference Between WHO and CDC Growth Charts

It is important to understand that the growth charts used by the WHO and the CDC differ. The WHO growth chart describes measurement standards of healthy children worldwide.

The CDC growth chart, on the other hand, describes American children based on the growth data of kids living in the U.S. since 1977. The CDC updated its growth chart in 2000 to include considerations such as racial and ethnic backgrounds and a new age-based body mass index (BMI) that screens for childhood obesity. The updated growth chart also considers the differences in weight growth between breastfed and formula-fed babies.

The CDC recommends that pediatricians and parents use the WHO growth charts for babies under 24 months and the CDC growth chart for children 2 years and up.

WHO growth charts

• Boys Chart
• Girls Chart
• Boys Chart with Head Circumference
• Girls Chart with Head Circumference

CDC growth charts

• Boys Chart
• Girls Chart
• Weight Data Table for Boys and Girls
• Length Data Table for Boys and Girls