Understanding Baby Growth Percentiles

How does your child measure up?

By Shelly Thacker Meinhardt

In this article:
Measuring Up
P is for Pattern
Highs and Lows
Leaps and Bounds
Head Room
Dreams of the Future

Do you leave your child's well-baby visits feeling confused by facts, figures, and growth charts? Baby growth percentiles are as varied and different as children themselves. Here is a primer to help you better understand what they mean for your child.

It's part of the normal routine of well-baby care: Your pediatrician measures your child's length, weight, and head circumference and notes them on a chart. You eagerly await the results, excited to hear that your bundle of joy is in the 90th percentile for height (Wow!), the 80th percentile for weight (Cool!), and the 75th percentile for head size (Ooh!). But what do these numbers really mean? Why are they important? Can they predict what your child will be like in the future?

If you're confused, you're not alone. Here's everything you need to know about baby growth percentiles: where they come from, what they reveal about your child's health, and when you should be concerned.

Measuring Up

Pediatricians in the United States began using government charts to measure babies' growth in 1977. The National Center for Health Statistics created the first set of charts to give doctors a simple tool they could use to monitor normal baby growth development, but the charts were based on a small study of formula-fed babies in one area of Ohio—and some of the statistics came from as early as 1929.

In 2000, the US Centers for Disease Control and Prevention (CDC) released new-and-improved baby growth percentile charts. These updated charts—currently used in most American pediatric offices—are based on a national survey of children from various regions and ethnic groups, and babies fed through breastfeeding as well as formula-fed babies are included.

P is for Pattern

When your doctor plots those dots on your baby's growth chart, she gets an instant snapshot of how your infant compares to other American babies of the same age. Separate charts are used for each gender, so your daughter will be compared to other baby girls and your son to other baby boys.

The "percentile" simply reveals where your baby growth ranks in comparison to the national survey. For example, if your daughter is in the 25th percentile for weight, that means she weighs more than 25 percent of baby girls her age, and less than 75 percent of baby girls her age.

There's no need to nibble your nails with worry about the percentile numbers you hear at any one office visit. "The important thing is the pattern over time," says Bradley S. Miller, MD, PhD, assistant professor of pediatric endocrinology at the University of Minnesota. "Looking at one point in time is not as helpful as looking at the comparison from one time to another."