You just learned that your baby is in the 90^th percentile for height. Does this mean she will be really tall when she grows up?

Each time you take your baby to the pediatrician, you hear numbers related to how she is growing. But where do the numbers come from and what do they mean?

At each well visit, your pediatrician will measure your baby's weight, length and head circumference (this measurement is usually taken until age 2). The results are plotted on a standardized growth chart according to your baby’s age and gender.

The Centers for Disease Control and Prevention (CDC) recommends using World Health Organization (WHO) growth charts for children from birth to age 2. After age 2, pediatricians typically use the CDC's growth chart, which includes weight, height and body mass index (BMI) through age 20. The American Academy of Pediatrics provides growth charts you can download.

The growth chart is based on national data of children from various regions and ethnic groups. Your pediatrician will determine percentiles for your child’s height, weight and head circumference. The percentiles show you how your baby is growing compared to other babies the same age and gender.

As your child grows, your pediatrician will plot these measurements on the growth chart to indicate whether she is following a curve, which indicates a pattern of healthy growth.

The higher the percentile, the taller or bigger your baby is compared to other babies her same age. For example, a girl in the 75th percentile for weight is larger than 75 girls out of 100, and smaller than 25 girls out of 100. Lower percentages represent a smaller or shorter than average child.

Your child’s growth is influenced by everything from genetics, to environment, to nutrition, to activity, to health problems. In a healthy, well-nourished child, these measurements will increase at a predictable rate, creating a curve along the growth chart.

Try not to get too hung up on the numbers though. A healthy child can fall anywhere on the chart. A lower or higher percentile doesn't mean there is something wrong with your baby. Regardless of whether your child is in the 95^th or 15^th percentile, what matters is that she or he is growing at a consistent rate over time.

When should I worry about my baby's growth?

Your baby’s growth should be following a consistent curve. If your child’s growth pattern suddenly changes, your doctor will want to figure out why. This can help your doctor find and address any nutritional, developmental or medical issues. A dramatic change, such as a drop from the 50th percentile to the 5th, for instance, would be a red flag.

Also, your child’s height and weight percentiles should be in roughly the same proportion. If your daughter is in the 10th percentile for weight and the 90th percentile for height, your pediatrician might monitor her nutritional intake more closely. If your baby’s weight keeps pace with her height, chances are she’s perfectly fine.

Genetics play a big role in how your baby grows, and what’s normal for your child depends on what’s normal for your family. For instance, if both parents are relatively short, it makes sense if your child is on the shorter side.

Percentiles are just one of many tools your pediatrician uses to monitor your child’s health. Each child is unique. As long as your little one is following her own unique pattern, chances are she’s growing just fine.

If you have any questions about how your baby is growing, talk to your child’s pediatrician.

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