Grow, Baby, Grow! from http://www.babyzone.com/baby/baby-health-and-safety/baby-growth-percentiles_71897

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.

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.

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.\"

According to the American Academy of Pediatrics, in a healthy, well-nourished baby, the height, weight, and head-size measurements will increase at a predictable rate, creating a curve along the growth chart. Each child is unique, so your pediatrician expects your baby to follow her own unique curve. How she compares to other babies isn\'t nearly as important as, \"Is she still following her own established pattern?\"

Even if your baby falls at the extreme high or low end of the chart, there\'s usually no cause for alarm. \"A healthy child can fall anywhere on the chart—even above the 97th percentile or below the 3rd percentile. They\'re just at the edges of the norm,\" Dr. Miller says.

What\'s important is that the height and weight percentiles should fall in roughly the same neighborhood. If your daughter is in the 10th percentile for weight and the 25th percentile for height, everything\'s probably fine and she just happens to be petite. However, if she\'s in the 10th percentile for weight and the 90th percentile for height, your doctor might become concerned and monitor her nutritional intake more closely.

Keep in mind that, while nutrition is important, genetics plays a huge role in how your baby grows. According to Dr. Miller, a child will usually mirror the growth pattern of the same-sex parent. That means if you were tall and thin at 18 months, your daughter probably will be, too. And if you\'re concerned that your toddler son is on the short side, ask your mother-in-law to dig out your husband\'s baby photos. Chances are, he looked the same at that age. Like mother, like daughter. Like father, like son.