# How Do Doctors Predict a Child's Height?

by Sharon Perkins

If you're tired of hearing your mom predict that your son will top 6 feet when you feel certain that his genetic lottery holds no tall genes, you might wonder what tricks doctors use to predict a little person's height. Doctors have no magical powers (you might suspect this already) or crystal balls to help them make these predictions; what they do have is knowledge of several fairly accurate formulas to determine adult height. You can use these to convince your mom that pro basketball probably isn't in your son's future.

## Genetic Factors

Several genes control height, making the final results somewhat unpredictable. But genetics aren't the only factor; nutrition and environment also play a part in the heights your kiddos will reach. Height is around 60 to 80 percent genetic and 20 to 40 percent environment, according to Chao-Qiang Lai, molecular biologist at the Jean Mayer U.S. Department of Agriculture Human Nutrition Research Center on Aging at Tufts University. If a number of tall genes make it into your kid's genetic code, he could be taller than either parent. If you grew up severely undernourished, you probably didn't reach your full height potential and your kids could also look down on you as adults.

## Averaging Parent's Heights

One way of figuring how tall your kids will be is to use your and your partner's height as a basis. Add the two together, in inches, then add 5 inches for a boy or subtract 5 inches for a girl. Divide the total by two to get a rough estimate of how tall your kids will be. Because this is only an average, some of your kids will be taller and some shorter, but it gives you a starting place for determining height. Most kids will fall within 2 inches of this estimate, according to pediatric endocrinologist Dr. Siobhan Pittoc of the Mayo Clinic.

## Doubling at Two

A simpler method of predicting height involves taking your kid's height at age 2 and doubling it. That's it -- the entire method in one easy math problem. Girls might be a little shorter and boys a little taller, notes Dr. Pittoc. This method assumes that your toddler or preschooler will continue to plot -- not plod -- along the same growth track from age 2 onward, barring any severe illnesses or health changes. So a 2-year-old who falls along the 50th percentile for height will probably remain within the same percentile as an adult.

## Factors That Affect the Results

Several factors can skew the results of these height predictors. Obese kids, for example, tend to be taller at a younger age, because obesity affects bone maturation. Some medications, such as steroids can cause slower physical growth and can reduce height permanently. Eating disorders and hormonal disorders can also have a negative impact on height. Most kids grow around 2 inches per year from age 2 up until puberty, according to Dr. Pittoc. At puberty, boys will add an additional 11 inches and girls around 10 inches, family practitioner and author of "The Growth Spurt: Calculating Your Child's final Adult Height" Dr. John Alevizo reports.