It's tricky to predict a child's adult height

03/31/2014 5:49 PM

03/31/2014 5:54 PM

Q. Is it true that a child’s predicted adult height is twice his height at age 2?

A. Several factors determine final adult height, including genetics, gender, health and nutrition. At each checkup, a child’s measurements are plotted on a growth chart to determine his height and weight percentiles. After the first year of life, most children will develop a predictable growth pattern: If a boy is 50th percentile for height at ages 4, 5 and 6, he will most likely be average height as an adult – but this is not always the case.

Children will continue growing until the growth plates in their bones fuse, which occurs at different ages for different children. This is the reason that some teens will stop growing at age 13 while others are still growing at age 17. Growth plate measurements can be used to determine a child’s bone age. Children who are overweight or have early-onset puberty will typically have an advanced bone age and reach adult size at a younger age. There are other conditions that may delay a child’s bone age, making height prediction based solely on growth charts less reliable.

Another method commonly used to calculate predicted adult height based on genetics is something called a mid-parental height. This calculation is as follows:

• (Mother’s height in inches + Father’s height in inches) divided by 2

• Add 2.5 inches for boys; subtract 2.5 inches for girls

• The mid-parental height range is this number, plus or minus 2 inches.

The strategy of doubling a child’s height at age 2 years for predicting his or her final height has not been proven to be accurate. In fact, the average girl is 34 inches tall at age 2. Twice this number is 5 feet 8 inches, but the average adult height for a girl is 5 feet 4 inches.

In summary, it is important to monitor your child’s growth and development at regularly scheduled checkups; however, predicting a final height at a young age is difficult.

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