Medical Edge from Mayo Clinic

DEAR MAYO CLINIC:

Is it true that a child's future height can be predicted when they are 2 years old, based on their size at that time?

ANSWER:

A child's height at age 2 may be predictive of final adult height. But many factors can affect height. As they grow, children should be monitored regularly by a doctor to ensure they are growing properly and to detect any growth problems as soon as possible.

Doubling a child's height at age 2 can provide an estimate of how tall that child will be in adulthood. (Boys are usually a little taller than that number and girls a little shorter.) That's because by 2 most children have reached the growth chart percentile they will stay on as they grow. The percentile compares a child's height with that of other children the same age. For example, a child on the 50th percentile for height would be taller than half and shorter than half of other children his or her age.

After age 2, most healthy children grow steadily at about 2 inches per year until they reach puberty. During puberty they have a growth spurt, and shortly after that growth ends. Generally, most girls grow only about 2 inches more after they have their first menstrual period. Boys, by the time they need to start shaving and their voices deepen, have usually almost finished growing.

Genetics plays the biggest role in a person's final adult height. The best predictor of height is parents' height or, more specifically, midparental height. You can calculate midparental height by adding the mother's and father's height in inches. Add 5 more inches for boys or subtract 5 inches for girls. Divide by two. Most children will reach an adult height within 2 inches of mid-parental height.

Several factors can negatively affect final adult height. A chronic illness can considerably impede growth. Although some conditions -- such as hormonal disorders (thyroid disease, growth hormone deficiency) and genetic disorders (Down syndrome, Turner syndrome) -- are specifically linked to reduced adult height, any significant illness can decrease growth. Medications such as corticosteroids (e.g., prednisone or cortisone) can also reduce a child's growth and final adult height, especially if used in high doses for long periods.

Being underweight can impact final height, too, particularly during stages of rapid growth such as infancy and puberty. Eating disorders like anorexia nervosa often affect teenagers and can prevent the normal growth spurt that should occur during puberty. Unfortunately, once puberty is complete, the bony growth plates are closed, and there's no opportunity to get back the missed growth.

Keep in mind, though, that eating in excess will not help a child grow taller. Children who are obese are often taller when they're younger because obesity can affect the body's bone maturation, causing more rapid growth at a younger age. Heavier grade school children may be tall, but they often finish growing sooner than their peers. Eventually, those children have the adult height that would normally be expected in their family.

If a child is healthy, they should grow at a rate of about 2 inches per year, from age 2 until puberty. If your child isn't growing at that rate, see your pediatrician or family physician. Even healthy children should be seen by their doctors at least every two years to check that growth is normal. If a child is well into puberty and a treatable growth disorder is discovered, there may not be much that can be done to change final height. If discovered earlier, however, some excellent treatments are available.

Siobhan Pittock, M.D., Pediatric Endocrinology, Mayo Clinic, Rochester, Minn.

Medical Edge from Mayo Clinic is an educational resource and doesn't replace regular medical care.

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