Gazing into your newborn's eyes, it’s tough to imagine that tiny face (and those teensy hands and feet) will one day be about as big as yours.
And while it’s impossible to know what your baby will look like when she grows up, there is one thing you might be able to predict while she’s still relatively little: her future height.
Factors that affect your child's future height
A number of factors are at play in determining your child's height as an adult, including:
Genetics
As you might guess, heredity has a lot to do with how tall your baby will be, accounting for about 80 percent of your baby's height. If you and your mate are tall, chances are you’ve got a kid who’ll one day need extra-long pants too.
Sex
The average American man is 5.5 inches taller than the average American woman, according to the Centers for Disease Control and Prevention (CDC).
Exposure to smoke
Smoking cigarettes during pregnancy has been shown to reduce the height of an expecting woman's baby.
Nutrition
Having not enough to eat or eating very poorly — especially within the first 1,000 days of life, according to the American Academy of Pediatrics (AAP) — can make kids deficient in the vitamins and nutrients they need to grow. And that can permanently stunt a child’s growth and decrease adult height.
Exercise
Most kids don’t get nearly enough exercise — but a child who participates in extremely intense exercise at a young age can have a slowed or changed growth pattern.
Medical conditions
A number of very rare conditions can also affect a child’s adult height, including:
- Turner syndrome, a chromosomal disorder that results in short height and is usually apparent by about age 5.
- Gigantism, a disorder where an excess of growth hormone during childhood causes kids to be larger than other children their age.
- Dwarfism, where kids grow to an adult height that’s under 4 feet due to genetic disorders or other medical conditions. The most common type of dwarfism, achondroplasia, accounts for 70 percent of all cases and is detected either in utero or shortly after birth.
- Childhood growth hormone deficiency, a disorder where the pituitary gland does not make enough growth hormone, resulting in slow or flat rate of growth. While it’s sometimes noticed at birth, it may not be diagnosed until a child is 2 or 3 years old.
- Chronic childhood illnesses like severe arthritis, untreated celiac disease or cancer may slow a child's growth.
- Chronic use of some medications, especially corticosteroids, can impede a child's growth.
How to figure out how tall your child will be
While no test is 100 percent accurate, once your child is 2 years old, his doctor can begin to predict his adult height using the following methods:
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X-rays
Also known as the Bayley-Pinneau scaling law, a doctor uses an X-ray of a child’s hand and wrist to determine skeletal age (also called bone age). By comparing this information to historical data, doctors can make fairly accurate predictions of adult height.
Khamis-Roche method
In the mid-1990s, a doctor and a statistician teamed up to find a simpler solution than X-rays. They developed the Khamis-Roche Method, a mathematical formula that you can begin to use once a child is 4 years old.
Simply plug in a child’s current weight, height, age and parents’ adult heights to predict your little one's eventual adult stature. A calculator does the rest — no radiation required. While it may not work for exceptionally tall kids, it is the most accurate predictor without getting an X-ray.
Mid-parental height method
Most kids grow to about 2 inches of what’s known as their parents’ "mid-parental height," which finds the average of parent’s heights using different formulas for boys and girls. The formula can give you a good idea of your child's height, though it's not an exact science.
- For boys, adult height is calculated by combining both parents’ heights, dividing by two, then adding 2.5 inches.
- For girls, you’d add both parents' heights together, divide by two, then subtract 2.5 inches.
Doubling height at age 2
While there aren’t studies verifying the accuracy of this popular method, it’s a quick way to give curious parents an idea of what to expect. So much growth happens during the toddler years that kids generally reach half of their adult height within the first two years of life.
Simply doubling your boy’s height at 2 years old and your girl's height at 18 months (since girls tend to develop faster than boys) gives you a rough guesstimate of your child's future stature.
Why predict your child's future height?
How tall your child will be is not just a fun tidbit of information. Once you and your doctor know your child’s estimated adult height, you won't worry so much when the inevitable growth spurts and plateaus of childhood and adolescence happen.
And if your child is consistently shorter than the trend for her predicted adult height, your doctor can explore whether an undiagnosed illness or nutritional deficit is to blame.
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