I loved the way my son fit so perfectly into my arms when I held him for the first time. I could barely imagine him becoming any bigger, much less growing taller than both me and my husband. Maybe if I'd paid more attention to what science says about when a child's future height is determined, I would have realized that I had just given birth to a future broad-shouldered, long-limbed young man who's tired of being asked all the time whether he plays basketball. (For the record: no.)
Although it's far from an exact milestone, a child's future height can generally be predicted by the time they turn 2, according to the Mayo Clinic. Measure your child and double that number, and you'll have a fairly accurate picture of their adult height, with girls being a little shorter and boys being a little taller. So if your toddler is already nearing 3 feet by their second birthday, you can expect to bypass the petite and small departments of clothing stores by the time they hit puberty.
Another formula often used to predict a child's height is to add the mother's and father's height in inches, then add five inches for boys or subtract five for girls, and divide by 2. So a 5'1" mother and a 5'11" father could expect to have a 5'8 1/2" son or a 5'3 1/2" daughter, using that logic. (I tried this formula for both my children, and it's pretty spot-on, though neither of them have yet hit their full height.)
The National Institutes of Health explained that 80 percent of our height is determined by genetics; if you and your partner are on the short side, odds are your children will be, too. At least 700 gene variants affecting height have been discovered to date by geneticists, including genes that control the growth plates in our arm and leg bones.
Genes associated with certain rare disorders can also affect a child's height. As WebMD noted, achondroplasia, the most common form of dwarfism, is genetically based. On the other extreme, a genetic disorder called Marfan syndrome affects the connective tissues in the body, causing people with the condition to grow unusually tall.
Environmental factors can negatively affect a child's growth, too, even if the parents are tall. Nutrition is one of them: As a Tufts University molecular biologist explained to Scientific American, prepubescent children whose diet is lacking in sufficient protein, calcium, and vitamins A and D are likely to be shorter than peers who eat a more balanced diet. (As always, Mom knew best when she told us to drink our milk.)
Moms who smoke may influence their children's height both before and after birth. According to one long-term study published in BMC Pediatrics, Brazilian children whose mothers smoked during and after pregnancy "showed persistent lower height-for-age since birth to adolescence compared to non-exposed." The same may be true when it's the kids who are doing the smoking: A Canadian study of 12- to 17-year-olds who smoked regularly found that male smokers were more than 2.5 centimeters shorter than their nonsmoking peers. Female teen smokers' height wasn't significantly different from that of nonsmokers. (But then again, neither was their weight, noted the researchers — putting to rest the old excuse about smoking as a weight-loss strategy.)
If you have a large family, it's also possible that your youngest children may be shorter than their older siblings. As reported in The Guardian, a British study of 14,000 families found that children's height was strongly related to their birth order and number of siblings. The more siblings a child had — particularly brothers — the shorter the child was likely to be. The researchers suggested several possible reasons for this phenomenon. It's possible that parents of larger families are less able to feed their children well, with the younger ones getting (literally) short shrift. Moms who have multiple pregnancies are also more likely to have health conditions that could affect the growth of their later-born babies.
All things considered, however, you can figure that your child will fall somewhere between or just over your and your partner's heights when they grow up, especially if they eat a nutritious diet. If your child complains about being asked how tall they are, suggest that they try Abraham Lincoln's famous quip about his height: He always said that he was "tall enough to reach the ground."