Parents often wonder if their children are growing normally. As a pediatrician, I spend a lot of time talking with families about body mass index (BMI) and whether or not a child is at a healthy weight. But just as often, parents and kids want to know if they are growing in height normally and how tall they are going to grow up to be. While nothing is certain, it turns out that we can predict adult height in kids ages two and older with a reasonable degree of accuracy.
After about two years of age until puberty, children tend to follow a constant genetically determined percentile curve on the growth chart (see Box 1 and Box 2). Growth occurs at a rate of about 2 ½ inches per year throughout childhood until early adolescence, when preteens achieve a peak growth velocity of about 4 inches per year. The growth spurt starts at about nine to 10 years in girls and peaks around 11 ½ to 12 years. Peak growth velocity typically occurs about 18 months before the first menstrual period; at the time of the first period a female is within 1 to 2 inches of adult height. The male growth spurt generally starts at 11 and peaks around 13 ½ years. Growth continues into mid-adolescence for females and well into late adolescence for most males. Closure of the growth plates marks the end of growth.
In addition to following a child’s percentile on the growth chart, you can predict a child’s adult height based on the height of a child’s mother and father. A female will grow to be about the height of: [the mother’s height (inches) + (father’s height (inches) – 5 inches] / 2. A male will grow to be about the height of: [the mother’s height (inches) + (father’s height (inches) + 5 inches] / 2. Most kids will fall within this number plus or minus about 10 percent.
Many environmental factors influence whether a child achieves full genetic growth potential. For example, while moderate levels of physical activity benefit growth, intensive physical training during childhood can negatively impact growth. Athletes who are most affected are those who engage in intensive training more than 18 hours per week and who restrict or limit calories. Elite youth athletes are not the only children at risk for growth delays. Any preadolescent who shows poor weight gain prior to peak growth velocity is at risk for decreased adult height. Likewise, an overweight child who goes through puberty early due to the effects of excess weight is also at risk for decreased adult height. We’ll discuss this issue in more detail in tomorrow’s blog: What is Normal Growth? Part 2