Dear Dr. Lanny:
My 6-month-old baby boy is 27 inches long and weighs 18 pounds, at least according to his most recent measurements at the pediatrician. (Actually, I’m not entirely certain about the length because he didn’t really cooperate to stretch out to be measured.) Are those numbers appropriate for his age? Is there anything I can do to help him reach a healthy size?
A: Well, congratulations, and happy half-birthday to your son. The rest is easy. Unless, you count toilet training, getting into the right pre-K and adolescence.
“How do I get him to be a healthy size?” This is a surprisingly easy question and I rarely find any question to be easy. You get your son to a healthy size by providing good food, a loving and safe environment, and the right genes. (That’s genes, not jeans.)
The first two parameters—food and environment—you can influence; the third, his genetics, are beyond control. I am speaking here about otherwise normal, healthy children, not children with some illness affecting growth.
As you have already realized, measuring infants is an art, and truly good art is really rare. The little ones are remarkably resistant to being straightened out and staying put. Even a great artist like da Vinci would be hard pressed to measure little ones accurately during the first two years of life.
Many children who are genetically destined to be small adults may be quite large at birth and the following few months, but in the second half of the first year of life, they slow down and start to follow their genetic destiny. I’m a perfect example. I was my mother’s second child. My older brother was 6 pounds, 8 ounces at birth, and I was 8 pounds, 6 ounces. Our birth lengths are long lost in history. That was, figuratively speaking, my high point. Both of us wound up at 5 feet 4 inches. Our mother’s fault, as she never quite reached 5 feet.
When you take your child to the doctor for his well-child exams, frequently in the first two years of life and then annually until he moves on to an adult medicine provider, he should always be weighed and measured (ideally naked for the very little ones, or with minimal clothing and no shoes, when he’s old enough to stand). Your doctor, or now his or her computer, will display your son’s height and weight on a growth chart, a very low-tech but extremely helpful aid in evaluating your child’s growth and overall health.
The growth chart gives the doctor your child’s length and weight percentiles—simple to the doctor, but surprisingly confusing to the parental public.
A short lesson in percentiles. Think of percentiles as comparing your son to 100 other boys born on the exact same day as him. A 6-month-old boy who measures 27 inches (your son) would be at the 75th percentile. This means that if you lined up all 100 of those boys in size order, he would be bigger than 75, and smaller than 25. And, yes, he is above average, average being 50th percentile. If you do the same exercise, but do it according to weight, he would be just about the 60th percentile. This suggests that his height and weight are in similar percentiles, meaning that he is in good proportion, neither over- nor underweight.
Children and adults are rarely at the exact same percentiles for length and weight. Being in the 90th percentile for weight only means your child is overweight if his height is in a considerably lower percentile. The goal is to have length and weight in the same or similar percentiles.
It is fascinating to see that for most children the height percentile at 3 years of age, which is when you can usually get an accurate standing measurement, will remain the same for the rest of his or her life. In other words if your son is taller than 50 percent of 3-year-olds, he will usually grow to be taller than 50 percent of adult men (5 feet, 10 inches).
I hope that this makes growth charts and percentiles a bit clearer. If not, please send me a note and I’ll try and do better. For specifics about your child, ask your doctor.
Going back to your question. What is a healthy height? A healthy height is one that is consistent with your genetic destiny. Your child’s height can be pretty accurately predicted using parents’ heights (your doctor can easily show you how to do this), as well as by growth-chart measurements. Both of these methods are quite good, but there are always children who, for one reason or another, do not follow the guidelines.
I’d like to have been taller. I’d still like to know what it would be like to be 6 feet, 2 inches, but I’m not sure I’d like to be that big and try to sit on an airplane. My height has not been a problem. My son, Daniel, is 5 feet, 7 inches, and his brother, Lucas, is 5 feet, 11 inches. Who knows where that came from?
Dr. Alan Freshman, father of two grown sons, practices at Syracuse Pediatrics. Consult your own physician before making decisions about your family’s health care. Send e-mail to him at email@example.com.
Growth charts: For charts to track your own child’s growth, visit http://www.cdc.gov/growthcharts/clinical_charts.htm.
Picture above: © Vojtech Vlk | Dreamstime.com