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By Nancy Gottesman
Eleven years ago, when my son was a 2-year-old, I asked our pediatrician which percentile he fell into. I suspected he was large for his age and wanted to hear the number so I could be the proud parent of a “90 percentile” baby. Her reply, however, startled me. “He’s perfectly healthy and he’s thriving,” said the doctor. “What do you care how he compares to 10,000 white kids in Ohio?”
She did end up telling me, of course, but her point was a good one: If we know our kids are growing and developing on track, why do we look upon those pediatric percentiles as some sort of report card? “Parents need to understand that everything between the 3rd and 97th percentiles is normal,” explains David Wolfson, M.D., medical director of Children’s Community Pediatrics, which is affi liated with Children’s Hospital of Pittsburgh of UPMC. “Growth charts are an important diagnostic tool, but the actual percentile number may be the least important part.”
What is a percentile?
In 1977, the Centers for Disease Control (CDC) developed growth charts as a clinical tool for health professionals to determine whether a child was developing adequately. After collecting thousands of U.S. children’s height and weight stats since the 1960s, the CDC was able to show a range of measurements on one chart, using a curved line to represent a percentile.
In 2000, the charts were revised to include BMI measurements and to reflect changing ethnic populations in the U.S. “When the charts were initially devised, they were based on middle-class white kids,” says Katrina Parker, M.D., director of pediatric endocrinology at the University of Texas Medical Branch in Galveston. “Now the charts represent today’s population better.” Your pediatrician uses different sets of growth charts based on your child’s age and gender.
One set of growth charts covers babies and toddlers from birth to 36 months, since they grow at a different rate than toddlers and older kids. Another set covers kids 2 to 20 years old. Still another set of special growth charts are used for children with health conditions such as Down’s syndrome. And in each age or health category, there is one set of charts for boys and one for girls because the genders grow at different rates.
At your annual well-child checkup, your doctor will plot your child’s height and weight along one of the curves on the appropriate growth chart. This plotting determines the percentile that shows where your child’s measurements fall when compared to others. The higher the percentile, the larger the child in comparison to other kids of the same gender and age. The lower the percentile, the smaller the child. For instance, a 3-year-old girl whose weight is at the 25th percentile weighs the same or more than 25 percent of girls her age and less than 75 percent of them.
High or low isn’t what matters
“The growth charts are just one tool pediatricians use to help gauge whether a child is growing properly and as expected,” says Wolfson. Falling into a high percentile doesn’t mean that your child is healthier, nor does it mean your child has a growth problem if he falls into a lower one. What is important is that your child—whether he falls on the 5th or the 95th percentile curve after infancy—continues to follow that curve as he gets older. “It’s when a child deviates from the curve that we investigate further,” says Wolfson. “We want to find out if there’s a problem.”
This is why it’s vital that you bring your child to the pediatrician for an annual checkup. By comparing your child’s current spot on the growth chart with measurements from previous visits, your pediatrician will be able to ascertain whether your child is growing normally. Here are some growth chart deviations that indicate something may be amiss:
• When weight or height percentile changes from a pattern it’s been following. Let’s say your child’s height and weight have followed the 65th percentile line pretty consistently for fi ve years. At age 6, both height and weight suddenly drop into the 35th percentile. An unexpected slowing in a child’s growth pattern could indicate a health problem. “Ideally, a child should be growing along a curve,” says Parker. “Many things infl uence growth—nutrition, exercise, psycho-social factors, hormones, genetics—and we’d want to find out what caused the change.”
• Gaining weight at a faster clip than she’s gaining height. Your doctor may want to discuss your child’s diet and exercise habits if she’s in the 30th percentile for height, but the 80th for weight. (That is, she’s taller than only 30 percent of her peers, but weighs more than 80 percent of them.) “By age 4 to 5, a child knows where the snack cabinet is,” says Wolfson. “This is the age when weight may curve up more than it should.” (In addition to height and weight growth charts, pediatricians also use BMI growth charts beginning at the age of 2.) On the other hand, if your daughter has followed this curve consistently over the years, your doctor may conclude that she’s heavier than most kids her age due to genetics and that she’s growing normally.
• A gain in height but not in weight. This means your child is getting taller but isn’t gaining weight proportionately. “If weight is falling off, the fi rst thing we want to fi nd out is whether the child is getting enough calories,” says Wolfson. If it’s determined that he is getting proper nutrition, doctors would want to examine whether a child is absorbing the calories or has an intestinal abnormality. Again, this may also be the child’s normal growth pattern depending on genetics.
The ideal percentile for your child
Even if there is a change in your child’s growth pattern, this by no means indicates a problem. A growth chart is not your pediatrician’s sole diagnostic tool— it is a springboard for further discussion or investigation. “The information on the growth charts provides an opportunity to talk about the pediatrician’s expectations for a child’s growth,” says Wolfson. “For instance, if a child’s height curve is fl at compared to the weight curve, I’ll discuss nutrition and getting the child outside to play more with the parents.”
Pediatricians use the growth charts to help evaluate the big picture, including what part environment and genetics play in a child’s developmental milestones. “A parent may say, ‘My child is too small—he’s in the 3rd percentile,’” says Parker. “But we [pediatricians] look at genetics, and if the parents are small, the 3rd percentile may be normal for that child.” Same with the 99th percentile or the 1st—somebody has to be the tallest or the smallest.
It’s the rate of growth that’s important. If your child is growing on track and according to your pediatrician’s expectations, there’s nothing to worry about. “If genetics dictate that your child is supposed to be in the 25th percentile, for example, then we want him to continue to grow at that rate,” maintains Parker. “The ideal percentile is what is ideal for your child.”
Help your child grow
Your child’s growth pattern is largely determined by genetics. “Assuming your child is growing normally, we can predict how tall he’ll be at age 20 using the growth charts,” says Katrina Parker, M.D., director of pediatric endocrinology at the University of Texas Medical Branch in Galveston. For instance, a 2-yearold boy who is 37 inches tall is forecast to be six-foot-two by the time he’s 20, if he continues to follow the 95th percentile curve on the CDC’s growth charts.
A 2-year-old girl who is 34 inches tall is estimated to be about five-foot-four by the time she’s 20 if she continues to follow the 50th percentile curve. “But things can change,” she confirms. “Nutrition, exercise, diseases and medical treatment can all affect growth.” Your child’s growth depends on a healthy diet, regular physical activity and good sleeping habits, so make sure your child gets enough of each. Remember, too, that pushing extra food or exercise will not boost the height of a child who is genetically predisposed to be short. “Your focus should be on healthy habits,” urges Parker. “We can’t all be basketball players.”
Nancy Gottesman’s 13-year-old son, Robby, is now five-foot-nine—four inches taller than she is. He weighs 140 pounds, which is her goal weight.
ORIGINALLY PUBLISHED IN TODDLER MAGAZINE, HOLIDAY ‘08
PLUS: How to help your toddler grow.