Why pediatricians are abandoning percentiles.
With just three words, Christine Coan’s pediatrician reduced the Philadelphia-area mom to tears. The doctor explained that in just the 7th percentile for weight, 12th for height, Alex – who breastfed until he was eight months old – was too small.
“I was devastated. I was embarrassed,” Coan said. “I got this pit in my stomach like I was a failure.”
Coan isn’t crying any more. These days, the topic of her son Alex’s height and weight leaves her spitting mad.
Yes, Alex was, in her words, a “shrimp,” just like she herself was growing up (Coan today is just 5’2″). But his low weight was due in part to the fact that Alex had just begun walking, his body quickly burning through the Gerber Graduates he wolfed down at each meal.
And he was simply growing at his own rate. Now almost four, Alex is neither the shortest nor the tallest kid in his class. Healthcare practitioners have since confirmed what Coan suspected: her doctor’s interpretation of the percentile charts was dead wrong.
Sour experiences like this have led to a trend in the pediatric community away from quoting percentiles to parents. It’s not that percentiles themselves are bad, just that improper reading can be unduly upsetting and that the charts used in the U.S. have certain limitations, especially for breastfed babies like Alex Coan.
According to the World Health Organization (WHO), the fatal flaw of the percentiles used by most U.S. pediatricians to chart growth is this: they compare children to other American children, and other American children are, well, big. Thanks to the U.S. obesity crisis, many of them are in fact way too big. And that leads some parents of smallish children to look at the charts and believe their kids are undernourished.
Instead of looking to the percentiles, we should consider a new kind of chart, says the WHO. By their metrics, we would judge children’s progress in comparison not to each other, but to a fixed ideal. Advocates of the WHO model say that data developed in a study of children given the very best care and raised in the very best circumstances provides a standard less arbitrary than a percentile based on the growth of random children who may or may not be healthy.
But here in the United States, plenty of pediatricians still use the old percentiles, and the U.S. government approves. Introduced in the late 1970s by the National Center for Health Statistics (NCHS), the weight and height charts now fall under the umbrella of the Centers for Disease Control (CDC), which put out an update in 2000. The CDC says these new, detailed charts are optimal for tracking growth and preventing childhood obesity.
But health organizations worldwide have accused the CDC of failing to keep pace with the WHO, which put out its own revamped charts in 2006. The WHO study, which began in the late ’90s and ran through 2003, looked at more than 8,000 children spread across the world, including kids in the United States, Brazil, Ghana, India and Norway. Researchers limited their study to families who fit “specific behaviors that are consistent with current health promotion recommendations (e.g., breastfeeding norms, standard pediatric care and non-smoking requirements).”
A CDC employee, who preferred not to be named, said the WHO standards will likely not be adopted in the U.S. because they’re based on countries where breastfeeding is the norm. Even though the CDC encourages breastfeeding, there has been no effort to use breastfed babies for its charts. Instead, for its latest update, the CDC used data from “five nationally-representative studies” conducted between 1963 and 1994.
Researchers used no controls to maximize the numbers of breastfed babies included in the study, reports a study published in the American Society of Nutrition in January 2007. In fact, a large portion of the data was taken from the Pediatric Nutrition Surveillance System, a project started in 1972 to track children in low-income households using publicly funded health and nutrition programs – a far cry from the WHO study’s standards.
So, why would that matter? Well, because breastfed babies often have a different growth curve than formula-fed babies. A healthy breastfed baby can begin to thin out by six to nine months and become quite lean by nine to twelve months. By the CDC standard, such children sometimes appear underweight.
Posing just this issue to the CDC in the September 2002 issue of Pediatrics, the Official Journal of the American Academy of Pediatrics, Dr. Mary Bender of Norwich, Vt. said:
“Unless practitioners use anticipatory guidance to warn parents about this predictable phenomena (and until the World Health Organization charts are available), they will spend the six-month visit, rather than congratulating parents on having exclusively nursed their infants, trying to reassure away their apparent growth faltering (or worse – beginning a failure to thrive investigation and supplementing with formula).”
Reached recently by phone, Bender said she continues to lack faith in the CDC guidelines: “These growth charts do not reflect how babies grow,” she said frankly.
Michele Crasa saw her son Nicholas shoot to the top of the height charts around his first birthday. “These growth charts do not reflect how babies grow.” He was at the 90th percentile for length while his weight was dipping. She said the words “failure to thrive” from her pediatrician threw her into a frenzy. She was pushing Nicholas to eat so hard that the toddler began to become resistant. Each time Crasa put food on the tray of his highchair, Nicholas would refuse. Each time he refused, she’d pull out one of his favorites, because she was desperate to make him eat.
When she returned to the pediatrician for his fifteen-month appointment, his weight was climbing back up the charts. But the doctor had a new criticism for Crasa. “She called me a deli mom,” Crasa said with a sigh. “She said when he doesn’t want something I shouldn’t give in and make him whatever he wants. It’s like I can’t win with her.”
And parents want to win. They want to do the very best for their kids. So they get obsessive over the charts, as if they were test grades.
“So often, parents get attached to ‘My kids is at the 10th percentile, and oh, I wish they were at the 90th,’” Bender said. Bender recalls a parent who was 5’3″ worrying because her child’s height was on the shorter end of the spectrum.
“I’d tell parents, ‘This chart has absolutely nothing to do with the health of your baby,’” she said. “The charts are just not based on the optimal way to feed babies. Considering the issues in this country with obesity in children, what are we trying to do here?”
But percentiles continue to be popular. Included in the packets sent home with most new moms is a CDC growth chart, and the Internet is brimming with “growth calculators” that require minimal information to spit out a number that’s supposed to evaluate your child’s health.
Plotting a child’s weight and height should only be a starting point for pediatricians, says nurse practitioner Nancy Eschenberg, who’s spent her career in family practice in upstate New York, including seven years in a pediatric office and two more working with kids with developmental disabilities.
“I view it as a screening tool,” Eschenberg said. “You to need to compare it to what a child’s growth trajectory is – in other words, if they’re on the 10th percentile, you want them to continue on the 10th percentile or pretty near because that’s their normal trend.”
“You have to look at genetics,” she says. “If you have a father who’s 5’11″ and a mom who’s 5’3″, you’re not going to have a kid in the 95th percentile.”
A jump or drop should be watched, Eschenberg continued, but practitioners can’t immediately raise the alarm. “There are growth spurts children will go through,” she noted. “There are times kids chub up and then they shoot up.”
If a child’s height or weight seems to be fluctuating drastically, Plotting a child’s weight and height should only be a starting point for pediatricians. Eschenberg says she might ask the parent to make another appointment sooner rather than later. She’ll talk with the parent about a child’s eating habits, try to suss out whether a child is drinking more than he eats or if a little girl is running off all of her excess energy.
Bender and Eschenberg prefer to tell parents, “Your child is developing well,” or “Your child is a little too thin; let’s talk about this.” They don’t quote percentiles.
It’s a practice being picked up by an increasing number of doctors frustrated by parents pushing for the secret to attaining the top percentiles – parents who still think higher is better. That’s why many doctors are even dropping the word “percentile” from their lingo. Finally, more pediatricians are looking past the dots charted on a government-approved graph to the baby in front of them.
Photo Credit: Melissa Drenzek