WHO versus CDC growth charts: WHO cares?

Ah, infant growth charts. Aside from those on your junior year SAT math section, no graph can inspire more fear and concern. FC’s percentile chart looks like a death-defying roller coaster – from the 10th to the 75th to the 25th. Fearlette’s is always at a consistent 20th, but considering her height was in the 75th, her weight to length line is disturbingly close to the bottom of the page.

I hate those growth charts.
According to yesterday’s Wall Street Journal, so do many other parents. Columnist Melinda Beck reports that: 

Parents often worry that their children are too tall, too short, too fat or too thin. These days, however, more kids are measuring “off the charts”—either above or below the standard ranges for height and weight that pediatricians use.

The wide variations are due in part to rising obesity rates, an increase in premature infants who survive, and a population that is growing more diverse. Yet the official growth charts from the Centers for Disease Control and Prevention still reflect the size distribution of U.S. children in the 1960s, ’70s and ’80s. The CDC says it doesn’t plan to adjust its charts because it doesn’t want the ever-more-obese population to become the new norm.

Beck goes on to explain how many are lobbying for the American Academy of Pediatrics to adopt WHO growth charts, as our current ones don’t reflect the growth patterns of breastfed babies. The movement has been going on for awhile, and I think it’s important to understand how the two types of growth charts differ.

The WHO growth charts are meant to act as a normative standard, as they were based on children who fulfilled specific criteria – “proper” nutrition (breastfeeding exclusively with complementary solids starting between 4-6 months), born at a healthy gestational age and weight, living with sufficient socioeconomic conditions, decent healthcare and breastfeeding support, etc. The charts are based on records of children fulfilling this criteria in Brazil, Ghana, India, Norway, Oman, and California between the years of 1997-2003.

The CDC growth charts are simply a snapshot of one general population (the midwestern United States) over 30 years. No babies were excluded based on any criteria. You can think about it like this: the WHO charts are based on an ideal; the CDC charts are based on a time-and-location-specific reality.

I am not a fan of the CDC charts. Just as they do not accurately address the growth trends of breastfed babies,  one could easily say that the current growth charts also fail to reflect the social, ethnic, environmental, and hell, I’ll say it – evolutionary – factors which are contributing to larger babies.

The problem is, neither do the WHO charts – in fact, I fear they will only make things worse.

There seem to be two separate concerns being expressed within this particular debate: one, that breastfeeding moms are being mistakenly informed that their babies aren’t growing sufficiently on breastmilk alone; two, that our nation’s babies are a lot bigger than they used to be, and the growth charts don’t reflect this. These two problems have incompatible solutions. Adopting a chart which skews lighter, as the WHO charts do, might help the breastfed kids seem more “normal”, but it would also make the majority of babies in this country seem disproportionately bigger. If it were an indisputable fact that larger babies were inherently unhealthy, one could argue that categorizing more babies as outside the “ideal” would be a good thing. As far as I know that isn’t the case. There is some correlation between faster weight gain in infancy and later obesity, but this is still a rather tenuous correlation considering the quality of the studies which suggest it. By adopting the WHO charts, I fear we will suddenly see an “epidemic” of “obese babies”; next thing you know we will be putting 4-month-olds on diets.  I know it sounds CoCo Puff Crazy, but check out what the authors of this report from the CDC comparing the two types of growth charts said about the subject:

Clinicians should recognize that the WHO charts are intended to reflect optimal growth of infants and children. Although many children in the United States have not experienced the optimal environmental, behavioral, or health conditions specified in the WHO study, the charts are intended for use with all children aged <24 months. Therefore, their growth might not always follow the patterns shown in the WHO curves. For example, formula-fed infants tend to gain weight more rapidly after approximately age 3 months and therefore cross upward in percentiles, perhaps becoming classified as overweight. Although no evidence-based guidelines for treating overweight in infancy exist, early recognition of a tendency toward obesity might appropriately trigger interventions to slow the rate of weight gain.

I’m not convinced breastfed babies would be immune to the Obese Baby label, either. The WHO growth standards on not based on American children; there are genetic, ethnic, and situational factors that play into growth, weight, and length of babies. We tend to be a rather, er, well-fed bunch; maternal diet can affect the amount of fat and other nutritional content of breastmilk, and the lifestyle of the mother can dictate how much milk a baby receives. An exclusively breastfeeding mom who works full time will likely have a baby who is bottle-fed breastmilk as much or more than s/he feeds at the breast;  studies have shown that it may be more the mechanism of feeding than the type of milk which influences weight gain.

Nor would universal adoption of the WHO charts necessarily negate a physician’s desire for intervention when weight gain plummets downwards. One of the women interviewed for the WSJ piece was a woman whose “5-month-old son, Elias, has slipped from the 50th to the 25th percentile.” Her answer to the guilt inflicted on her by her pediatrician was to consider “taking a leave from her job as an associate professor of human development at California State University, Long Beach, so she’ll be available to nurse on demand.”

A drop from the 50th to the 25th percentile at 5 months might not be seen as a cause for concern if pediatricians were trained in the growth patterns of WHO chart-compliant babies. But I think this quote underscores the problem with any type of growth chart: every situation is different. We don’t know enough about this woman’s story to know whether her doctor was an anti-breastfeeding alarmist, or merely a follower of the Hippocratic oath. (Please note: I am not making any sort of judgment on this mother’s situation, but I also think we need to look at these types of anecdotes critically, as they tend to get used as fodder for the ongoing infant feeding debate. I’m looking at the quote alone within context of the article, and trying to point out that there may be additional layers to the story, and that the solution may not be as simplistic as adopting new growth criteria.) Why would the mom feel the need to quit her job and “nurse more” as the solution? To me, this suggests that the mom feels her time away from the breast is the problem – it could be that the baby has a problem taking a bottle, or the mom has a problem expressing enough milk.I’d also question, since the drop in weight occurred around 5 months, whether adding solids might be a solution. There has been discussion in the medical community about relaxing the “six months exclusive breastfeeding” rule to “four months exclusive” at which point solids can be added to the diet, based on individual readiness and need. Perhaps this baby is one who is both ready and needy for a bit more sustenance. This has nothing to do with the adequacy of his mother’s milk or her employment status. Nor does it have anything to do with formula supplementation or which growth charts are being used. 
I understand the argument that the current charts are outdated in pretty much every way possible, and need to change. But I think a more helpful solution would to be to stop being slave to the percentiles, and instead use them – perhaps the CDC ones for formula fed babies, and the WHO one for breastfed babies – as merely a guide. If a baby is healthy, growing, and meeting developmental milestones, then who cares if she is in the 10th or the 80th? Especially if our only choices are to compare that a baby living in 2012 in Tuscon, Arizona to either some statistical hybrid of Gambian and Norwegian babies, or one from Wisconsin in the 1970s. Let’s not lose sight of the fact that the current system judges all babies (and parents) by unfair standards, and not allow this to be more kindling for the breast versus bottle pyre.

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