My Ob Said My Baby Has a Big Head
The Dubious Organization for Measuring the Size of Your Baby's Head
Why so many parents are mistakenly told that their kid has a massive noggin.
My daughter Mary was a good for you piddling girl at nativity: 7.eight pounds and slightly on the tall side. But her head circumference was almost off the charts. At 14.2 inches around, her skull was in the 96th percentile of all newborns. "She has a huge brain!" I crowed to anyone who would listen. "She's going to be brilliant!" I was joking, of course, but I was also secretly a little proud of the kid'south massive noggin.
Doctors measure a infant's head at every appointment in the first few years of life, and there are a lot of appointments. Mary bobbed around a bit on the charts as she grew, but her head stayed impressively aplenty. At her near contempo date, her doctor printed out a nautical chart from the World Health System that showed my now 2-year-old'due south head was still bigger than 93 out of 100 babies her historic period.
By that time, nonetheless, I'd started to suspect that she was non actually the behemothic-skulled wonder I'd been led to believe. A curious number of my shut friends with new babies seemed to be bragging about the aforementioned distinction, for one. "His head is enormous!" one fix of houseguests told us, showing off their adorably chunky infant. A few weeks afterward, another sometime friend stopped by for brunch and told us his year-old son's caput was every bit large as they come. Yous only need to browse a few parenting bulletin boards to see that the internet is teeming with parents exclaiming over their kids' prodigious skulls. When I asked the parents on Slate Slack almost their babies, several people immediately piped up: A 1-year-sometime at the 97th percentile, a two-calendar month-sometime at the 96thursday. 1 editor has a toddler whose caput is at the 96th percentile and body weight at the 18th. It was starting to experience similar I lived in a bobblehead version of Lake Wobegon, where all the children'southward heads were above average.
But information technology turns out that this phenomenon is actually the result of some general confusion about what constitutes an oversized infant head. When Carrie Daymont, an banana professor of pediatrics at Penn Country, was a resident in medical school, she found herself having conversation after conversation with parents whose infants' heads measured equally abnormally large or fast-growing. In the clinical context, heads at the extreme upper finish of the growth curve are crusade for legitimate concern, not cheeky gloating. She wondered: Were this many babies at risk for problems like brain tumors or cysts, for which the measurement for macrocephaly—an abnormally big head—is meant to screen? Or were the charts themselves inaccurate?
What Daymont found when she started looking into this will trounce the pride of whatever parent who relishes bragging about their offspring's colossal cranium. She started with a data set that included the head measurements of 75,000 pediatric patients spanning 3 states, and compared those measurements to the WHO nautical chart. If the WHO nautical chart is accurate, and then v percentage of babies should exist in a higher place the 95th percentile, ten per centum above the 90th percentile, then on. That's not the instance. From nascency to age 2, fully fourteen percent of babies were to a higher place the 95th percentile, according to the WHO's chart.
Past age 2, 18 percent of children were above that cutoff—which means it'southward not really the 95thursday percentile, simply the 82nd. "Nosotros're talking well-nigh small differences in head size," Daymont told me. "Just the 97th percentile on the WHO nautical chart, I very much doubt that's the 97th percentile of babies in the United states of america." Her findings were published in the journal Pediatrics in 2010. And she's not the but one to persuasively question the accurateness of the way nosotros assess head size. I 2013 study, for example, suggested that a previously suspected connection between autism and fast-growing brain size may instead reflect inaccurate caput-circumference standards, rather than an actual design of atypical growth in children with autism.
The WHO curve, published in 2006, is based on measurements of children in half dozen countries, including the United States. The Centers for Disease Control and Prevention started recommending that pediatricians use the WHO curve to assess children from birth to historic period 2 in 2010, and it is at present the widely accustomed standard amid pediatricians in the United states of america. The CDC also maintains its ain curves. Only those curves, too, failed to reverberate the actual infant heads Daymont surveyed: 12 percent of 1-year-olds measured above the 95th percentile, for instance. The CDC's curve is also steeper than the WHO'south, which means it's likelier that a kid will expect like his head size is fluctuating in size between appointments, which could prompt fifty-fifty more than unnecessary worry and medical treatment.
How could this chart be so askew? The WHO chart's premise is that all healthy, chest-fed, economically stable children grow in basically the aforementioned way, no affair who they are or where they are born. Only the ane-caput-size-fits-all approach doesn't reflect reality. Head size seems to vary slightly between populations, possibly due to genetic or epigenetic variations. Researchers who compared the WHO curve to actual head measurements in 55 countries and ethnic groups in 2014, for example, concluded that the use of a single international standard for assessing head circumference simply doesn't make sense. And American babies seem to exist far enough off the international standard that Daymont believes the WHO curve may not be the correct one for babies built-in in the United states.
If this line of research carries an uncomfortable whiff of eugenics for you, fear not: In that location are some studies that show very weak relationships between intelligence and both head circumference and height, but we cannot straight infer anything meaningful about an individual's or ethnic group's intelligence based on those measurements. The reason doctors wrap that little measuring tape effectually babies' skulls millions of times a twelvemonth is not to give parents a fun stat to jokingly brag most, but to screen for serious abnormalities. So in this age of widespread parental obsession with the size of their babies' domes, it'southward amazing how few of u.s.a. know what "normal" really ways.
Source: https://slate.com/human-interest/2018/01/why-so-many-parents-are-mistakenly-told-that-their-kid-has-an-oversized-head.html
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