Age-by-Age Growth: Milestone Madness

What's Normal?

Milestone Madness
Sang An

Today's new parents can easily check their babies' progress against development charts in dozens of books and Internet sites -- a good thing, in moderation. The problem is that parents risk taking too literally this wealth of literature, expecting their baby to crawl at precisely 8 months and to walk at 12 because the guidelines say those are the norms rather than the averages. Excessive chart-watching is not likely to harm an infant's well-being, according to Dr. Brodlie: "At that age, I think it's the parents who are actually harmed."

For mothers and fathers in the throes of milestone madness, the reassuring truth is that individual babies will show a tremendous range of normal development, says Stephen Boris, M.D., a pediatrician who's been in private practice for 30 years in Mamaroneck, NY. "It can be normal to walk at 9 months; it can also be normal to walk at 18 months." Variables like gender and birth order complicate the guidelines in parenting manuals, he says. "First-children girls tend to be very rapid talkers, for example. Second-children boys are often a little bit delayed."

Moreover, the developmental goalposts sometimes move. Until recently, for instance, it was expected that many children would roll over from their backs to their bellies by 4 months of age, but the successful "Back to Sleep" campaign against sudden infant death syndrome has produced many babies who are disinclined to do so until several months later. Barbara Howard, M.D., an assistant professor of pediatrics at Baltimore's Johns Hopkins University School of Medicine, says she no longer pays much attention to this particular milestone, although it persists in baby books. (She does, however, usually recommend 20 minutes of daily tummy time, starting in a baby's first week, to condition muscles for crawling, walking, and other motor skills.)

Pediatricians are largely blasé about height and weight percentiles and tend to be amused by their patients' stories about other parents who trot out these numbers as though they were infant SAT scores. On the whole, pediatricians concern themselves more with the rate of a baby's growth and development than they do with her individual percentile scores. In fact, because height and weight are largely determined by genetics, it's normal for a child to fall almost anywhere on the charts. What's not normal is for any child whose height or weight has registered consistently in one range to show a significant change, unless he's recently been sick.

Because many parents worry unnecessarily about even small fluctuations, some pediatricians, including Dr. Boris, don't address percentile scores unless specifically asked. There is no need, he says, as doctors are unlikely to overlook a baby who is way too big or way too small for his age. Indeed, real problems -- which may be nutritional or behavioral, among other causes -- tend to be obvious at a glance.

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