Sunday, February 4, 2007

Infantile Metrics

Is. had her six month check-up on Friday morning, which meant we learned the new set of measurements. This percentile, that percentile. Head circumference: 35th. Weight: 28th. Length: 49th. Percentiles are a relatively uncomplicated normative system for babies: their first (or second, after APGAR) grades. A kind of IRE (Infant Record Exam).

Fortunately, as of Friday, Is. will now have one set of scores. Throughout the first six months, she had two sets, each corresponding to a different age: one actual, one gestational. Against her actual peers: 15th. Against her gestational peers: 53rd. At six months, we're told, her earliness starts to matter much less, and her development is now calibrated against others born in early August. This means she's being scored against full-term babies. Unfair, of course.

All along, I've been intrigued by the scoring, but not because I get worked up about how her head size compares (I'm probably in the 99th percentile both for noggin and nose, so it's reassuring that she's not yet topping out either of those charts yet). The intrigue, in part, involves the way the chart, onto which the measurements are graphed, shows shaded areas--zones of risk related to patterns of measurable development.

I suppose there is a lot more that could be said about this, but I mention it only because I've been giving it some thought since Friday. It's sort of bizarre, on the one hand, and practical on the other. And, as Collin has suggested to me, an expanded array of percentiles could be the conceptual basis for one hilarious comic. But, until I can draw better, I'll just keep it in mind, and look forward to plotting the new evidence of growth when we let the pediatrician tangle her in scales and rulers in another three months.

Posted by Derek Mueller at February 4, 2007 1:45 PM to Under a Bushel