Go read the Disclaimer again. I am not a doctor. This is not medical advice. Seriously.
The charts have a shady history.
The charts consult for measurements at well baby visits generally reflect more formula fed (or at least formula supplemented) babies than breastfed babies. No charts exist for exclusively breastfed babies (yet -- the WHO and the CDC are working on developing them). These charts reflect percentile rankings for normal children -- some children are not included on these charts because they were born very early, at a very low birth weight, or have other special health care needs, etc.
The entire range on the chart is considered normal. Heights may or may not significantly differ between formula and breastfed babies, but weights definitely do; formula fed babies are typically fatter. A third chart, which shows height and weight related to each other, is a chart that tall breastfed babies will fall off the bottom of quite quickly. That's because they are being compared to older formula fed babies who are continue to get fatter over time. Many health care providers do not consult this chart for breastfed babies; I've never heard of one worrying about it. While one might worry about a formula baby that fell off the bottom of this chart, if the baby is tall, similar concerns apply.
Measurements are rarely as accurate or precise as one would wish. The height meeasurement is particularly difficult to reproduce accurately. And if the baby is weighed on different scales or, worse, with different amounts of clothing on (they should be weighed naked, which means no diaper; a soaked disposable can hold a lot of water), significant weight "loss" can result from the differences. We've also seen huge transcription errors (over a pound) made between reading the scale and entering it on the computer. If people are panicking because your baby lost weight, have the baby weighed a second time, and read the scale yourself.
Copyright 2006 by Rebecca Allen.
Created February 4, 2006 Updated February 23, 2006