Growth Percentiles - What Do They Mean?

Growth charts that your doctor uses represent the average weight, height, or head size of a bunch of normal children. So, your child is being compared to the national averages of other children in their age group.

On the growth charts you will see the percentile lines running parallel to each other. If a child's weight is at the 50th percentile line, that means that out of 100 normal children his or her age, 50 will be bigger and 50 smaller (i.e. he/she is falling right in the middle). Likewise the 86th percentile means your child is bigger than 86 and smaller than only 14, compared with 100 children his age. There are separate charts for weight, height, and head circumference.

To see if your child is too skinny or overweight, there is a 'weight for height' chart or a BMI index, which tells you what percentile the weight is for a child who is that particular height. Decreasing percentiles in this area is often the first sign that a child is taking insufficient calories. Depending on the extent of the poor caloric intake, the child could begin to get stunted -- the height begins to fall off the growth chart. Lastly, and this takes a long time to happen, the head growth slows down, indicating not enough calories for the brain to grow at a normal rate.

The growth percentiles by themselves don't say much. What really matters is the velocity of growth. A normal velocity of growth means the child's growth points will closely parallel the percentile line above it on the chart. They usually don't worry about insufficient (or excessive) growth until a child's growth velocity has crossed at least two percentile lines (e.g., from above the 90th to below the 50th percentile).

Additionally, if a child's weight, height, or head size is below the 5th percentile, we might also call them small for age. In that case, what's most important is to see if the growth points parallel the 5th percentile line (meaning growth velocity is normal) or if the child is falling further behind (which is more concerning).  Anything under the 3rd percentile line in children under 2 years is generally considered failure to thrive and is cause for concern.

Some parents obsessively follow the growth curves and worry unnecessarily about insignificant deviations from that perfect line on the chart. Try to remember that all kids are different and the charts and percentiles are used as a guideline only.  Does your child appear otherwise happy and healthy? Is she making nice developmental progress? Is she taking in at least some protein (milk, yogurt, eggs, meat)?  If yes, to any of the above questions, you likely don't have much cause for concern.

At any rate, you can use the following growth percentile calculators to check your baby or child's growth. Use the one on the left for infants (babies under 2) and the one on the right for children (kids over 24 months).

 Infant Growth Percentile Calculator Child Growth Percentile Calculator

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