Who is my child being compared to on growth charts?

Your child's doctor or provider uses growth charts as an important tool to understand your child's general health <<link-growth chart>>. He or she can quickly see how your child is gaining and growing in terms of the inches and pounds your child has added. But also how those measurements compare to other children the same age. If a child has genetic or other problems (like Down syndrome or being a premature baby, for example) the information can be compared to children who are similar. Importantly, repeated measurements provide a more complete picture — creating a graph with more information that can tell you what to expect in the future.  

Who is my child being compared to?

A critical, but often ignored, question is who are these children my child is being compared to?  The first attempts were less than 50 years ago, when the US National Center for Health Statistics compiled the information from a cross section of American children and created the curves so we could see if children were growing adequately. In 2000, the US Center for Disease Control and Prevention (CDC) revised the graphs with information collected from over 18,000 Americans over 2 years of age who were involved in the  National Health and Nutrition Examination Survey (NHANES), with wide racial and ethnic diversity.

The World Health Organization has replaced the curves for infants and toddlers, instead looking at the optimal growth in 8440 healthy breastfed infants and young children from widely diverse ethnic backgrounds and cultural settings (Brazil, Ghana, India, Norway, Oman and USA). By selecting healthy children living under conditions likely to favor their full genetic growth potential, this sets a higher standard, and as a result these growth charts have been widely adopted.

But again, those growth curves don't reflect everyone's potential. We can't use them for the premature baby in their first years of life, because it often takes them a long time to catch up (typically, a year for every month they're early). So a 30 week infant, 2 1/2 months early, needs 2 1/2 years to catch up. Some of them don't fully catch up in height, though they might be in weight, which leads to them being overweight.

With our continued concern about children becoming overweight, there are also growth curves for BMI (Body Mass Index) that help track weight gain in relation to height; and there are also growth curves for a healthy child's head circumference to detect possible problems with brain growth. Additionally, growth curves have now been constructed for a number of genetic and developmental conditions such as cerebral palsy and Down, Turner, and Prader-Willi syndromes.