Chances are, one of many things your pediatrician will do at your child’s check up is plot his/her height and weight on the growth chart, and tell you what percentile your child falls into on that chart. But what should you do with this information? And what does that percentile mean?
This first thing to know is what growth charts are and how they are made.
There are many growth charts available. The 2 main charts, which you will most likely encounter at your doctor’s office, are the World Health Organization charts for babies, and the Centers for Disease Control charts for older kids.
The WHO charts are based upon longitudinal data gathered from babies in 6 different countries, including the United States. These babies were raised under what the WHO considers optimal conditions to support growth, including the fact that they were exclusively breastfed for the first 4 months of life and continued breastfeeding up to 12 months. However, these charts work just as well for formula fed babies too.
The CDC charts are references for typical growth patterns in children in the U.S. only, therefore the CDC recommends using the WHO charts for babies aged 0-2. For children aged 2-20 years, the CDC growth charts are recommended (which you can see here, under the section “Children 2 to 20 years“). There are separate charts for boys and girls, premature babies and children with a variety of syndromes including Down Syndrome and Turner’s Syndrome. Other organizations and companies have released their own growth charts but these are not routinely used or recommended.
Growth charts are useful tools for clinicians to look at patterns of growth in the context of a child’s overall health.
Since it heavily relies on this data pattern, one data point in time is not entirely useful. For babies, we can watch to see if they are gaining the expected amount of height and weight. Head circumference is also tracked in this age group. A rapidly growing head may signal a need to further evaluate. For older kids, we can use a child’s mid-parental height (the average of the parent’s heights plus 5 inches for boys and minus 5 inches for girls) and see if they are on target to meet this genetic potential. These charts also help us look at body mass index to assess if the child’s weight is appropriate for their height and age.
Parents are often given their child’s parameters in percentiles. This means that a child at the 50th percentile is right in the middle with 50% of kids smaller and 50% bigger. Not all children are going to be right on the 50th line, so don’t worry. To be clear on the math, sometimes you may hear of a child being at the 98th percentile of growth. That means they’re bigger than 98% of children, with just 2% of kids bigger than them (98+2 = 100). Regardless of their percentile, what is more important is that the child follows his or her own curve, implying that growth is occurring at the expected rate.
So as a pediatrician, what do I do in my office?
The first thing I look at is the child’s length/height. The reason for this is that typical babies/children without any underlying medical conditions – who are getting appropriate nutrition and have appropriate amounts of growth hormone – will be at a height around expected for their genetics. I often get parents of shorter stature who are concerned about their child’s height, and my response is that “apples don’t fall far from the tree.” If a child is growing at an expected rate on a percentile line that makes sense based on their genetics, I then look at their weight (more on short stature in a moment).
If a child is having expected weight gain (meaning they are following their percentile line) I look to see if this is a good weight for their height. A quick check of the BMI can tell you this. There are certainly kids who are petite or husky, but the designated range of healthy BMI is from the 5th percentile to 85th percentile, so many weights can be acceptable for a given height. Therefore, if your baby is healthy and following his/her own chart for all parameters, it doesn’t matter if they are bigger or smaller than their peers.
A word about short stature.
Oftentimes a child around 7, 8 or 9 years old may look to be shorter than expected based on their mid-parental height. Sometimes this is due to constitutional growth delay which is basically what we know as being a “late bloomer.” These kids go through puberty later and make up their growth when they are older. Puberty is a time of rapid growth and then closure of the growth plates so if puberty comes later, kids grow for longer. Certainly if there is a concern about your child’s height or growth velocity, it’s time to have a discussion with your pediatrician. Sometimes a simple hand x-ray to look at the growth plates can let you know if your child’s growth is behind his/her chronological age, hence the likelihood of constitutional growth delay.
Another factor in growth patterns is that some kids are extremely picky eaters and don’t take in enough calories or nutrition to grow properly. When this happens, their height will slow down but that usually won’t occur until there’s an already noticeable lack in weight gain. For children who are not gaining weight and their height is suffering, a trip to the nutritionist to discuss ways to gain weight may be necessary. Of course, a proper evaluation by the child’s pediatrician to rule out other causes of poor weight gain is the most important to starting place.
When in doubt, or when you have concerns, your best course of action is to first consult with your child’s doctor about their growth. It’s a standard practice for their doctor to track this data, so they can provide you with your own child’s growth chart if you request it, if they haven’t provided it already. It’s ok to ask for further explanation of the chart if you don’t understand what you’re seeing, since it can be confusing upon first glance. And as I said, the apples don’t typically fall from the trees – looking back at one’s own growth, puberty, and family’s growth patterns can be a useful insight into what may present in your own child.