You've probably heard your toddler's pediatrician tell you what percentile he falls into on the growth chart. This number is determined by comparing his height and weight to that of other toddlers his age to see how he measures up. Pediatricians plot your child's growth on the charts to see if they stay on the same curve as they grow and it also helps monitor their weight in case they gain too much or aren't putting it on as they should.
How They Work
Down one side of the chart is height in inches or weight in pounds and along the bottom is your child's age in monthly increments. Each time his pediatrician measures his height or weight, he records it on the chart on the corresponding month of his age at the time. The doctor then compares your toddler's size to others his age to find out what percentile he falls into. For example, if he is in the 25th percentile, he is, on average, larger than a quarter of other toddlers his age and smaller than 3/4 of toddlers his age.
Role in Diagnosing a Health Problem
Height to weight ratios are important for pediatricians because they help them watch your child's growth. Toddlers who don't keep up with their peers or who suddenly fall off the charts or their own curve might have health issues, including failure to thrive. This might indicate a food intolerance, nutrient deficiencies, digestive problems or a chronic health condition such as a respiratory issue. On the other hand, a toddler who starts gaining too much weight is at risk of obesity, diabetes and even cancer later in life. If this happens, your child's pediatrician can help you figure out a way to get your toddler back where he should be.
Body Mass Index
Height to weight ratios are valuable for determining your toddler's body mass index, or BMI. This number helps you and your toddler's doctor detect a weight problem. Your child's height helps you figure out a range for a healthy weight. If his BMI is too high, you'll know he is overweight, but if it falls in the normal range, you'll know that he is healthy, even if he seems too thin or too chunky. Many doctors only use BMI charts for adults, but some pediatricians use it with young children as well, due to the increase in obesity among American children.
If There's a Problem
If the height to weight ratio indicates that there might be a problem with your child's growth, his doctor will likely recommend additional testing. If your toddler is underweight and can't seem to catch up, he may have him checked for conditions such as celiac disease, cystic fibrosis or a liver disorder. Once the cause is determined, treatment can help your toddler get back on track and back on his growth curve. If your toddler seems to be gaining too much weight, his pediatrician will likely talk with you about his eating habits and make suggestions about satisfying his hunger with a reasonable number of calories.