There’s one thing you can expect at every well visit: Your baby will be weighed and measured. But what do those weight, length, and head-size numbers really add up to? Here’s how to make sense of infant growth charts — no med-school degree required.
Why doctors use them
Growth charts are just one of the pediatrician’s tools to make sure your child is growing normally. They help doctors keep tabs on your tot’s growth over time and monitor any conditions they’ve been following. Your child’s doc is also on the lookout for any drastic increases or decreases over a short period of time (more on that below), even though it’s often totally fine to have a not-so-average growth curve.
How infant growth charts are devised
The standard charts that pediatricians use are developed by the Centers for Disease Control (CDC) and based on national surveys of US children, both breast- and formula-fed. One set of charts is for little ones from birth to 36 months, using recumbent length (measured when an infant is lying down) and weight on a beam-balance scale or a digital scale (both of which have a tray on which your peanut is placed). The other set of charts is for children from two to 20 years old, which uses standing height and weight. In addition, there is a separate chart for premature babies (although not all doctors use it) and others for infants with special conditions, such as Down syndrome. All the growth charts are different for boys and girls because males tend to be larger.
The percentiles you’ve heard so much about are derived from average heights, weights, and head sizes of the children surveyed. So, for example, if your sweetie is in the 75th percentile for weight, 75 percent of other little girls her age weigh less than she does. Don’t be concerned if your baby is above or below average — a healthy baby can come in any size, no matter whether that’s in the 90th or 10th percentile.
What doctors are looking for
After your baby’s measurements are taken, the nurse or doctor will plot them out on the chart (or plug them into a computer) to find your pumpkin’s percentiles. Then your pediatrician will compare those with your baby’s numbers from past visits using a growth curve.
While these percentiles can seem scary if they’ve changed significantly from the last checkup (your child’s weight jumped from the 25th percentile to the 90th, for example), don’t panic. Big changes can sometimes be a red flag, but doctors take many factors into consideration when evaluating your child’s health — such as whether your baby’s hitting developmental milestones, the results of the physical exam, genetics, and growth spurts.
To learn more about each type of growth chart — weight, length, and head circumference — keep clicking through.