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Growth Charts: What Do They Mean? continued...

If your baby stays in the 15th percentile for both weight and height, it doesn't necessarily mean there's anything wrong. Your baby just might be smaller than other children of the same age.

Doctors start to investigate if a baby's height and weight measurements don't match up. For example, if the baby's weight is in the 50th percentile but his height is only in the 20th percentile, or his weight suddenly drops two or more percentile points, there could be a growth problem.

Getting a Head of the Curve

Plotting height and weight measurements on the growth chart helps your doctor determine whether your baby is growing normally and getting enough nutrition. Measuring head circumference shows the rate of head growth, which can be an indicator of brain development.

"If the baby's head isn't growing fast enough, then you worry that there was some kind of injury to the brain during birth, or the baby was born with some abnormality," Cox says. A small head could also be a sign that the bones of the skull have closed too early, leaving less room for the brain to grow.

When the head circumference is tracking larger than average, it could be due to fluid on the brain (hydrocephalus). Or, it could just mean that your baby has a large head. "Often, we'll measure the parents' head, because kids with large heads often have parents with large heads," Cox says.

More important than the size of a baby's head is how fast it’s growing. If the baby's head is getting larger than normal, the doctor might do an ultrasound to find out the cause of growth.

Plotting Preemie Growth

A premature baby isn't going to follow the same growth curve as a baby who was born full-term. Pediatricians will track a premature baby differently, or by using a special premature growth chart.

Preemies might start small, but eventually they catch up with their peers. "The first parameter that catches up is the head, and then the weight and height fall in after that, Brown says."

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