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What Influences Your Baby’s Growth?

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WebMD Feature
Reviewed by Louise Chang, MD

A baby's first year is a time of incredible growth. In just the first six months of life, babies will double their birth weight. By the end of their first year, they'll triple their weight.

Most babies have their first well-baby visit within the first couple of weeks after they are born. Then they'll see the pediatrician again at two, four, six, nine, and 12 months. During these visits, the doctor will check the baby's growth. The baby's measurements will be plotted on a growth chart and tracked over time.

Growth Charts: What Do They Mean?

Most doctors use the growth charts established by the CDC. The CDC developed these charts by collecting measurements from thousands of American babies and children over time. Growth charts track three different measurements of baby growth: height, weight, and head circumference.

Growth charts make it easy for pediatricians to track a baby's development. "Babies come in all different sizes," says Joanne Cox, MD, associate chief of General Pediatrics at Children's Hospital Boston. "Growth charts allow you to evaluate in a very quick and easy way whether a baby is growing normally."

Here's how growth charts work: Doctors plot the baby's measurements on the chart to get a percentile. The percentile shows how the baby is growing compared to other babies of the same age and gender. For example, if a six-month-old girl is in the 25th weight percentile, it means that 25% of girls her age weigh the same or less than she does and 75% of girls her age weigh more.

Percentiles are a useful way to follow a baby's growth, but some parents get too caught up in worrying that their child is too high or low on the scale. Remember that growth charts are just a comparison -- they're not grades.

"It's not like you get an A+ if you're in the 100th percentile. It simply means this is where your child is compared to peers his own age," says Ari Brown, MD, FAAP, a pediatrician in Austin, Texas, and co-author of Baby 411 and Expecting 411."Really what we're most interested in is not the percentiles, but how your child is tracking to make sure that he's following his curve."

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.

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