What are growth charts?
At each checkup, the doctor or nurse measures your baby's length, weight, and head circumference, and then marks those numbers on a chart of normal ranges for babies of the same age and sex. In the end, you'll find out what percentile your child is in. (The most recent charts take into account both breastfed and formula-fed babies.)
Growth charts show the full range of a child's growth at a specific age. For instance, a length chart for a 2-month-old girl shows the range from shortest to longest. If your 2-month-old daughter is in the 50th percentile, that means she falls right in the middle and is average length for her age.
If your baby was born prematurely, the doctor takes that into account by using gestational age to plot her numbers on the chart. For example, if your baby was born 4 weeks early, her numbers are compared with full-term babies who are 4 weeks younger than her.
Parents sometimes worry needlessly about these percentages. Percentile ratings in a growth chart aren't like grades in school. A lower percentile rating doesn't mean there is anything wrong with your child.
Let's say both parents are shorter than average and their child grows up to be relatively short, too. It would be perfectly normal for that child to consistently rank in the 10th percentile for height as she grows up.
Percentile measurements are a general guide to help you and your doctor assess your baby's growth. What's important is that your baby's growth is progressing.
Remember that your child is an individual and develops at her own pace. There's a wide range of healthy shapes and sizes among children. Genetics, how active your baby is, health problems, and nutrition are just some of the factors that can influence growth.
What are doctors looking for?
Your child follows a particular growth curve and your doctor checks to make sure he stays on that curve. Your practitioner makes sure your baby is gaining weight appropriately (no big dips, for example), and keeps an eye on his weight to make sure it isn't excessive for his length. (That might indicate potential weight problems down the road.)
Instead of singling out one percentile number, your baby's doctor looks at these measurements together to see an overall growth pattern. Sometimes natural growth spurts or slow-downs can make the numbers vary a bit, but usually your child will be in roughly the same percentile for length and weight as he grows.
A few different growth patterns can signal a problem. For instance, if your baby is in the 10th percentile for length and the 90th percentile for weight, his weight could be an issue. It means that he's longer (or taller) than 10 percent of the babies his age, but he weighs more than 90 percent of them. He may go through a growth spurt that puts him back at an appropriate length-to-weight ratio, or his doctor may want to look into why his weight is a little high.
Likewise, if your baby has consistently registered around the 60th percentile for weight at all of his checkups and then his next checkup finds him in the 30th percentile for weight, your doctor will probably want to see if there's a reason he's not growing at the same pace he was before.
Doctors typically use different growth charts, depending on your child's age. The Centers for Disease Control and Prevention (CDC) suggests that doctors use the World Health Organization's charts for the first two years of your baby's life to get the latest and most accurate information.
Once your child turns 2, your doctor will probably use the CDC's growth charts.
All of the charts show length (or height) in both inches and centimeters, and weight in both pounds and kilograms.
How does the doctor take my baby's measurements?
Because an inch or a pound can make a pretty significant difference in where your baby falls on the charts, your child is measured very carefully. It can be tricky to get reliable and accurate numbers – especially if your baby is very squirmy! – but most doctors and nurses are experienced at it.
The doctor or nurse takes three measurements:
After you undress your baby completely – that's right, no diaper – the doctor or nurse places her on a scale (either a traditional beam scale or an electronic model). Weight is measured in pounds to the closest ounce or in kilograms to the nearest tenth of a kilo.
While your child is lying down, the doctor or nurse measures her from the top of her head to the bottom of her heel. Some doctors use a special device with a headboard and a movable footboard for more accurate results.
To measure your baby's head, the doctor or nurse places a flexible measuring tape where your baby's head has the largest circumference – just above the eyebrows and ears, and around the back of the head where it slopes up prominently from the neck.
Why does the size of your baby's head matter? Because the size of her skull reflects the growth of her brain.
So if a baby's brain isn't growing and developing normally, her head circumference may not be increasing as it should. On the other hand, if the skull grows too quickly, it could be a sign of a problem like hydrocephalus (the buildup of fluid in the brain). Both conditions are unlikely, but important to rule out.
By the way, babies' heads are disproportionately large compared to adults' heads, so don't worry if your baby's head looks big to you. Consider your own proportions, too: If you or your partner has a large or small head, your baby might, too.
Can I track my baby's growth at home?
Yes, though doing it yourself may not be as accurate as when the doctor or nurse does it. However, sometimes parents pick up on mistakes made at the doctor's office or catch growth problems sooner. If you want to give it a try:
- Weigh your baby. If you don't have a baby scale, any accurate scale will do. Simply hold your baby and get on the scale. Write down that number. Then put your baby down and get on the scale alone. Subtract that number from your combined weight to get your baby's approximate weight.
- Measure your baby's length. Lay him down and stretch a measuring tape from the top of his head to the bottom of his heel. It's easiest if you have someone help because you'll need to gently stretch your baby's leg straight to do this. Your number probably won't be exactly the same as the doctor's, but you'll get a ballpark figure.
- Measure the circumference of your baby's head. Wrap a flexible measuring tape around his head just above his eyebrows and ears, and around the back where his head slopes up prominently from his neck. The goal is to measure his head at the spot where it has the largest circumference.
Once you have these measurements, plug them into our growth percentile calculator to find out roughly how your baby compares with other babies the same age.
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