Growth charts are the most commonly used tool in a doctor's office to assess the size and growth patterns of children. The growth charts use percentiles to mark where children are, this allows them to be compared to other children who are the same age. The percentiles are used to rank the position of each child because they indicate what percent of the reference population the child would equal or exceed. For example, if your child is in the 50th percentile for weight at the age of 3 years old that means that they weigh the same or more than 50% of 3 year olds, but she also weighs less than 50% of the 3 year olds in the reference population.

Because of how important growth charts are for monitoring your child's growth, many parents have begun using them at home. One of the ways that you can get a growth chart to use at home is to ask your doctor's office for a copy, but you can also find a number of growth charts available for you to download online. Many parents find growth charts hard to use because of how confusing they are, and the reason that they are so confusing is because a lot of information is being compacted into a small space.

The CDC is the department that collects the data to be used in the growth charts and they are the department responsible for maintaining and updating the growth charts, as needed. The growth charts were last updated in 2000. The data that is collected for the growth charts is the physical measurements of length or stature, and weight from infants, children, and adolescents up to 20 years old. Head circumference measurements are also collected from infants and children up to 36 months. This data was obtained from a series of national health examination surveys that was conducted by the National Center for Health Statistics, which is a part of the Centers for Disease Control, from 1963 to 1994. The surveys and data sources used included:

• National Health Examination Survey Cycles II and III
• National Health and Nutrition Examination Survey I, II, and III
• U.S. Vital Statistics
• Wisconsin Vital Statistics
• Missouri Vital Statistics
• Fels Longitudinal Study
• Pediatric Nutrition Surveillance System

Here are the steps that you need to follow in order to properly use and read a growth chart.

Step one:
Find the right growth chart. There are different growth charts available for children depending on their age and their sex. Therefore, if you have a girl who is 5 years old you will not want to use a growth chart that is for a boy from birth to 36 months.

Step two:
Find your child's age at the bottom of the growth chart. Draw a vertical line on the growth chart through their age, the line should cover the length of the chart.

Step three:
Weigh your child on an accurate scale, your scale might need to be adjusted or calibrated before you begin using it.

Step four:
Find your child's weight on the right hand side of the chart and draw a horizontal line. When drawing the lines you want to make sure that they are a light colored line that you can erase later or just use an imaginary line. The reason for this is that if you draw actual lines each time you plot your child's age, weight, body mass index, and height it will end up looking rather messy, and can be hard to read.

Step five:
Find where the two lines cross each other. Put a mark on the spot where the lines cross each other. This mark needs to be permanent because it is where your child is currently at on the growth charts.

Step six:
Find the curve that is closest to the mark, follow it up, and to the right until you find the number for your child's percentile.

Other things to keep in mind:

• The same steps can be followed to plot your child's height and body mass index.
• If your child is above the 95th or below the 5th percentile, you will not be able to find an exact percentile. All that you will be able to see is that they are above or below the growth charts.
• There is no perfect percentile for your child because healthy children come in all shapes and sizes. So being in a high or low percentile does not mean that your child is healthier than other children are or has a growth or weight problem. It just means that they are smaller or bigger than average.
• If the spot where your child's age and weight, age and height or age and body mass index comes together does not pass through a curve finding your child's percentile is going to be harder. You would still need to follow all of the above steps but you would have to imagine where the curve is, which makes the percentile a best guess. For example if a 2 year old boy weighed 31 pounds the curve would be somewhere between the 75th and 90th percentiles, which most people would figure is between the 80th and 85th percentile.

• Genetics, gender, nutrition, physical activity, health problems, environment, and hormones can all affect a child's height and weight.
• Growth charts are used to show whether your child is developing proportionately, not just how big or small they are.
• Even if the growth chart shows a change in pattern for your child's growth, this does not mean that there is a problem. The reason for that is that the doctor is going to interpret the growth chart in context of your child's overall well-being, environment, and genetic background. For example, is your child meeting other developmental milestones or are there other signs that your child is not healthy? Was your child born prematurely?
• Girls and boys are measured on different growth charts because they grow in different patterns and grow at different rates. Age is also a factor with growth charts because you grow at different rates during certain ages. In addition, special growth charts are used for children with certain medical conditions, such as Downs Syndrome.
• Head circumference on children up to 3 years old is measured and charted on a growth chart because it can be used to provide clues about brain development. Doctor has looked to see if your child's head is larger or smaller than most other kids are, or if the head stops growing or starts growing quickly, it can signal a problem.
• Children between the ages of 6 and 18 months can move up or down on their percentiles without raising any concerns, but older children should follow the growth curve closely.
• Growth charts can be used for breast-fed babies, but you must consider certain things when looking at the growth pattern. The reason for this is that the manner of feeding can influence an infant's growth. For example, infants that are only breast-fed will rapidly gain weight in the first 2 to 3 months. However, from 6 to 12 months breast-fed infants usually weigh less than formula-fed infants do.

The one thing that you need to remember about growth charts is that the percentiles used in them do not actually indicate how well your child is growing. The purpose of the growth chart is to follow your child's growth over time or you can use it to find a pattern of your child's growth. The reason for this is that a child who is only in the 5th percentile can be growing just as well as a child in the 80th percentile. To figure out how well your child is growing it is important for you to look at your child's growth over time. Your child should be growing at normal rate, no matter where they are on the percentile. To ensure that your child is growing you will want to make sure that they are following their growth curve, meaning they have always been in or around the same percentile on the growth charts. If you have concerns about your child's growth, the most important thing to do is to talk to your child's doctor.

Here are some websites that you can visit to download growth charts for you to use at home. Remember to download the appropriate growth chart for your child based on gender and age.

•     Length and Weight Growth Chart for Boys from Birth to 36 Months - http://pediatrics.about.com/cs/growthcharts2/l/blboysbirth.htm
•     Length and Weight Growth Chart for Girls from Birth to 36 Months - http://pediatrics.about.com/cs/growthcharts2/l/blgirlsbirth.htm
•     Stature and Weight Growth Chart for Boys from 2 to 20 years - http://pediatrics.about.com/cs/growthcharts2/l/blboystwo.htm
•    Stature and Weight Growth Chart for Girls from 2 to 20 years - http://pediatrics.about.com/cs/growthcharts2/l/blgirlstwo.htm
•     Body Mass Index Growth Chart for Boys from 2 to 20 years - http://pediatrics.about.com/cs/growthcharts2/l/blboysbmi.htm
•     Body Mass Index Growth Chart for Girls from 2 to 20 years - http://pediatrics.about.com/cs/growthcharts2/l/blgirlsbmi.htm