A growth chart is a graphical representation of how a child grows over time. The chart is based on data from the World Health Organization (WHO) and shows the average height and weight of boys and girls of different ages. Growth charts are useful for tracking your child's development and growth over time.

Components of a Growth Chart

You can think of a growth chart as a graph with an x-axis and a y-axis. Usually, the x-axis represents the age in either years or months. The y-axis changes with the required reference. The reference can be the height in centimetres or inches, weight in kilograms, or body mass index in kg/m2.

How To Read A Growth Chart

Most often, the x-axis of the growth chart is divided into twelve equal portions to represent each month of the year. In some countries, like the United Kingdom, which uses decimal ages, each year is divided into 10 parts accordingly. Indian charts use the 12-month division.

Standard Growth Charts

These growth charts show the standard percentile lines for height and weight. Percentile represents the percentage of people who belong to a particular range of a parameter. The parameter could be height, weight, or head circumference.

To illustrate percentiles, let us take an example. Say a child's height is at the 75th percentile. This means that in a group of similar-aged children, the child is taller than 75 and shorter than 25.

Percentile Lines

In a standard growth chart, you will find seven percentile lines. These would be the 3rd, 10th, 25th, 50th, 75th, and 97th percentiles. These are the standard percentiles for height and weight. An individual in the 3rd to 97th percentile would be in the normal range. But below the 3rd and above the 97th percentile range, a score is regarded as outside the normal range.

While the cut-offs for overweight and obesity are the 85th and 95th percentile lines in the BMI charts, In proportion charts, another type of score called the Z score is used instead of percentile lines. A difference above 2Z in the upper and lower segments is out of the normal range.

It doesn’t matter whether your child measures at a low or high percentile. It only matters that your child is following the curved lines, which indicates that he's growing healthily over time.

How to Figure out the Growth Percentile

To locate your child's growth percentile, first, find your child's age on the x-axis. From here, draw a straight line up. Then find your child's measure (say, height) on the y-axis. Draw a straight horizontal line towards the vertical line. Mark the point where the two lines intersect. Locate the curve that's the closest to this point. Follow the curve line up. Continue until the very end. The number you find at the end of the line is the height percentile rank of your child.

It doesn’t matter whether your child measures at a low or high percentile. It only matters that your child is following the curved lines, which indicates that he's growing healthily over time. If your child's growth percentile crosses the normal range, then consult a doctor.

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1. Which growth chart is best?

CDC recommends the WHO growth charts to keep track of growth for infants and children ages 0 to 2 and CDC growth charts to track the growth of children older than 2.

2. Why do paediatricians use growth charts?

Growth charts help track the growth of your child. By ensuring that the child's growth pattern confirms the curve in a growth chart, you can look out for any deviations.

3. How do you read a growth chart?

Locate your child's age and measurement, like the weight on the growth chart. Find the curve closest to the intersection point and follow the curve upward to the end of the line to find the percentile line in which your child falls.

4. When should I worry about my child's growth?

You should talk to a doctor if your child's growth percentile is below 3 or above 97 (for height and weight) or if a certain growth chart says you should.

5. What are the disadvantages of a growth chart?

The problem with growth charts is that they might label underweight a lot of children who seem to be healthy and live in developing countries like India.