What is normal growth?

There is a wide variation in what is considered normal growth in childhood. For example, at two years of age, the normal range is from 33 to 37 inches for boys and 32 to 37 inches for girls; at five years, from 40 to 47 inches for both boys and girls; at 10 years, from 51 to 59 inches for boys and 50 to 59 inches for girls, and at 15 years, from 60 to 72 inches for boys and 59 to 68 inches for girls.

How is growth measured?

Regular, accurate measurements of weight and height are an important part of a child's health care. In infancy, length and weight are regularly checked at visits to the doctor. During early childhood, measurements are usually taken about twice each year, and more frequently if there is anything unusual about a child's growth.

Throughout the child's school years, it is helpful to obtain accurate measurements at least once a year. A variety of devices and equipment can be used to measure height and weight. Doctors and nurses generally use an instrument called a stadiometer to obtain accurate height measurements.

To determine whether your child is growing normally, your doctor will compare your child's growth to that of other children of the same age and sex. Growth charts showing the averages and normal ranges for height, weight, weight-to-height ratio, and head circumference of children at different ages are used to evaluate your child's growth over time.

Height is shown on the vertical edges of the growth chart, and age is shown along the bottom of the chart. The curved lines are called percentiles. These percentile lines represent the data collected from a large group of children in a national survey, expressed in percentages, so they represent the average growth for children across the nation at different ages.

As an example of how to understand these charts, let's say a child's height is at the third percentile – this means that out of 100 children of the same age and gender, 97 are taller and only two are shorter. Children typically grow along a certain percentile line from the toddler years on. If a child begins to move downward away from his or her percentile on the growth chart, this could be cause for concern and requires investigation, no matter how tall he or she is.

Overall, the normal range for height is generally considered to be between about the third and the 97th percentiles. This means that about 94 percent of people (children and adults) are in the normal height range, 3 percent are taller and 3 percent are shorter. It should be noted that the normal height range differs from one country to another. For example, people in the Netherlands tend to be much taller than people in Japan.

A different type of chart, called a height velocity chart, is used to record and evaluate a child's growth rate or how fast a child is growing. The speed of growth is very fast in the first three years of life. But from around three years of age, until about nine or 10 years of age, the speed of growth slows down a little more each year.

Then, at puberty, there is a rapid increase in growth rate – the pubertal growth spurt – during which the speed of growth usually doubles. By regularly measuring height, weight and speed of growth, your child's doctor will be able to determine if your child's growth is following a normal pattern.