Information about average height for children comes from growth charts. Doctors use growth charts to determine how a child's height and weight compares to her peers, and to track her growth over time. They provide information about average height, weight, head circumference and body mass index, or BMI, for boys and girls, up to age 20.
History
The National Center for Health Statistics, or NCHS, developed the first growth charts in 1977 as a way for health professionals to determine if a child was growing at a sufficient rate. In 2000, the Centers for Disease Control and Prevention, or CDC, revised the growth charts using more data, especially for infants, and added BMI charts to help determine if a child is overweight or obese.
Chart Features
There are separate growth charts for boys and girls due to natural differences in size and development. The height table gives average height values monthly, for the third to 97th percentile, in metric units, or cm. There are two sets of charts, one for infants, ages 0 to 36 months, and one for children and adolescents, up to age 20.
Percentiles
According to the CDC, percentiles are the most commonly used measure to judge the growth of children in the United States. Percentiles allow comparison of a child's height to his peers. They rank his height against his boys his age, indicating what percentage of children he is the same or taller than. For example, a 7 year old in the 75th percentile of height is the same height or taller than 75 percent of 7 year old boys and shorter than 25 percent of them.
Misconceptions
According to Kids Health, usually there is no ideal percentile with respect to height. The Canadian Paediatric Society does suggest that children below the 3rd percentile in height may be short because her parents are short, or due to long-term malnutrition, delayed maturation, chronic illness, or a genetic disorder. For the most part, a sudden change in a child's growth pattern, going from the 60th percentile to the 30th percentile in a year, for example, could signal a growth problem. Yet it is important to keep in mind that many children do change percentiles during development, especially during infancy and puberty.
Considerations
These growth charts were not formed using data from exclusively breast-fed babies, and whether an infant is breast-fed or formula-fed can affect her growth. According to the CDC, exclusively breast-fed infants gain weight more quickly in the first two to three months, but then tend to weigh less than formula-fed infants from six to 12 months. These charts also do not include data on very low birth weight infants and these infants will most likely fall in low percentiles on this chart. As an alternative, the Infant Health and Development Program, or IHDP, provides information for infants of a very low birth weight.
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