Growth refers to an increase in size. This is easy to gauge by measuring your baby’s length, weight and head circumference.
Normal growth in healthy babies is obvious as they grow out of their clothes and suddenly become too large for a bassinet or baby bath or other item that seemed enormous when they were just a newborn.
Percentile charts are based on measurements of babies and children from a certain population (for example, all the Australian babies in a certain year). The Victorian government percentile charts have been updated recently using data drawn from between 1963 and 1994. These charts, along with many other percentile charts used in Australia, are based on United States surveys.
As normal variations in height and weight are considerable, the percentile charts are drawn to allow for the variations. If you look at percentile charts you will see that the lines represent the 5th, 10th, 25th, 75th, 90th and 97th percentiles for weight, height and head circumference.
Length is measured when the baby is lying down. Height is only measured for children over two years of age when the child is standing. Most babies’ weight and length fall somewhere between the 5th and 97th percentile, although certain populations (e.g. people of Asian origin, people with specific disabilities such as Down syndrome) may fall outside the ‘normal’ range.
If a baby is on the 5th percentile for height and weight it means that 95% of babies are taller and heavier than he is. And a baby on the 90th percentile for height and weight, is taller and heavier than 90% of other babies. In both examples, the baby, although very different in size and at different ends of the percentile range, is within the normal range.
Head circumferences can also be charted on the percentile chart. A baby’s head grows rapidly in the first year making it easy to check that it is growing at the right rate.
WHO Child Growth Standards
In April 2006, the World Health Organization (WHO) released the WHO Child Growth Standards. These new standards are based on a survey of children from Brazil, Ghana, India, Norway, Oman and the United States. Similar to percentile charts, the WHO standards use Z-scores to show the spread of growth data for children of the same age.