Babies all develop at different rates – and because of that, it’s a good idea to treat percentile chart measurements as a guide. The most important thing is that your baby is healthy, responsive and happy, not how he compares with other babies on a chart.
Growth refers to an increase in size. This is easy to gauge by measuring your baby’s length, weight and head circumference.
You may not even need to use a growth chart – as your baby grows, you may notice him outgrowing his clothes, bassinet or baby bath, or other items that seemed enormous when he was just a newborn.
Growth charts (percentile charts)
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’ll 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 (for example, people of Asian origin or people with specific disabilities, such as Down syndrome) may fall outside the ‘normal’ range.
Understanding the charts
If a baby is on the 5th percentile for height and weight, it means that 95% of babies are taller and heavier than she is. A baby on the 90th percentile for height and weight is taller and heavier than 90% of other babies. In both examples, the baby is within the normal range, even if these are at different ends of the percentile range.
Head circumference 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’s 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.