By Dr. Catherine Gant

Growth charts are used to compare a child’s growth (typically height, weight and head circumference) with the normal for his or her age. When your baby is born you are given a booklet with these charts in and growth will be plotted every time you see your health visitor or midwife.

ABOUT GROWTH CHARTS

PERCENTILE LINES

Growth charts show a range of normality for any given population.

The middle line on the chart is called the 50^th percentile and shows the average for that age.

In a normal population half the children (50%) will lie above this line, and half below. The upper and lower lines are usually the 10^th and 90^th percentiles so in a normal population, 20% of children will fall outside this normal range.

Doctors often use charts with 3^rd and 97^th centiles. 3% of normal children fall below the 3^rd percentile and 3% of normal children fall above the 97^th percentile, so children in either of these positions may be completely normal.

Race

There are different charts for different ethnic groups and the charts vary even between adjacent European countries.

Familial Factors

Different growth patterns run in families and should be taken into consideration when considering charts; if the parents were both tall and skinny as children the children may be the same.

Parental Height

As a very rough guide to calculate potential adult height:

For girls – take 4 inches or 10 centimetres off the father’s height and take the average of this height and the mothers height. The girl’s final height will usually fall within a range 3 inches either side of this height.

For boys – add 4 inches to mother’s height and average this height with the father’s height. The boy’s final height will usually fall within a range of 3 inches either side of this height.

Age of Puberty

Children grow steadily throughout childhood and when they reach puberty they have a growth spurt.

After the growth spurt the growth points in the bones (epiphyses) fuse and they stop growing.

So, children who go through early puberty may appear taller than their peers during their early growth spurt but will stop growing earlier and may end up shorter. Children who have a later puberty grow at the steady rate for longer and so start their growth spurt taller and may end up taller. The percentile that your child is on during childhood may not reflect their adult height. The age of puberty does have a familial component, so if both parents had early puberty the child may as well and vice versa.

Comparing Height and Weight

As a general rule, the weight is normal if the percentile is within 40% of the height percentile. For example, if the height is on the 50^th percentile the weight can lie quite normally between the 10^th and 90^th percentile for that age.

If you want a rough idea of the normal weight for your child’s height measure their height and see what age this corresponds to on the 50^th centile. This is their height age.

On the weight chart find the 90^th and 10th percentile weights for that age.

This gives you an approximate normal range of weight for that height.

Measuring Length

Children are measured lying down until the age of two and standing after this. This shows on the charts as a small drop in height at age two years. Length measurements are extremely variable depending on who performs them, particularly in babies and should be taken by someone experienced in this area.

Prematurity

If your baby was more than a week early the hospital might have plotted this on the chart. For example, if a baby is four weeks early the birth weight would be plotted four weeks to the left of the birth line and their weight at four weeks will fall on the birth line. Subsequent measurements should also be plotted to take account of this shift or the charts will be meaningless.

CONCERNS

These are general guides only. If you are worried about your child’s growth or nutrition please contact your doctor or health visitor. A slowing of growth can be the first sign of a serious disease, such as hypothyroidism or malabsorption.

DOWNLOADING CHARTS

Normal charts of height and weight can be found at United States Growth Charts. Click on new charts. These are similar to British charts.

 Growth Charts for Children with Down's Syndrome (The Archives for Disease in Childhood featured growth charts for children with Down's syndrome in its August 2002 issue. You need to subscribe to see them.)

Growth Charts for Chinese children

Growth Charts for Indian and Inuit Children in the USA

You can order a personalised chart for your child at Personal Growth Charts