Someone has to be the shortest in the class. But should you worry if it is your own child? It is a common reason for children to be referred to paediatricians. The medical definition of short stature is height that is two standard deviations below the mean height for age and sex – so the child will be below the third centile on the growth chart. For every 100 children of that age, three would expect to be shorter and 97 to be taller. But there is nothing wrong with being below the third centile if your child continues to grow parallel to the line and doesn't move downwards. A review in the Archives of Disease in Childhood this month estimates that only one in five children below this line will have a medical reason for being short.

So should you check it out, or will it just make your child self-conscious?

The solution

Children under two years of age can move up and down centiles as they do what is called catch-up or catch-down growth to reach their genetically determined growth centile. Around 80% of height is down to genetics. To estimate a child's predicted final height, your doctor would take the mid-parental height. For boys, that is the father's height in centimetres plus (the mother's height plus 14) divided by two, and for girls it is (the father's height minus 14) plus the mother's height divided by two. If a child's projected height lies within 5cm of this range and their rate of growth is normal, then they will be as tall as you would expect from their genetics.

Some children are just late bloomers (called constitutional growth delay) – an x-ray of their bones (left hand and wrist, and comparing it with other children of their age) will show a delay in development, and they may be late starting puberty. They often continue growing when other children have stopped, and grow as tall as you would expect from other family members. Assessing children's height can take months of tracking measurements – growth naturally accelerates in spring and summer.

But, rarely, there are medical reasons for a child being short. This is more likely to be the case if your child's growth slows and moves down the centile chart, or if they have difficulties eating, or have developmental delay, diarrhoea or breathlessness. Essentially, if you have any reason to be worried about your child's growth you should see your doctor. The best known cause is growth hormone deficiency, which can be treated, but there are others, including some genetic syndromes. Most children, if they feel and look well and have a predicted height within their parent's range, will grow as nature intended. Until they get there, research suggests that it is best for the psychological wellbeing of the child not to treat them as younger than they are and not to tease them.