The following questions and answers are copied from the Downs Syndrome Association and explain what Down's Syndrome is and how people with this condition are affected.

What is Down’s Syndrome?

Down’s syndrome is a genetic condition (i.e. something you are born with, which is present in the baby from the moment of conception) caused by the presence of an extra chromosome. Chromosomes are tiny particles, which are present in every cell in every tissue in our bodies. They carry the ‘blueprint’ for all the characteristics we inherit. This blueprint is carried in the form of a coded message in a chemical substance called DNA. There are 23 pairs of chromosomes in each cell, hence 46 altogether. One of each pair comes from the father, one from the mother.

In 1959, a French geneticist, Professor Jerome Lejeune, discovered that Down’s syndrome was caused by the presence of an extra copy of chromosome 21, making 47 chromosomes in all.

A ‘syndrome’ is a collection of signs or characteristics. The name ‘Down’ comes from the English doctor, John Langdon Down, who first described the syndrome in 1866, nearly 100 years before the extra chromosome was discovered. Everyday in the UK, between one and two babies are born with Down’s syndrome, which means that one baby in 1000 has the condition.

People with Down’s syndrome all have a certain degree of learning disability (mental handicap). The degree of disability varies from person to person and it is impossible to tell at birth what that degree will be.

What causes Down’s syndrome?

As yet, we do not know what causes the presence of extra number 21 chromosome. It can come from either the mother or the father. The most common type of Down’s syndrome, Standard Trisomy 21 (also known as Primary Trisomy 21 or Regular Trisomy 21), occurs because of an unusual cell division which has produced either an egg or a sperm with 24 chromosomes instead of 23. When this egg or sperm fuses with an ordinary egg or sperm, the first cell of the developing baby has 47 chromosomes instead of 46, and all that baby’s cells will have 47 chromosomes. There is no way of predicting whether a person is more or less likely to make eggs or sperm with 24 chromosomes. We know that babies born to older mothers have a higher chance of having Down’s syndrome, but we do not know why.

Could we have prevented our baby having Down’s syndrome?

It is important to remember that you are not to blame for your baby having Down’s syndrome. Nothing you did before or during pregnancy has caused it. It occurs in all races, in all social classes and in all countries throughout the world. It can happen to anyone.

Does it mean that any further children we might have will also have Down’s syndrome?

Standard Trisomy 21 is not hereditary. However, once you have had one baby with Down’s syndrome your chances of having another child with the condition are increased. Overall this chance is between 1 in 100 and 1 in 200, which is considerably less than the chance of, say, having twins ‘out of the blue’. When thinking about your next pregnancy it would be helpful to talk to a genetic counsellor who could talk things through with you in some detail.

What does the extra chromosome mean for our baby?

All people with Down’s syndrome share some certain physical characteristics, though not every child with the condition has every characteristic. Your baby will have inherited physical characteristics from both of you, just like any other of your children, as well as sharing some of the common signs of Down’s syndrome. Your baby is unique. Some parents wonder if there is a link between the number of these physical characteristics and the future development of their new baby. In fact, there is no way at this early stage of predicting the level of ability of your child.

The extra chromosome means that your baby will be slower to reach her milestones and will have a certain degree of learning difficulty, but most children with Down’s syndrome do learn to walk and talk, ride a bike and read and write, in fact to do most of the things other children do. It’s just that their development is usually delayed.

What are the common signs of Down’s syndrome?

Your baby may have looser muscles and joints than other babies. This will improve as she gets older.

She may have lower than average birth weight and put on weight at a slower pace than other babies. (Special weight charts are available for babies and children with Down’s syndrome from the National Office of the Association).

Babies with Down’s syndrome often have eyes that slant upward and outward. Their eyelids often have an extra fold of skin (epicanthic fold) which appears to exaggerate the slant. This does not mean that there is anything wrong with the eyes. They just look different.

The back of your babies’ head may be flatter than average.

Many babies with Down’s syndrome have a single crease which runs right across the palm of the hand. Doctors often look for this characteristic crease, as a sign that a baby may have Down’s syndrome. However, some babies who do not have Down’s syndrome also have a crease like this.

All babies are different from each other and the same is true of babies with Down’s syndrome. This means that in some babies the characteristic signs of Down’s syndrome are fairly easy to recognise soon after birth, whilst others may look and behave little differently from other babies. However, experienced doctors and midwives are usually very good at picking up subtle differences, which suggest that a blood test should be done to check the chromosomes.