Around one in every 1000 babies born in the UK will have Down's syndrome; there are approximately 40,000 people in the UK with the condition.
What is Down's syndrome?
It is a congenital disorder which occurs as a result of usually having an extra copy of chromosome 21.
Children born with this extra chromosome often have impaired cognitive function and physical growth.
A few of the common physical traits are low muscle tone, small stature, an upward slant to the eyes and a single deep crease across the centre of the palm.
The syndrome is named after John Langdon Down who published the first accurate description of children with Down's syndrome.
What causes Down's syndrome?
It is not entirely clear why at the very beginning of some pregnancies the cells produce an extra copy of chromosome 21, we do know that the chance of having a baby with this syndrome increases with age, although it can also happen in pregnancies where the parents are young.
There are actually 3 types of Down's syndrome- Non - Dysjunction - caused by an error in cell division, this accounts for about 95% of all children born with Down's syndrome.
Mosaicism occurs when there are a mixture of two cells some containing only 2 copies of chromosome 21, this happens in 1% of cases.
Translocation which accounts for about 4 % of children when the actual number of chromosomes is still 46 but chromosome 21 attaches to another chromosome - usually chromosome 14.
A 35 year old woman has a 1/350 chance of having a baby with Down's syndrome and this increases to 1/100 by the age of 40.
How common is Down's syndrome?
In the UK there are about 1000 babies born every year with Down's syndrome - in the USA about 6000.
Who can I speak to if I have any questions about Down's syndrome?
Your GP, midwife or obstetrician can help you with questions you may have. The Down's Syndrome Association website is also a great place to find further information.