A friend of mine recently had a baby boy who has been diagnosed with Down's syndrome. I thought I would try to find out a bit about it for her and to maybe get the input of other parents who have children with this condition.

What I found out is that Down's syndrome is a genetic condition known as trisomy, where a person inherits an extra copy of one chromosome. People with the syndrome have three copies of chromosome 21 rather than two.

This additional genetic material alters the finely balanced make up of the body and results in characteristic physical and intellectual features.

Apparently none knows why this abnormality occurs, but it does affect around one in 1,000 babies born in the UK - about 750 babies a year - and is the most common cause of learning disability.

I have heard that there are different types of Down's syndrome, does anyone know what those are?

Yes, there are three different types of Down's syndrome:

The first is Regular trisomy 21 - all the cells have an extra chromosome 21. About 94 per cent of people with Down's syndrome have this type.

Translocation - in this type, the extra chromosome 21 material is attached to another chromosome and one of the parents may carry the translocated chromosome without any signs of the condition themselves. This accounts for about 4 per cent of cases.

Mosaic - in this type of Down's syndrome, only some of the cells have an extra chromosome 21. Around two per cent of people with Down's have this type, which tends to result in milder features than the ones that we most commonly associate with the condition.

There's no cure or treatment for Down's syndrome but treatment of any accompanying health problems and support for learning difficulties allows many people with the syndrome to lead relatively normal and semi-independent lives. Others, however will need full-time care depending on the severity of their condition.

Many people with the condition live well into adulthood, with an average life expectancy of around 60 years.
Physiotherapy, speech therapy and special educational programmes have an important role to play, while specific medical conditions associated with the syndrome are treated as appropriate.

I saw a film recently in which a Down's syndrome sufferer took the lead role! Gone are the days when people with this condition were pushed into the background, advances have meant that many lead very full and productive lives!

I think it is widely accepted that older mothers run more of a risk of having a Down's syndrome baby, so I looked up some data on that. Apparently the likelihood of having a baby born with Down's syndrome at various ages is:
20 years - 1 in 1,500
25 years - 1 in 1,300
30 years - 1 in 900
35 years - 1 in 350
40 years - 1 in 100
45 years - 1 in 30
The site were I found these figures does say that they are approximate figures and that the calculated maternal age is taken by convention to refer to age at estimated or actual delivery of the baby. Also note that the many are lost early in the pregnancy through spontaneous miscarriage.

As to who is likely to be affected, as you can see, the chance of having a baby with Down's syndrome increases with the age of the mother, especially over the age of 35. But as the majority of women have their children when they're in one of the younger age brackets, most Down's babies are born to younger parents.

I understand that in a family who already have a child with Down's syndrome having another child with the syndrome is more likely and if a close family member has had an affected child the odds are also higher. But most cases are random and the risk of recurrence in further pregnancies is very small.
Down's syndrome does not occur along any ethnic lines, affecting people from all ethnic groups and cultures.

It is not possible to prevent the genetic abnormality that causes Down's syndrome, but it has become possible, with greater accuracy to identify, during pregnancy, those babies most at risk.

The most effective and safe method of antenatal screening for Down's syndrome is known as the 'combined' or 'triple' test, which is carried out after about week ten or 11 of the pregnancy and before week 14. This test combines information from ultrasound scanning of the baby along with the results of blood tests which measure certain chemicals in the mother's blood.
This test is routinely offered in most antenatal clinics although in some situations a more limited test may be on offer. These results are then combined with the woman's age at her expected date of delivery in order to give an estimated risk of the baby being affected with Down's syndrome.