I have a 3 1/2 year old with Down Syndrome
\link{http://www.mumsnet.com/Talk?topicid=1700&threadid=154612&stamp=060313093017\seen here}
When I was pregnant with dd1 - they discovered a hard marker for Down Syndrome. She had a heart defect that they detected at 22 weeks pregnant. Orignally the local hospital had told us they thought it was a different heart defect with a more serious prognosis. We discussed what we would do after we had the fetal cardiac scan. For dh and I we were having this babe and we would just take it each day at a time. WHen we were told the correct heart defect that she had we were told that it would be very unusual for her to be born without Down Syndrome. She has a heart defect very common to children with Down Syndrome.
The fetal cardiac scan was done at Harris Birthright trust and we were offered an amnio to find out for sure. We had already decided that our daughter would be born and so decided against the amnio simply as it would not make a difference to the outcome.
I think that is where you need to start.... no doubt you are imagining all sorts of things regarding having a child with Down Syndrome. For me - as we were keeping the babe and really weren't scared of what we could face - we knew families who had and were raising children with down syndrome - there was no point putting myself through an amnio.
Others who have been in my position or similar have gone on to have amnios simply because they were unsure what to do or wanted to know for sure or knew without a doubt that they would terminate the pregnancy.
When pregnant with dd2 - they discovered a soft marker in the heart for dd2. This increased my risk further of having another child with down syndrome. We again declined am amnio - again because it would not change the outcome and we did not need to know - we knew what it was like to raise a child with Down Syndrome. In fact to be honest I was terrified of raising a child without special needs - I did not know where to start. Dd2 was not born with Down Syndrome.
Sure there have been tough time - worst was seeing my daughter go through two open heart surgeries within three days when she was 8 weeks old, almost losing her at 8 weeks old. I can't imagine not having her in my life.
Sorry this is so long - just wanted to share my story with you. I second Yafta's advice in essence but wanted to share with you a little more than that.