Like TC i have a 4yo with down syndrome. We knew basically before she was born that she had a heart defect as well as a very high chance of ds. In fact we were told that if she was born without down syndrome it would be very rare. Dd1's heart defect is very common amongst children with down syndrome. However her heart defect was repaired at 8 weeks old and her heart is now almost as good as new.
We were offered an amnio and chose not to have one. We were not concerned with the down syndrome. Dd1's cardiac surgery was carried out at the Royal Brompton - only cause that is the hospital that our local hospital worked with iyswim.
Her heart defect was detected at the 20 week scan and we were then referred to the Harris Birthright Trust where a fetal cardiologist gave us a fetal cardiac scan and a correct diagnosis.
The info that Geekgrrl has given you the link for is good info. I decided against an amnio simply because we had decided we would have the baby and did not therefore see the need for the amnio.
With dd2 - again i was given a higher than normal risk for down syndrome as they found echogenic focii in her heart. Again we refused an amnio - nothing anyone could tell us about down syndrome - it was our reality. I do know that other people in my position would have the amnio as they needed to know but for us - again she was our babe and we would not be doing anything about it.
I am now pregnant a 3rd time and whilst dh wants me to have a nuchal fold test ( am now turning 38) I am quite happy not to have one and know no matter what the risk comes back we will not be having any further testing apart from the 20 week scan.
Most heart defects that children with ds have are very common and whilst serious are still repairable. The one my dd1 has basically means she has no central wall in her heart to divide her four chambers as well as the av valve being dodgy. They simply put two patches in her tiny heart and repaired the valve. As she ages and grows the heart will grow around the patch. In terms of future surgery - she may need further repair to the av valve but that would be as a teenager if at all.
Sorry for the long post but I just wanted to share my story with you.
I would strongly recommend contacting the DSA UK - even just for someone to talk with. Dh found that really helpful.
Anything you want to ask - feel free. If you want to email me - edwali at excite dot com.
My dd1 is a very delightful, cheeky amazing girl who attends a mainstream kindy as well as a kindy for children with sn and delights all who come in contact with her. She is a big sister who adores her little sister. Since we moved to Aus she has come on in leaps and bounds.