Nefertiti - I am 37 and so I had a fairly high risk to start off with purely due to age (1:160) but after the scan it was reduced to an adjusted risk of 1:2327 which made me a low risk for chromosmal abnormality. I was 12 weeks and 6 days when I had the scan.
I thought a lot about what I would do if there was an abnormality and obviously my decision would have been based on the degree of severity of abnormality and survivability post birth. Also, I have horrible pregnancies so it would have had to have been something serious for me to terminate as I don't think I could go through another first trimester again!

I just wanted to know cause, as you say, I would prefer to be prepared than find out at the birth. (which still could happen I guess).
Good luck and I know it's hard not to stress, cos I couldn't help it either, but try not to worry!