Hi Sarah,
If I were you I wouldn't worry about it - I'm not sure how much you can tell from these test results!! A friend of mine had the test done with her second baby - and her result came back as 1 in 4210... and then the baby was born with Down's syndrome, and with half a heart missing, and sadly passed away at the age of only 4. She then had it done again with her next pregnancy, and the result came back as 1 in 10... and her son is absolutely fine!! As she said, she guesses she was just 'that 1'!
We chose not to have any of the tests done, and then had our own little surprise package - George, who was born 3 weeks early and later diagnosed with Down's syndrome. Not picked up on any scans, but fortunately he's managed to avoid the major health problems, and is doing amazingly well. And we wouldn't change him for the world!
At least the amnio will give you a definite answer, and I think they usually do them if your result is less than 1 in 250.
Mrs S x