SY,
my oscar results is also borderline but my gynae said that as long as passed, means not high risk. He mentioned to go for the detailed scan too (actually i thought detailed scan is a must). only if something is not right, then go for amino. So don't worry, go for your detail scan first. Take faith that at least you are not considered high risk yet so don't panic too fast.
Mrs Chua: Congrats! happy for you!