Clare i am so sorry to hear that you are going through this.
Sadly the cut off is 1:300 i was just below that and was classed as high risk my figure from the 12wks scan was 1:294.

I thought the same feelings as you are so please don't be upset by feeling this way. I thought we could get through the pregnancy with not knowing and just wait but after i got passed 15wks i couldn't cope anymore so i ended up with having a amniocentisis done which after a two week wait for the result everything come back clear.

I think if you have the CVS done you can ask for the "FISH" test results that way you will have some idea within 24-48hrs but that is not 100% you have to wait till the results come in. I think that takes two weeks as well.

I really think your odds are really good.
You have to also think what you will do with the results if your baby is born with DS.

If you want to talk please email me michelle@antique-locks.com