Daisy - on the pg threads there are loads of people who didn't see a heartbeat at 6 weeks, but went back a couple of weeks later, and it was fine. I think the main thing is it's the right size, but if you have the chance to go back in a few weeks, then at least that should put your mind at ease - we all know how easy it is to worry.
Rainrain - I hope your scan goes well. I guess to make a decision on paying for an NT test the important thing is to think about what you would do if you were told you had a high risk. The scan has a better detection rate than just a blood test, but would you go on to have cvs/amnio? Also depends if you can afford it - round here I think the NT scan costs about £160, though we get it on the NHS. With dd, the scan was on the last day they can do it, but she was too big for their computer prog to work out the chance, so I had a blood test at 16 weeks, but knew I wouldn't risk mc to have an invasive test even if high risk, as I couldn't imagine terminating the pg for Downs. But other people really want to know for sure.
Sorry - long rambling, hope it makes sense
I had my dating/NT scan today and everything was fine . It now measures exactly right for my dates (was put at 3 days less pg at my 7 week scan), it lay on its back, bum up, doing some boxing! Also had a little swim, its legs looked like a frog! Everything looked normal, and dd sat as good as gold through it all. Not sure what she made of it, as I haven't talked to her about another baby.
Kate - everything crossed for you tomorrow, really hope it goes well, and maybe you'll feel you can join us on the Sept thread
Ellie - didn't think the classes were meant to make you feel worse! Just concentrate on the end result