No problem OZzy - the questions you ask are really valid and as Jac says parly hinge on what you would do with that information.

NT u/s can be an absolute nightmare in the hands of some operators and I have seen professionally women who have been left in a complete state of despair from info received from operators. Thankfully when they sought out a second opinion their fears were allayed. It is my *personal* belief - so please no one shoot me down that NT u/s should only be done by a foetal medicine specialist. This is an obstetritian whose speciality is prenatal testing and diagnosis. It's kind a like you don't go to an auto electrician to balance your wheels - sure he may have some knowledge but he isnt' the expert. When you go to a foetal medicine specialist the doctor is there in the room - he looks at your baby - not just the nuchal fold but other soft markers, he looks at your blood results and he talks to you then and there and gives you your risk factor.
YOu can ask as many questions as you like and you are speaking to "the horses mouth".

There is a terrible fear of trisomy 21 (Down's Syndrome) however the reality is that in the great majority of cases this can be excluded and you will leave with the knowledge that in all probability your baby is perfect. Of course nt u/s doesn't preclude other conditions but a foetal expert looking at your baby has a very astute and trained eye. In Frank's case he has had one case slip through - in all the years of doing nt u/s. To explain this woman had a 1:290 risk of her baby having trisomy 21 - she decided against amniocentesis but her baby indeed was born with trisomy 21. NT u/s isn't fool proof but it gives an extrmemly accurate picture. However, I do believe the accuracy hinges on who does the scan. With a foetal medicine ob with good stats I believe you could feel very comfortable with her/his opinion.

I guess the question on weather to test lies with how you feel. If you believe that you would feel more relaxed if this was done then it's probably a good idea. If you feel that it doesn't matter what the outcome then it's probably not necessary. I have seen women go ahead with pregnancy when there has been definitive diagnosis of abnormality. A large number of these women (though not all) felt glad tht they had pre warning - they kind of did some of their grieving for the baby they thought was coming before it came. So when the baby was born they could welcome her/him with the full knowledge of who she/he was. Do you follow?

I think the whole prenatal testing thing is really difficult. I know personally I find myself very stressed before the nt u/s. However, thankfully each time I have left feeling very relieved!

It's a big decision and I think that you are very wise for considering all angles and not just accepting but asking questions. Good luck with it all - I would love to hear what you decide....