What an awful experience that must have been for you... I can understand why you would be anxious about getting a misleading NT scan again after having been through what you have.

When we were deciding whether or not to have the NT scan my OB had what I thought was an interesting take on the situation. Basically he suggested that we decide whether or not we would terminate the pregnancy if we did find out that our baby had Down Syndrome before deciding to have the NT scan. If we would terminate, he then said that we should go ahead with the NT scan and any other testing that was necessary to determine it. But if we were of the mind that we would keep the baby he recommended that we not do the NT scan, because then if it indicated a problem you would be risking miscarrying a child you intended to keep with an amnio or CVS.

I'm not necessarily sure that I agree with the logic, but it is an interesting take on what is a terribly difficult decision...

Good luck with it all!