FWIW there are lots of women on BB who have been told they are certain bubs has something wrong, only to birth perfectly healthy and wonderful children. The NT scan results are no where near accurate in so many cases.
The NT scan and blood tests are not diagnostic tests, they are screening tests. They do not claim to indicate with certainty that 'bubs has something wrong'. The result is a calculated value that predicts the likelihood of the baby having T21 or T18/T13 which can help determine which women should be offered further diagnostic testing. So, its not that these tests are inaccurate- they are accurate at what they do. If you want a definitive answer then you have CVS or amnio.