How deeply concerned should i be with with my nt screen coming back with a 1:190 chance of the extra chromosome? i am 33 no previous history.

Not a lot : You do not need to worry much. 1/190 chance means 0.5% chance of a trisomy. That's 99.5% chance the baby is normal. You need to understand the purpose of the test. The vast majority af women who do it will screen out negative, so they don't need to worry about it ( low false negative). But those who test positive are a much smaller group, and they are offered further testing to make sure it's ok.