I just had the NT scan and bloods too babypink. We call it "combined screening" in NZ. With the scan they measure the amount of fluid behind the neck. This is often enlarged if baby has a chromosomal abnormality. With the bloods they check for a protein in the blood which can also be elevated with abnormalities. They put all your details (age, babies measurements etc) into a computer program and they just give you a degree of risk. Like 1 in 5000 I think I had with DS1.
It doesn't tell you gender or anything specific really. If you come out high risk then they offer you an amino here.