sandy: best is ask ur gynae.. what s/he thinks. If s/he recommends you go, then go for it.
But for my gynae.. somehow he only does the NT scan. From NT scan, then you can decide if you want to do more scans like OSCAR or Triple Screen etc.His explanation to me is that.. even oscar test is not 100% accurate. NT scan at the right timing (between 11 to 14 weeks) can give you a pretty good gauge if your baby has down. And most importantly, he said it's non invasive so he does it.. cus it's just scanning and checking baby's neck fluid. (below 2mm = normal) Above 2mm = higher chance of down.. then he will recommend u to do more scans that are more invasive such as drawing blood, amniotic fluid all these which have a slight risk in miscarriage or infection.
I am happy with my gynae's explanation on all these tests and since i trust him as my gynae, i listen to his recommendation. Although he told me if people still wanna do the oscar etc, he won't stop us cus it's up to us.
If you really really wanna go for the test, just book it to have a peace of mind.