wlilian: Im doing my OSCAR on 21/1 too. 9am at TMC. Frankly speaking, I cannot really remember what they did exactly for my #1. Haha. All I know is that they would do a scan and a blood test. For my #1, my husband had to do a blood test too, but Im not too sure whats that for though. So, I did a search on the internet. This is what i got from BabyCenter.
Nuchal translucency is a collection of fluid under the skin at the back of a baby's neck. It can be measured using ultrasound when your baby is between 11 and 13 weeks and 6 days old. All babies have some fluid, but many babies with Down's syndrome have an increased amount.
The NT scan can't tell for certain whether your baby is affected. However, it can help you decide whether or not to have a diagnostic test.
The blood test measures:
•free beta- hCG (human chorionic gonadotrophin)
•PAPP-A (pregnancy associated plasma protein A)
A woman who is carrying a baby with Down's syndrome will have abnormal levels of these two substances in her blood.
I hope this helps!