Hi bubbles, when you go to see your ob, he or she will probably do a scan on your first appointment. They then give you a referral for the Nuchal Translucency Scan for between 11 and 13 weeks (if you choose to have one).
If you are going to book into an Ob, it's best to do it right away, as they can fill up pretty fast!
By the way, congratulations on your pregnancy!