I think thats fine, if you can schedule your appointments for as soon as you get back. Also, if you did have any emergency problems, god forbid, they'd treat you free here anyway.
A NT scan is used to calculate your risk of Downs. It involves taking several measurements of the collection of fluid at the back of your babies neck between 11 and 14 weeks. If you miss the dates for that you can always have a blood test instead looking at various blood markers known to be elevated in Downs such as alphafetoprotein.
Hope that helps, and CONGRATUALATIONS
