It's funny as I was wondering the same thing. At my last u/s, I measured 2 1/2 weeks ahead of EDD but since I know for certain when I conceived, I'm sure we kept the original due date.
hehehe just finished reading your last post here...about both dates are accurate LOL
yeah you are supposed to go with the original date but of course you will go earlly :O) I'm so excited for you :O)
I think though that even my first U/S he put me a day ahead of my u/s....don't guess it matters anyways cause according to the last u/s both dates are right...Jacob measured according the the date on the u/s and Mekaila measured according to my EDD...
the u/s go up and down depending on growth spurts... you usually go by your first u/s and then stick with that date.. the earlier ones are more accurate at dating since all babys will grow at different rates and different times...
since you are having twins it probably doesn't make any difference in the world since you'll more than likely go earlier than your edd anyway!