Sue, congratulations! That's wonderful news! And sounds like you've got nice strong betas there too! I can't remember at what point an embryo splits to make identical twins, but if it's after 5 days then there's still a chance that you could get them with a SET. How did you calculate your due date online? Did you use LMP or O date? If you did a medicated FET then for a 5 day transfer you just count back to 5 days before the transfer and use that as the O date. That should give you the most accurate due date. You should get a dating measurement at the first scan, so you could always just wait to see how that comes out.