What happens at your first high risk appointment? Possible mo/mo twins.

Next week I have my first high risk appointment with a different ob and I'll be 14 weeks and 6 days. I've already had 4 ultrasounds done and they haven't been able to confirm if my twins have one or two sacs. The receptionist said it'll be a 3-4 hour long appintment. I know they're doing an ultrasound with a better machine but what else should I expect? Thank you in advance.