First Specialist for pregnancy appointment tomorrow ! What to expect ?

I'm going in at 9am for my first appointment to see my specialist for an ultrasound ( I have to arrive 15 mins earlier ) since its my first to do paper work & need to bring my ID and Medicaid card . BUT I was wondering what really goes on ? Like your first visit , what happened or what ? I know its like seeing your OBGYN but Still I am wondering and so I know what to expect & at least have a clue on how long this visit will be .

Ill be startint my Pregestrone shots soon ( due to my 2nd pregnancy going into preterm at 29 weeks ) I guess thats why I am seeing the specialist but anything helps thanks ! I'm currently 18 weeks 6 days .