What to Expect when going to see specialist?

This will be my first appointment So Ill be going to the specialist next week Monday , they wanted me to go in for an ultrasound .

Anything else ill expect ?

Or is it like going to the OBGYN ?

I'm going due to going into preterm labor at 29 weeks with my daughter and this will be my 3rd pregnancy ( if that helps ) & I should be starting to get my shots as well , was it weekly ? Or Every 2 weeks ? And how many times would you see specialist ?

Thank you 😊

And btw I'm 18 weeks 1 day Today !