Can someone advise on what happens at the genetic counselor meeting?

UPDATE: We had our NT scan today and met with the genetic counselor. Our baby girl's heart rate is right on schedule, she measured perfectly and the NT was 2.3mm. They said everything looked "perfect" but they did not lower their PPV for us. They assured us that Natera is very accurate and they left the assessment at about 85% - 95% PPV for us. We were very surprised because we have been told separately that the NT scan catches 80% - 85% of Trisomy 18 cases. For ours to be perfect, and not move the needle at all, we were surprised. Anyone else have any similar stories?

My wife (27) and I (29) received a 91/100 chance of Trisomy 18 with our baby girl. We have a meeting with a genetic counselor in 2 days and would love some help with questions to ask or an idea of what to expect. This is our first pregnancy, and we really feel in the dark on this stuff. Our midwife has not been very helpful or responsive. Is the genetic counselor a prerequisite to the MFM? Does an NT scan happen with the genetic counselor?

Any experiences or advice is very much so appreciated.