What's going on at this doctors visit?

Breezy❤️
So at my prenatal appointments, the nurses always book my next couple appointments in advance. 
So I went to the bathroom and my mom got the paper from the nurse and when I came out she told me that she picked a certain doctor for the 36 week visit, because I had to see a doctor that week. 
What's going on at the 36 week prenatal check up that requires you to see a doctor?