I think you could go with either, but I would go with my obgyn.
You go to your baby doc for baby stuff. Obviously your throat has nothing to do with a baby doc so go to a regular doc. Just be sure to tell them your pregnant
When I was sick with an ear infection and the start of strep I called my normal doctor and they said since I'm pregnant and sick I need to go to my ob doctor because then if I need any medication the doctor can prescribe it without having to check with another doctor.