HMOs and gynecologists?

I am switching to a new medical plan this next year. I had to pick a primary care physician when I signed up and I did. Well I know i have to go through her now for coverage, but what about my gyencologist? her office says they have my plan available but I dont know if I can still go since i am switching to an HMO. Can I still go to my old OBGYN with my new plan?