If the story is true, I agree it's inappropriate for Derick to visit her at the birth center. I used to work at a medical building and if Mr. BitterApple came by to take me to lunch or whatever, he would wait out front in the car or meet me in the lobby. Nobody's spouses came into the waiting room of the doctor we worked for.
I don't know much about birth centers vs. hospitals, but I'm assuming that sort of behavior would be frowned upon, particularly in a maternity ward.