I would talk to HR about it - since it'll be obvious and it makes the potential transfer to the new position tricky.

The supervisor will want you to transfer to the other dept. Once the company knows, the hr knows, so it is the resposibility of the hr

If your co-workers can tell that you are pregnant -- as you noted your 6mo along -- then the hiring manager will also notice.

If you were offered it, would you take the job then take 3mo maternity leave? It seems like a bad situation all around...

I'm a little confused -- is your pregnancy physically obvious? If so, I just wouldn't worry about it at all as they'll know when they see you.

Regardless of whether it's obvious and regardless of what your current supervisor has to say about you, I personally would want to be the one to break the news to my current supervisor that I was considering or had been offered a transfer. (Ideally I would want the offer first, or a strong indication it was coming.) I would think the hiring manager would understand that, and would respond to some normal questions about next steps in the process. You can even say, "When you're ready to talk to my supervisor, please just let me know so I can break the news to him in person: we have a great working relationship and I think he'll be sorry to see me go." Or whatever phrasing sounds natural from you and not like you're trying to manage what your supervisor says.

I have no idea whether it's legal for your supervisor to share health news when contacted, but we all know it happens.

Good luck!

I work for a rather large company and an opportunity has opened up in a different department. I have recently disclosed to my supervisor that I am expecting and many of my coworkers also know (it's more than obvious, as I am 6 months along). I have an interview for this new job in another department, and am afraid that my current supervisor will disclose that I am pregnant if the hiring manager calls to ask about me. I had not planned on telling my supervisor about applying for the other department (figuring he'll find out if I get far enough along in the process), but should I re-think this and let him know that it would not be ok to disclose my pregnancy?