Career advice please - PromotIonal interview while pregnant


I applied for a promotion at my current job before I knew I was pregnant. They just informed me today that I've been selected for an interview. The promotion would be more money and a better title, but essentially the same work that I'm already doing and with the same people and boss. I just had an excellent annual review, so I think my chances are very good. My question is, do I tell them I'm pregnant?

I was planning to wait until 12 weeks (next week is 8), but now I'm not sure.

Legally, in this state they can't discriminate against me based on the pregnancy (and this is a legal office so they know that) but I would never be able to prove they did. Also if I am passed over, I don't want to have any reason to believe my pregnancy had anything to do with it. But I'm going to have to tell them eventually, and I don't want them to think I don't trust then to follow the law. Also telling them after this is going to be awkward whether I get the promotion or not.

So, what should I do? Thank you!