I wouldn't tell them a thing.

Interview for the position. Show them why they should hire you and your qualifications.

I made that mistake years ago when I was upfront and honest that I was pregnant. I wasn't hired for positions that I was even over-qualified for. As soon as I didn't tell them I was pregnant - I was hired.

Being too honest gives them a reason to be discriminating. Even though it's illegal, it's hard to prove when you're interviewing.