Applying for jobs while pregnant.

Samantha
I quit my full time job about 2 months ago, at about 15 weeks. I was having problems with the heat and the physical labor, it was a factory job and I was working 12 hour shifts. I started looking for a part time job a few weeks ago, and had a interview at Kroger last week. I didnt tell them I was pregnant because I didn't want that to affect their decision that early on in the interview process. I know legally I don't have to tell them, but I wanted some options on when everyone thought I should tell them. I'm now 23 weeks and the job I'm applying for is in no way physical demanding in a way that could affect the pregnancy. Anyway I go in tomorrow for a second interview with the head over the area I'd be working in if I get the job. When and how do you think I should approach telling them?