New job while pregnant?

Ca
Opinions please! I have an interview tomorrow for a great job opportunity. I need to know what I should do as far as letting them know about my pregnancy. I am 19 weeks, but this is my first baby so I'm barely showing. I know legally I don't have to tell them but I'm afraid they will hire me & then be upset. I'm trying to decide what is morally right. This job would be a great opportunity for me and I really want it! Please opinions!