S.C.
I have had this situation with both of my children. I tend to do things the hard way and have changed jobs both times that I was pregnant. With my first son, who is now 7, I was going to decline the interview because I figured they would not hire me but that is why you never say never. I was picked out of six other candidates and they waited for me to return from maternity leave to start.
With my two year old, by the time I got called for the interview, I was not showing yet. I was conflicted and got opinions from a lot of people who most of said to not let them know until I received an offer letter. At that point, they said I would still be able to give them enough time to prepare for my absence because I would not actually have the baby for another six months. That is what I decided to do and I felt good about my decision. Once I received the offer letter, I informed the staff in my pre-employment medical exam that I was pregnant and that they were free to tell the employer.
I called my future immediate supervisor after they received the medical report and said that I wanted to start planning for my absence. I think you should do what you feel is right. Some employers will not discriminate, as you can see from my first experience, but there are those that will and you never know which one that will be. Go with you gut and what you feel is right. I felt very good about my decision once I got other opinions. Most of the opinions you may get may say to let them know. You will have to make the call. I don't think that not be forthright about this makes you a liar unless they specifically ask you on the interview if you are pregnant, which they would not do. Your pregnancy actually has nothing to do with the interview process and your ability to do the job, unless it is something stenuous.
I love the job that I have now and would have been crushed if the only reason I would not have gotten it was because I was pregnant but I will never know if that would have been the case or not. The HR Director told me when I was hired that she probably would have done the same thing.
My two cents.