S.C.
With my first child, 7 years ago, I found out I had a final interview scheduled while I was in the hospital. I went in one day to get my blood pressure checked, and it was so elevated that they kept me in the hospital for a couple of weeks before they induced me. My family was bringing my mail to me. I was going to call to decline the interview and a lot of people in my life suggested that I should go. So, I spoke to the doctors, and they agreed to let me out of the hospital for a couple of hours as long as someone drove me there and I came straight back. My mom and dad brought my interview clothes to the hospital, and drove me there. They were so impressed with my interview and my writing skills (pre-work) that it did not make a difference. I was given the offer shortly after I had my son, and they asked me how long I would need for maternity leave. I had my son in December 2001, and started work there in March 2002. I worked there for 5 years.
It seems once I get pregnant, I leave a job (as if the event is not stressful enought). With my second son, 18 months old, I was going through the interview process while pregnant with him. This was a little different because I was not showing yet. I got advice from various HR people and friends, to just go through the interview process without telling them, and if I get an offer, then to let them know. I followed that advice, got the offer letter, then at my pre-employment physical I told the doctor that I was pregnant and to feel free to let the employer know. I then called them and said I wanted to work out a plan so that my maternity leave would affect them as little as possible. I worked for 3 months, and then went off on maternity leave for 4 months. My boss suggested that I take all the time I needed, because once I was back to work, I was back to work. It worked out great. I kept in touch with him during my leave, just to keep the ties going.
I say all of this because each circumstance is different, and we should act depending on the circumstances. If you go into that interview pregnant, but show confidence and ability, you will make them forget all about you being pregnant, if it crosses their mind at all. With the bad economy, just think about getting the job and the fact that you have this opportunity. If the job is for you, you will get it. On the other hand, if they are going to hold pregnancy against you, that is a company you don't want to work for because they will end up giving you grief when the baby is sick, or you have to go to an event with your child.
Good luck and I hope all works out. I think it will. It did for me twice.