Going into OB/GYN is a huge plus when you're pregnant during interviews. I was 7-9 months pregnant during interview season and aside from having to limit where I applied so I could drive to all my interviews I thought it went well. It made me stand out, that's for sure. People always remembered the pregnant girl. All of the programs I applied to were very accomodating when I was there, letting me take bathroom breaks or skip the tour for example. I did not tell them I was pregnant in my application or when scheduling interviews though. I turned down a few interviews because they were just after my baby was born and I didn't want to travel with a newborn.
To me, if the program would have made me feel uncomfortable because I was pregnant then I didn't want to go to that program anyway...but I didn't experience anything negative.
Be prepared for lots of questions, mainly how far along are you, how has it been, do you think this is helping you to connect better with your patients, etc. Not one question about other baby plans, which was nice. PM me if you have any more specific questions.