last year, i was 7 months prego with my baby... and i was in line at Sears, some lady was smoking blowing it in my face... I snapped and said, I don't smoke and neither does my unborn child, she looked down, seen that I was prego and said *im sorry, i didn't realize you were prego* (i was wearing a thick poncho and had my purse in front of me) and she immediately put it out turned around and blew the smoke out of her mouth. i was shocked but appreciative.
as for other people, they dont care, all they care about is those items. i think people look at it as the one day a year they can push and complain and act like a child and they take advantage of it. I never realized it could be so fun.
I do suggest you pad your belly, wear a thick shirt or something. And push your way through, make it apparent your prego, some people still have kindness... i think.
depending on the store though, if you dont need a cart, dont take one. Last year, I had someone tag team... they stood in line and I went and collected the items I wanted, boy did that piss people off... but hey they were doing it.
Good luck!