If she literally had her stomach exposed then yes, that's a bit much. However I find nothing wrong at all with a pregnant woman wearing a tight fitting shirt that's tight around the stomach. I mean, unless they wear some shirt out of a rap video, it's bound to be sort of tight.
I find some pregnant women to look sexy as hell. If they were fat before the pregnancy then chances are I don't think that. I personally find my wife, who's 8 months pregnant, very attractive. Of course I always do, but this is our second baby, and sometimes I think she looks even better with that huge stomach poking out...
It's weird. Someday you may understand, or you might have some fat preggo wife and think to yourself, "that Josh was a dumbass."