Either that or the fact that we worry too much. What, exactly, is the risk of listeria when pregnant? And how different is that risk from the risk to people who aren't pregnant? If the risk is negligible in the first place (I'm not saying it is; the word 'if' is important there) and not much less negligible during pregnancy, it still isn't a big risk. I know this reasoning is not applied to other health risks we are told about (not by the media, anyhow), so I wonder if it has been applied here.
I agree that one's body does 'tell' you what is not right during pregnancy, to a large extent. It seems to be true that a lot of people are not body-aware though, and maybe that's the real problem.