I agree that you should avoid the salad stuff, or the "hot" food that has been sitting there for a long time (this includes food at other takeaway places that sits under hot lights for hours). But, if you grab those potato skins as soon as they are brought out, I'm sure you'll be fine.

The other thing you can try (which I have done successfully at a hotel breakfast buffet) is to explain that you are pregnant & can only eat food made fresh. They cooked me my own bacon & eggs - rather than serving me from the buffet.