I agree Cod the worlds gone mad, maybe all pregnant women should be allowed to eat are those sterile meal things astronauts have, mmm tasty.
Listeria is very rare nowadays, you would have to be unlucky enough to eat food containing it, then it's got to contain enough to make you ill (very rare IME), then it's got to survive your stomach, grow in your gut, cross the placenta and damage the baby, very rare I would say.
I don't avoid anything when pregnant (well apart from alcohol which is very safe, oh the irony) pity we couldn't douse all food in alcohol that would solve the problem