Listeriosis is an uncommon disease in humans. In Australia in 2003 the rate was three infections per million population for non-pregnancy Listeriosis cases and 4.6 infections per 100 000 births per year for maternal-foetal infections.
So if Australia has a population of 20 million, that gives approx 60 cases of listerosis per year in Australia.

There are approx 250,000 births per year in Australia. Therefore, 4.6 x 2.5 = 11.5 maternal-foetal listerosis infections/year

There are approx 1500 fatalities from road accidents each year in Australia.

So, statistically you are 100 times more likely to die in a car accident than by infected by listeria during pregnancy.

* i admit that the calculations are crude