Food restrictions in our days

Kar
I wonder why the "dont's" in pregnancy have become so strict in our times. My mother tells me that back in her time the only restrictions in diet were alcohol, cigarettes and coffee. Nowadays it is also fish (even cooked) and seafood, pastrami, fresh mushrooms, unpasteurized cheese etc. I'm sure there were viruses and bacteria 30 years ago as well. But there weren't so many restrictions for pregnant women!