Why is it seen as a criminal offense to have a very occasional glass of wine if you're pregnant?

Women have been drinking very lightly (and I mean not more than one drink) and very infrequently (I mean not more than once every few weeks) for hundreds of years during pregnancy with no known harm or consequence. Many European countries advise pregnant women not to exceed one drink a day. Many American doctors say it’s ok to have an occasional glass of wine after the first trimester of pregnancy. I don’t understand why people are SO judgmental and panicked about this these days. Why the stigma? Again, I’m not talking about drinking daily (or even weekly) or drinking several drinks at any one time.