This could be a push button topic due to beliefs on when is a baby considered a baby. If that makes any sense. It actually doesn't to me.
I don't think that matters in this case, because it has consequences if the baby is actually born. I think there should be restrictions placed most definitely for the sake of a future child, which does not matter whether or not it is defined as "alive" at the present.
But if they wanted to make this law for alcohol, they'd have to do it for everything else, like smoking. Smoking may be harder, because that essentially requires you to cut it cold turkey if you find out that you're pregnant. My mother managed to at least, so I'm glad for that...
A different solution would just be to rally the industry together and create a "We don't serve pregnant women" rule at bars, but I highly doubt that would work out as easily as the video game industry making it a policy to not sell M-rated games to minors.