I would say YES, it is abusive. It infringes on the rights of the unborn child. FAS is absolutely terrible! After seeing kids with FAS, it's reason alone to abstain from drinking. It's such a tragic syndrome and you never really know what you're going to get. I have a friend who's mom smoked, drank heavily, did drugs, the works while she was pregnant (she was basically in denial of her pregnancy) but my friend turned out just fine and it inspired her mother to really turn her life around. But on the other hand, my mom has worked with numberous crack babies and FAS cases (my mom worked at an adoption agency and now an inner city daycare) and their mothers couldn't care less, obviously since they didn't even have enough sense to properly care for themselves.
There was actually a Law and Order episode on this very topic. The question raised was a good one: if it IS considered abusive, what do you do with the pregnant mother? Do you jail a pregnant woman? How can you possibly keep her from drinking/smoking? I'm not saying these difficulties mean that it shouldn't be law, but it does make it harder to address.
As for the argument that it's hard to know that you're pregnant right away, I say sorry, no excuse there. If you're responsible enough to have sex without sufficient protection, then you're responsible enough NOT to smoke or drink AT ALL b/c yes you might be pregnant.