Sure, most educated middle-class white women will figure, "oh, those laws don't apply to *me*," and they'll go on to get good prenatal care, and their pregnancies will turn out fine (not least because, contrary to popular scare tactics, drinking or smoking or even drug use during pregnancy does not actually guarantee problems--the placenta is a marvelously protective organ, and most pregnancies where women drink or smoke or use drugs turn out fine). But also because we tend to assume--rightly--that we aren't the target of this kind of shit, and that if we accidentally get caught up in it, well, we can hire lawyers and explain ourselves and judges and juries will listen to us.
But educated middle-class white women aren't the only ones who have babies. Even though, if the statistics for pregnant women reflect those of other populations (and why wouldn't they?), whites are *more* likely to use illegal drugs than any other group except Native Americans. And, of course, the presumption that this kind of prosecution won't affect us is a direct rebuttal of the idea that we are all equal under the law--and sooner or later, some average white middle-class college graduate good mom is going to find herself in jail, like poor women before her, because she was unlucky enough to have a problem with her pregnancy.
And in the meantime, women who don't assume that discriminatory laws don't apply to them--mostly poor women of all races--will be faced with that choice: could I be fucking pregnant? And if I am, do I dare go see a doctor or am I going to get my ass arrested by doing that? And if you're poor and marginalized already, and you have a drug problem, and you lack health care, and god knows what other already-existing barriers to finding a doctor you're dealing with, that threat is probably enough to keep you putting off making that appointment. I know it would me. And then, if problems develop, you're fucked.
Go read the whole thing.