Well, you shut down people who are openly providing abortion services, and as far as prosecuting women go, you keep to the same standard that crime ought to be proved to - beyond reasonable doubt. If it's plausible that it was a miscarriage, then you can't, and should not, convict. Yes, that means that medicated abortions will still be relatively easily available, and probably impossible to convict, but being able to completely enforce a law does not mean that the law has no validity.