Seems reasonable to me.
If I try to kill myself by poisoning Thanksgiving dinner, I'd certainly be charged with murder if I survived and my guests didn't. Don't see how this is any different.
English
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Poisoning food that you know other people will eat is illegal, though. Poisoning yourself isn't.
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A pregnant woman poisoning herself is knowingly poisoning another person--her baby.
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At this point the fetus is considered a human in the eyes of the law, and you could say she knows the fetus will have to "eat" the rat poison