The baby is innocent. The abortionist is not.
Now, why not hang the mother? Well, the answer is that it's demonstrable that the newborn thrive better with a good stiff shot of mother's milk for several months.
So she gets off the hook for a period of time ~ but I bet she doesn't go back to the abortionist if he's out there hanging from a lampost.
Remember, part of the practice of justice is to minimize the cost of maintaining a just system. If you hang everybody who violates the codes you run out of people. It only takes a few good examples to get the others to fall into line.
Signing off.
Carry on. :)