That's a good question and I'm not sure what the answer is. Something is telling me that on principle it should be illegal and that we should do what we can to prevent it from happening.
What, even though you regard abortion as the murder of a baby, and following your principle of making it illegal would lead to more abortions? Your principles are more important than stopping baby-murders?
If there were statistics that showed that countries without any legislation against rape had less instances of rape than in countries with legislation against rape, would you want to change the law so that it is no longer illegal to rape?
But there aren't, are there? Evidence that decriminalising rape would lead to less rape is non-existent, whereas evidence that liberalising abortion laws leads to a drop in abortion rates, and a particularly sharp drop in late abortions is already in front of us.
So what say you about that? Stick to your principles even though it leads to an increase in something you regard as evil?