Before Christianity, abortion was also commonplace, and the only know method of birth control, other than, of course, killing the baby. Afterwards, it was obviously still practiced, but less openly.
If one thinks childishly in terms of theory of karma and abortion ignoring the near accurate scientific theory of Malthus ,he/she who forced abortion too should die in the same manner perhaps in his next birth.And suppose a person of authority advocated abortion for the general population,then that sin must be distributed amongst all those that go for abortion just like a modern day judge distributes the punishment for a crime that involves many criminals amongst all the criminals.Both the abettor and the participants in the crime get punished.
Now once upon a time in my life,I wanted to commit suicide due to loss of honor by slitting my wrist,but could not muster enough guts even for that.However I am not personally averse even today to die without much pain through euthanasia.
So while thinking childishly, I would definately not advocate killing a baby by boring its head skull with a vaccum machine and sucking off the brain matter etc,I would not be averse to family plainning by painlessly killing off the foetus or the baby,though I prefer condoms etc even more.Afterall more than 25,000 infants die every day in this world in a far more painful way of starvation as the omnipotent God does not choose to feed them all.