To elaborate on what Nathan said, the early church was against abortion. The Didache is one of the oldest, if not the oldest non-Bible Christian document out there. Among other things it says:
The question then, was when does life begin? This developed as our knowledge of conception and pregnancy grew. St. Augustine I believe speculated that the soul entered the body at quickening. This should not be taken as endorsement of first trimester abortion, but rather a question of the science at the time.