Didache 2:1–2; "The second commandment of the teaching: You shall not murder. You shall not commit adultery. You shall not seduce boys. You shall not commit fornication. You shall not steal. You shall not practice magic. You shall not use potions. You shall not procure [an] abortion, nor destroy a newborn child"
Many protestant groups do not accept the Didache since it is not apostolic in origin, but it does demonstrate that the Catholic Church has been against abortion from the beginning.
First communications from God to Man is in Genesis 1:28 is to go forth and multiply. This the first order of business. The first issued order that has no caveats or attached stipulations. How would God want Man to behave in any way that would not move that forward?