The Didache is one of the earliest Christian works, contemporary with some of the New Testament writings; it was probably composed around the year 100 A.D. It condemns what it also calls
pharmakeia and goes on to say, "You shall not slay the child by abortion. You shall not kill what is generated."
The Epistle of Barnabas contains similar language, and Clement of Alexandria associates the destruction of the fetus with the destruction of love for humanity. Tertullian condemned abortion, and in the second century, a Christian answered anti-Christian allegations that Christians engaged in human sacrifice: "How can we kill a man when we are those who say that all who use abortifacients are homicides, and will account to God for their abortions as for the killing of men? For the fetus in the womb is not an animal."
Some modern defenders of abortion argue, wrongly, that Christian opposition to abortion is relatively new. They point out that ancient and medieval Christian writers made distinctions between the "formed" and "unformed" fetus, the time before and after "quickening" when some believed the soul entered the unborn child. Their assumption is that this distinction made early abortion--before "quickening"--acceptable.
Although these distinctions can be found in the writings of Sts. Jerome and Augustine, and in the writings of such later Roman Catholic theologians as Thomas Aquinas, they were never understood as offering permission for early abortions. St. Basil explicitly rejected the distinction between the formed and unformed fetus as beside the essential point. St. John Chrysostom attacked married men who encouraged prostitutes and mistresses to abort. "You do not let a harlot remain only a harlot, but make her a murderess as well."
Finally, it is important to realize the profound significance of the fact that we celebrate the feasts of the conception of the Theotokos and the conception of John the Forerunner--in addition to the Annunciation, which is the feast of Jesus' conception.