Both cited saints were firm opponents of abortion. St. Thomas Aquinas considered it to be a "sin against nature to reject God's gift of a new life." St. Alphonsus Liguori stated that "directly impeding the life of a human being is a grave sin, and a still graver one if the fetus is animate."
During the opening scene and the talk between pope Pius XIII and cardinal Spencer in the Sistine Chapel there are some lines spoken by Spencer (and not contradicted by Pius) that suggest that the Church allowed abortion in earlier centuries. While it is true that there have been vivid discussions among scholars and bishops about the nature of life and the moment of becoming an immortal soul in the mother's womb the teaching of the Church regarding the matter of abortion remains unchanged since the 1st century. Evidence of that can be found it the earliest Christian documents: the New Testament, the Didache and the Letter of Barnabas.