Do you know what triggered the position?
Well, it's complicated. And mainly down to the foibles of various popes.
In Ye Olden Days the generally accepted belief was that a fetus/embryo acquired a soul at "quickening". This happened at (based on Aristotle who appears to have just Made It Up) 40 days (male) or 90 days (female). This, BTW, is pretty much still the
general belief within Islam, at 120 days.
Other, pre-xian, cultures and religions tended towards ensoulment at birth (the 'first breath' standard) or occasionally at conception.
Aristotelianism was incorporated into xianity by the Church Fathers (e.g. Aquinas, Augustine, Jerome and Tertullian) and if you look at the history of the discussion on quickening and ensoulment it's a mess of arguments between these believers and those to wanted to incorporate the rival Pythagorian doctrine of ensoulment at conception.
About a thousand years now passes and we reach Aquinas who reignited the debate, paralleling the reintegration of Aristotelian learning into Europe, by being pretty definitive that ensoulment was well after birth. Hence abortion was, as in he Hebrew tradition, a misdemeanor.
Matters continued along these lines for a couple more centuries until Sixtus V who, in 1588, issued the Bull Effraenatam, which subjected those that carried out abortions at
any stage of gestation with automatic excommunication and the punishment by civil authorities applied to murderers.
This lasted three years until his successor Gregory XIV limited that mandatory excommunication to abortion of a "formed" fetus. This
may demonstrate Jesuit influence as the doctrine of ensoulment after birth was pretty common among them.
Another century passes and Innocent XI condemns the Jesuit teachings but doesn't actually promulgate the doctrine of ensoulment at conception.
Finally we reach the nineteenth century and the medical organisations (such as the nascent AMA) who engaged in a power-grab over midwives, whom they really didn't like and blamed for carrying out terminations. Suddenly civil society started getting in on the act and the first severe restrictions on abortions started being enacted. That's when (in 1869) Pius IX staged an abrupt about-turn in four centuries of church doctrine, and Canon Law, with Apostolicae Sedis, and re-enacted the penalty of excommunication for abortions at
any stage of pregnancy,
This was very much down to the man himself, who'd undergone an equally abrupt change in views following certain matters in 1848, like being chased out of Rome by the republican revolutionaries and only returning with the French Army.
He spent the rest of his life descending into knee-jerk conservatism, condemning liberalism, modernism, moral relativism, secularisation, separation of church and state and other such dangerous ideas.
Abortion was really only a tiny part of this process.
Hope this helps.
It doesn't change the fact THEY LIED.
