One example - true story. A devoted couple had six children. They practiced 'Catholic birth control' but she became pregnant again. Her health was precarious and her doctors warned her that bearing another child could easily mean her death and that of the new baby. As a good Catholic, on the advice of her priest but against the wishes of her husband, also Catholic, she went forward. She and the baby died. The husband and the six children quickly left the Church to attend elsewhere (Episcopal). They blame the Church and even the priest. A grieving and bitter husband and six young motherless children, none over ten.
In such an instance, many Christians of all persuasions would follow their consciences and go along with an abortion - the lesser evil. To begin with, the position of the Church hasn't been constant. As I recall, Augustine and some other Church fathers believed that an embryo was not an actual baby until after the first two months following conception. Then, too, many believe the baby's soul, if one is already present, would spend eternity in. heaven.
One friend added to this all the God-approved murders in the Old Testament. God drowned all humanity, including children and babies yet in the womb, in the story of Noah. He commanded Joshua to slaughter all the inhabitants of Jericho, order Saul to go and murder every living Amalekite, etc. There are verses in Exodus that call for the execution of witches and all who don't worship the Lord (see Ex. 22:18, 20), etc. As I recall, that great Doctor of the Church, Aquinas, proposed the execution of heretics.
A very complex issue. One might consider the 'judge not' words of Christ, who never addressed many such issues forthrightly.
I am generally against abortion except in a few rare cases. But I also have some sympathy for those women who are faced with heart-wrenching decisions. May God bless them and the rest of us treat them with compassion, even when we take issue with their decisions. Let those without sin cast the first stones.