The Catholic Church has always taught that abortion is a sin. The only way philosophical inquiries about embryology would make any difference, would be if there were a scientific dispute about whether they were dealing with a living human embryo, or not.
In terms of historic Christianity, the resolution of the embryological question did not make a moral difference, inasmuch as even if it were "just" contraception, it would still be a sin, intrinsically wrong, and forbidden.
Many (but not all) Protestants will still dispute about this, since, for instance, some think that the hormonal Pill is OK because it "only" blocks ovulation or it "only" blocks fertilization; whereas the Catholic (historic Christian) understanding is that direct sabotage of the transmission of life is morally objectionable, whether it occurs before, during, or after fertilization.
With the following qualifier....this was not opposing abortion from the moment of conception as Rome currently defines it.
Further, Rome only dogmatically defined this at V2....so there were no dogmatic proclamations against abortion prior to this thus calling into question the statement the "Catholic Church" has always taught abortion is a sin.
Many (but not all) Protestants will still dispute about this, since, for instance, some think that the hormonal Pill is OK because it "only" blocks ovulation or it "only" blocks fertilization; whereas the Catholic (historic Christian) understanding is that direct sabotage of the transmission of life is morally objectionable, whether it occurs before, during, or after fertilization.
And again Rome is in contradiction of itself on this as they sanction contraception through NFP.