Yep, the entire usage of a word was altered from the common, aeon-long definition (even if not in current-day English) to account for a recent, comparatively rare, event - artificial insemination and all types of extracorporeal generation of life.
The natural should trump the artificial and manipulated for terminology. New phenomenon, new term.
Regardless of the definition of pregnancy - nothing is changed as to the nature of the embyro.
Actually, it is possibly an important question as to which was the change in an aeon-long definition.
During the patrisic era, the understanding of 'conception' was analogized to a seed being planted in the fertile soil of the womb. One speaks traditionally of a woman conceiving, and applies the usage from the moment of implantion--a sign of which is the cessation of menses. One does not speak of the woman conceiving if egg and sperm join, but the embryo fails to implant and leaves her body, because the (very common) event is unobserved.
While I think the Latin church's conclusions on the matter are generally sound, I think they have been arrived at in too facile a manner, by accepting a medical redefinition of conception as fertilization--either conception = fertilization, or conception = implantation, was really a redefinition, since no distinction between the two was known until the application of microsopy to reproduction--without fully considering the patristic and Scriptural testimonies as the Fathers, evangelists, apostles and prophets understood them.
Under the new circumstances, may it be that a distinction like the formed/unformed (rightly rejected by St. Basil the Great as applied to children gestating in the womb) might rightly be applied to pre-implantation/implanted? That abortion (meaning of an implanted embryo or fetus) is murder, but that the destruction of an un-implanted embryo is a lesser sin? (It is the case that most embryos don't implant (!), and while it may be God's will to create many, many human beings who never have the chance of finding grace in Christ because they died as little spheres of 8 or 16 genetically distinctive human cells, more of them indeed than human beings who have walked the earth, it seems odd indeed to my still-passionate sinful human mind. So odd, indeed--as the Psalmist tells us, He does not wish to destroy the works of His hand--that the fact may matter to our moral understanding of the matter.)