It is a distinction without a difference when applied to abortion. It becomes important in genetic research. The moral issue is convoluted with this fact.
“It is a distinction without a difference”
Wrong. Newt just became a Catholic a few years ago and is already a CINO.
It’s excommunication time!
Ectoptic pregnancy is not a uterine implant but fallopian or elsewhere.
It depends on how you look at the matter, as historical or prospective.
If you are asking when did I begin, obviously when you were conceived. It is certain that you exist, not at all certain that a fertilized human egg will get to live long enough to reach maturity. Let me put the matter this way: every human being who has ever existed assumed his separate identity when he/she was conceived.
But the question was not when pregnancy begins. It was when human life begins.
I suppose it is arguable that pregancy begins only at implantation. Yet I believe the evidence is that even before implantation, the fertilized egg is already secreting "pregnancy" hormones.
However this latter argument is a useless abstraction, akin to the argument over how many angels can dance on the head of a pin.
What matters is the human life that is extinguished, either by abortion, or by destruction of embryos in vitro.