quote: The event of fertilization itself means the deed is done!
No. The fertilized egg (a cluster of rapidly dividing cells) has to implant in the uterine lining, or in another healthy body tissue, and grow there, or no significant development can occur—no source of nourishment and waste removal for the growing embryo otherwise, and the fertilized egg will just run out of stored energy and start to disintegrate and pass out of the uterus and be discarded in the environment where other uterine fluids and shed cells go. That’s one reason some believe that IUD’s, which create an environment hostile to uterine implantation, are a form of abortion.
I think we're actually in agreement here. When I said "the deed is done!" I didn't mean that the continued career of the newly-started son or daughter is now a cinch. I just meant that human life has begun-- or, if you prefer, it has been "passed on" to a another generation.
Day One in the life of anyone, is the day that fertilization occurred.
After that, the new small being has to implant on some suitably flexible, vascular organ (usually the uterus) where it can nidate ("nestle in") and get busy developing its own next set of tissues, organs, and systems.
I am among the many who would argue that an IUD is an abortifacient, because it kills the new human at this stage by interfering with implantation. As well, hormonal contraceptives which can cause almost imperceptible embryonic loss by driving down the necessary level of progesterone --- it's actually more complicated than that --- are also on a moral level with abortion.