Some things have changed. We now have DNA testing which, if used, would absolutely, positively prove that a mother and her fetus are in fact TWO separate human beings.
Another difference is viability. Though mostly ignored these days, the Roe decision was supposed to allow regulation of a viable fetus, and viability is moving steadily towards fertilization. At some point in the not too distant future, fertilization and viability will be the same event. At that point it'll be awfully hard for liberals keep abortion legal.
The real irony is that the majority of abortions are performed on poor black girls. The Democrats abortion agenda is a genocidal attack on their own constituency yet the race hustlers like Jackson, Sharpton, Hillary, Boxer, et. al. continue to cheerlead the whole program.
I don't get why this is a big deal. Of course we know that the baby is genetically distinct and unique. There's no need to do tests. But what follows from this? The woman's eggs and the man's sperm, because of "crossing over" between homologous chromosomes during their creation, are also genetically unique and distinct from the parent (even overlooking the haploid/diploid distinction), and even from one gamete to the next. So the gametes are living, human and genetically unique. Does this mean they can't be destroyed either?
I'm not necessarily arguing the pro-choice side of the debate here, but only suggesting that there is no purely factual or scientific "slam-dunk" argument that wraps up the pro-life position. There is no scientific answer, for instance, to the question, "when does life begin?" because life doesn't "begin" in any biological sense. Human life is always present and in process (allbeit with alternating haploid and diploid generations) at each and every stage in the reproductive process.
Reproduction is ultimately cyclical. In fact the cycles are even "nested," if I am corrected in recalling that a woman begins producing eggs while she is still in the womb. At best one can say that fertilization is the point were the creation of a genetically unique diploid individual (again the gametes are also genetic individuals) culminates. Now, that might be the proper point to extend the full legal protection of personhood to the developing life, but that case can only be made with arguments that go beyond the mere biological facts of the matter.
Another difference is viability. Though mostly ignored these days, the Roe decision was supposed to allow regulation of a viable fetus, and viability is moving steadily towards fertilization. At some point in the not too distant future, fertilization and viability will be the same event.
Viability of younger fetuses has been improved, but my understanding is that it's done so by approaching more closely and consistently a limit which is NOT apt to be surpassed in the "not too distant future".
It is at some point around the beginning of the third trimester (I don't remember exactly what week) that capillaries grow close enough to the terminal air sacs in the lungs for the blood to take up oxygen from the lungs. Before this the baby simply cannot get oxygen into its blood by breathing, even in an oxygen tent. It's blood must be run through a heart/lung machine of some sort. But even the most perfectly made machine will cause the blood to clot unless anticlotting factors are added. The problem with this is that, due to the development of the baby's circulatory system at this same stage, the thinned blood will cause internal bleeding, particularly in the brain, and this will kill the baby.
It's a catch-22 that may be surpassed at some point in the future, but not at present forseeably, and only with revolutionary advancement in techonology as opposed to the simple evolution of current techniques.
Besides, I don't think it's a good strategy for pro-lifers to even tacitly endorse the viability standard unless that's what they think the standard really should be (in which case they could probably be said to be adopting an intermediate position rather a distinctively pro-life one).