I don't agree with Roe v. Wade overall, but I do think Justice Blackmun was right that we cannot know the instant at which life begins. In fact, I'd go a step further and say that there is no magic instant at which a cell or clump of cells goes from "not life" to "life". Even before the point of conception, a sperm and an egg have some life-like characteristics. Conception creates more such characteristics, and is the first moment at which a full blueprint for a life-to-be exists in one place. As the egg grows into a zygote then an embryo then a fetus, the extent to which a "life" exists grows steadily. At some debatable point, the life-to-be becomes a full-fledged life.
Unfortunately, I don't think there is any defensible way to discern the exact point when a life comes to be. Thus, I can't get around the fact that abortion law is inherently arbitrary to some extent, necessitating a balance between competing rights and policy goals. I know many of you find this untenable, but I'm okay with it.
Two big problems with Roe. First, even if it doesn't presume to decide when life begins, it does presume to decide when it doesn't begin. That wasn't their decision to make. It had nothing to do with the law they were supposed to be applying.
Second, if they're going to sit as drag state legislators (and if we're ok with unelected elites making the rules instead of democratically elected officials), they should have erred on the side of people living rather dying. But again, it wasn't their job to get into that issue. In terms of procedure, they're poorly equipped.