It's actually less defined than that. It's about 150 cells arranged in a sphere. If you've ever raised frogs from eggs, you've seen cell division, and you can imagine what this looks like. As you've said, this isn't a question of abortion. These are embryos that will be discarded. The fundamentalist response seems like some half-baked attempt to modernize the Onan fable. Thanks to science we know the grim prospects of a single sperm, and what a mischaracterization, based on the understandable ignorance of the time, the idea of the precious “seed“ is. We know that even in the course of what Christians consider legitimate gestures of procreation millions of sperm (a “potential life”) will be “wasted” as a matter of course. Again, Christians can't look to the bible to find a description of the world that is: they can only try to reconcile their interpretations of primitive misapprehensions of the world with what the data actually tells us today. There are no sperm or eggs in the bible, not because god wanted to spare us the gory details, but because the men who wrote it, predictably, hadn't the slightest idea how anything worked. They simply insisted on dogmatic ideas that advances in standards of practice in science and logic have rendered laughable. I don't know why the soul at conception concept should be treated any differently.