Why "Save the zygotes" is a Strawman Argument

(No, I'm not really here, I just didn't want this post going up on Pentecost Sunday. If I'm distracted, it's with other things!)

I don't know if you have heard or read this argument (in favour of all means of sterilizing the marital embrace) — I ran across it via a fellow tmblor, on a patheos site (both of which mean I won't be linking to it, here...); but, anyways, the argument runs "The human fertilized egg [miscarries before] implantation 18% of the time. But fewer conceptions means fewer dead zygotes. Therefore the [Catholic|Humanae Vitae] position is {wrong/hypocritical/safe to ignore}."

I'm not making up that "18%" statistic either. Of course, you will find here other samples of my epistemic scepticism; so there is an interesting question: "How do you know that 18% of human pregnancies miscarry in the zygote phase?" It breaks down into: how do you reliably count conceptions before implantation? I'm glad (for myself) that I shan't ever be on a medical science ethics review committee, but one wonders about who is, sometimes... I can believe, for instance, that 18% of IVF-attempted embryos might miscarry. You can count those, even if the first number is immoral. I can believe that 18% of amenorhea might be isolated events...

I don't know either of those statistics correctly, but it isn't really pertinent. Because: I'm pretty sure the statistcal premise of the argument is actually a distraction. A worm on a hook, as it were. The premise that contraception is a successful preventive of miscarriage, on the other hand... Never mind that it might be a lie: it doesn't even make sense! Contraception "prevents" miscarriage about the same way that an empty field "prevents" potato blight in the field. If one wants to "save the zygotes", he should work on finding ways to improve the odds of implantation, and not on making sure there is nobody to implant. Again, how one works on improving those odds when it isn't clear how to legitimately measure those odds, I don't... but anyways.

But there is another perspective a Catholic can take: given that one can't have a child born without attempting to conceive, and given that some attempts to conceive succeed but nonetheless miscarry, the resulting change in Creation is another soul in Limbus infantum. For all that it is better for a given soul to be in Heaven rather than Limbo, it is still better for that soul to be in Limbo than in Hell; and I can't see that it is better that Limbo be smaller on account of there being fewer souls.