Maggie, thanks very much for an excellent article! I'd only quibble with one final bit towards the end of the article when you write:
If you go by the scientific definition, where pregnancy begins at implantation, then IUDs definitely don’t work by causing abortions. If your religious beliefs lead you to think pregnancy begins at fertilization, well, the data suggests that, sometimes, rarely, IUDs used as birth control might abort a fertilized egg
It sounds here like you're drawing a contrast between the "scientific" and "religious" definitions of when pregnancy begins. To say the obvious, while some persons believe that pregnancy begins at fertilization for purely religious reasons, there also exists a secular scientific (i.e., non-religious) argument that pregnancy begins at fertilization. If you'd like to read some literature on the topic (that is, for the non-religious argument that pregnancy begins at fertilization), I'd recommend Robert George (of Princeton) and Chris Tollefsen (of USC's) book "Embryo: A Defense of Human Life". (The book's main topic concerns the morality of embryonic stem cell research, but chapters 2 and 8 [if memory serves correct!] present the scientific argument for the claim that pregnancy begins at fertilization).
I don't know how strongly you intended to draw the contrast, but if George and Tollefsen are right then it's not the "religious" definition of pregnancy vs. the "scientific" definition of pregnancy - there are scientific arguments both for the belief that pregnancy begins at implantation and for the belief that pregnancy begins at fertilization. But since you were discussing the Hobby Lobby case (and its litigious context), religious beliefs certainly did come into play in this instance, although they need not have.
That quibble aside, though, I really appreciated your article - there's a lot more heat than light on this topic and I think your efforts will help rebalance that ratio in the direction it needs to go. So thanks for your hard work and I hope you have a good day!