So does abortion. Abortion says, "adult lives are more important than unborn children". Also, do you really think it's unreasonable to elevate the life of a human child above a single-cell infectious disease or a worm?
Yes I understand the concept. My point remains though that a foetus is a parasite which is intended to be there. The female body has evolved specifically to be able to contain it and allow it to grow, whereas it will attempt to destroy any other parasites or intruders into it.
I assume you're talking about rape. I realise it's a very sensitive subject but this is another example of valuing one life over another: "I didn't want the child, I was assaulted and now have to carry a child and birth it, and that is too traumatic. My need is paramount so I will kill the child to avoid further trauma." I'm not saying I know the answer to this situation, I'm just making the point that even in this situation abortion is saying that one person's life is more important than another.