The prophets of old gave stern warning against those who robbed from the needy and oppressed the poor. God, who lifts up the lowly, expects His people to do the same, and to ensure that they have enough.
That is why it is so easy to understand why we defend the unborn. If God wants us to make sure our brothers and sisters have enough of this world’s goods, then He certainly wants us to make sure they have this world’s most basic good, life itself.
The whole Biblical teaching about care for the poor would make no sense if we did not have an obligation to preserve the lives of those in danger. And we do this for the very same reason: God has entrusted us to the care of one another.