Pardon my ethnocentrism, but this is *bullshit*.
The Talmud worked through these issues nearly two millennia ago. One who pursues the life of another must be stopped, by death if necessary. A fetus endangering the life of the mother has no independent existence except as a pursuer — it will die regardless. Hence, it must be killed. A moral framework for determining what should be intuitively obvious.

Here is a lovely analysis of a recent, genuinely difficult case done by the late Rav Moshe Feinstein, on conjoined twins. Why the Catholic establishment is still contorting itself over cases as simple as the one here is beyond me.