here is a good statement from the Catholic Physician's Guild supporting the Bishop's decision and affirming that abortion is never justified by circumstances, or by intended end.
"An action which is in and of itself wrong ... is never justified by circumstances or intended end."
"A medical procedure, where the direct intention is the termination of pregnancy, is an abortion."
This second quote would be better phrased as: "an intentionally-chosen act that is inherently ordered toward the killing of a prenatal is a direct abortion" and is therefore always gravely immoral. Intrinsically evil acts are always intentionally chosen, but the intended end may differ from the moral object (the end toward which the act is inherently directed).