In reading the title of Foot's article and admittedly not having much familiarity with the doctrine it refers to, I was disappointed to find how little this article actually pertains to abortion specifically. Instead, Foot uses abortion as a springboard into a discussion of killing versus letting die and how the doctrine of the double effect often conflicts with our intuitions regarding what actions are right and wrong when two agents (a mother and her unborn child) have tethered fates. While the conclusions she ultimately draws are ones I would likely make myself if I had the mental fortitude to devise the arguments which beget them, I think her work here would benefit greatly from some manner of argument which didn't rely as heavily on her readers' intuitions as it does in its current state.
Many of the intuitions Foot appeals to are those I personally hold, such as the morality in killing a fetus to save its mother's life should not abstaining from action entail the death of both, despite their contradicting the doctrine of the double effect (which is to be expected as I share Foot's reservations about the doctrine itself). The problem, however, is that I'm not sure the examples she provides are quite as persuasive to those who don't hold those intuitions as she may hope. What seems absurd to those of mine and Foot's camp may not to those who hold that the ending of one's life being a primary intent fueling another agent's ending of that life is never permissible. This is particularly true in the third example Foot brings up in which refraining from intervening during a birth will result in the death of the mother but the survival of the child (whereas before, abstention resulted in the death of both parties) while intentionally killing the child will leave the mother alive. Foot remains ambiguous as to what intuitions she holds on this case, and instead uses it to show that while advocates for the doctrine often will invoke it here to defend letting the mother die, she feels their justification is actually misguided, that they should be appealing to a distinction between “avoiding injury and bringing aid” rather than “direct and oblique intention” as the doctrine originally states. This is the main conclusion she reaches with her paper, though it as well relies on a possibly contestable intuition: a distinction between avoiding injury and bringing aid.
While again, my intuitions are actually in-line with Foot's on this point, it should be noted that there are those who don't acknowledge a distinction. For a very Philosophy 101 example, there's Peter Singer's work on the immorality of miserliness in the face of suffering, in which a strong variant of his argument could state that not supplying whatever aid one can muster to those in need is indeed immoral. Though I don't think Singer himself posited this view, it seems possible to me that one may hold that such miserliness is of a similar caliber of heinousness as directly ensuring the wantonness of the needy. Such an intuition doesn't seem to bear much weight on Foot's first two examples, but it would seem to nullify the dilemma present in the third. Furthermore, if this irregular intuition was something that one held, Foot's distinction between avoiding injury and bringing aid as the principle factor in determining the morality of the actions available in the third example would be nonsensical. While her critique of using “direct and oblique intention” as the determining factor would still be apt, for those with this irregular intuition, it seems the alternative she provides wouldn't be satisfactory. Then again, perhaps this isn't an intuition many feel the need to appeal to considering how unappealing it is to me to explain how one might possibly begin to justify the view that withholding aid from and directly harming others are morally equivalent. There is also the floodgate of arguments to consider that could have been opened had Foot contested or at least made contestable the moral consideration given to fetuses being equivalent to that given to mothers, but in the interest of brevity and directness, she was probably wise not to.