The standard Catholic view of tubal pregnancy is that it is permissible to remove the tube with the child. The idea seems to be that the danger to the mother comes from the potential rupture of the tube, and hence removal of the tube is removal of that which poses the danger, and the death of the child is a non-intended side-effect, with the action justified by double effect. I’ve always been queasy about this reasoning, but I now have two related analogies that make me feel better about this.
Case 1: There are two astronauts on a spaceship, with no oxygen left in the air. The astronauts are wearing spacesuits with oxygen tanks. The oxygen tanks are sufficient for the astronauts to survive until they get home: 50% of the oxygen can be expected to be used up before getting home. However, one of the tanks is rigged by a malefactor with an explosive device such that if more than 20% of the oxygen is used, it will explode, killing both astronauts. The astronaut wearing that particular spacesuit is unconscious and cannot be consulted. It is not feasible to disarm the bomb or to swap tanks. The conscious astronaut removes the explosive tank from the other astronaut’s space suit and throws it into space, knowing that this will result in the unconscious astronaut dying from lack of oxygen. The intention, however, is to remove the item that will dangerously rupture if it is left in place. It is not the intention to kill the other astronaut. This is true even though it is the other astronaut’s breathing that would trigger the tank’s explosion.
The proximate source of the danger is the oxygen tank. But the more distant source is the breathing. It seems very plausible that it makes a moral difference whether the conscious astronaut shoots the unconscious astronaut to stop their breathing (wrong) or removes their tank to expel the danger (right action). This seems a legitimate case of double effect reasoning.
Case 2: Much as in Case 1, but (a) there is intense radiation outside the spaceship’s shielding, so that getting pushed into space even while wearing a spacesuit on will be fatal, and (b) there is no way to separate the tank from the astronaut. Thus, the other astronaut picks up the explosive tank, and throws it far into space. The tank is connected to the unconscious astronaut, so the unconscious astronaut flies out with the tank, and is killed by radiation. The tank never explodes, because the oxygen doesn't get depleted
Again, this seems a perfectly legitimate case of double effect reasoning.
What about the alternative of removing the child from the tube, which orthodox Catholic ethicists tend to reject (unless done in the hope reattaching in the correct place)? Well, the child is connected to the tube via a placenta. The placenta is to a large degree an organ of the child. As I understand it, removal of the child from the tube would require intentionally cutting the placenta, in a way that is fatal to the child. This directly fatal intervention seems akin to slicing the astronaut to remove them from the suit. This seems harder to justify.
