I’m an amatuer too, so let’s see if we can work this out. IIRC, there are 4 questions that must be satisfied for double effect to apply.
- Is the end a moral good? (i.e. we’d sure like to save at least ONE of the lives at risk in the case of ectopic pregnancy)
- Is the direct action morally good or at least innately morally neutral? (i.e. you can’t take a pill to poison an unborn child, but you can surgically removed a diseased section of fallopian tube in an ectopic pregnancy)
- Is the morally bad side effect unintended and unavoidable? If there are other options, double effect doesn’t apply.
- Is the proportionate impact of the morally good end larger than the proportionately bad impact of the indirect side effect? (i.e. check if the ‘do nothing’ option does less harm in the end.)
IIRC, you have to satisfy all four, not just one or even 3 of 4. All of them.
So to answer your question, if the mother (hypothetically) had a condition that required surgery or medication in order to save her life and that action had a high likelyhood of causing the death of the child and the near certain outcome of doing nothing would be the death of both of them, D.E. may apply. But only if the surgery or medication had a morally good direct effect (not just end). If the direct purpose is to kill the child in order to (for example) shut down the hormone imbalance about to kill the mother, it fails the test. This stuff gets pretty hairy, but the alternative of going with the gut is worse.