I think there is a difference between a woman choosing to end the pregnancy (ie determining what happens to her body), and choosing to end the life of the fetus.
If a woman at 12w pregnant decides to end the pregnant, the fetus dies. This question doesn't arise.
If a woman at 35w pregnant decides to end the pregnancy, the only way that fetus dies, is if it is specifically killed. As it's not being done to the mums body, and the pregnancy is ended anyway, I'm not sure why she should have the deciding say on whether it lives or dies, especially if there are others willing to support it (dad, family etc).
And then there's that gray period between about 21w and 30w where there is a glimmer of survival, to an almost certainly of survival, but only with support.
I guess personally, if the baby has a reasonable chance of survival (so day from about 24w) then the woman's choice is to end the pregnancy, not the fetus, and if it survives birth, then it should be supported the same way as any other fetus born of that gestation. I'm not sure how ethically, for example, in adjacent operating theatres it's ok to recusitate and support a baby born at 23 weeks, and next door perform (non tfmr) abortive surgery on a baby of identical gestation. One is treated as a baby, the other not. One given a funeral, the other not.
An exception should be created for where a baby will die shortly after birth due to disability, or be very disabled and have little quality of life, but let's call it what it is - compassionate euthanasia to stop a child being brought into the world to suffer.