I was on the fence about this issue until I had the huge influx of pregnant mums. I didn't like the thought of doing it, but neither did I criticise those who felt they needed to.
Now I have had to spey does who quite likely were pregnant, although babies could not yet be felt. The ones I could feel I let carry on to term. Incidentally one of these litters died as their young mum wasn't too good at her job
And the other young mum had to be PTS as she prolapsed her bladder
I am now hand rearing her litter. If I had had these two speyed the does would both probably be fine. Whether the babies survive or not now is yet to be seen. But I wouldn't have been willing to do that and the vet said that the point at which they can be felt is the line of whether or not it is safe for the mother, apart from the consideration of the babies.
I am now having to turn rabbits away as I am so full. To let a doe carry an early pregnancy on seems to me to be unfair to those other rabbits out there that need rescue space.
As for abortion in humans, I think that it is a necessary evil. No child should be born if it is not wanted, to a mother incapable of looking after it, as that is a dreadful fate, worse than not being born. But it shouldn't be allowed after 3 months unless the mother will die otherwise. Three months ought to be enough time to make the decision if the woman is well supported, and she should be, including being given the information about how she is likely to feel about it later in life - ie guilty and sad and possibly left childless and heart torn, as well as the information about how difficult it is to bring up a child. Not an easy choice, or decision.