I think the point is that it can't continue outside her body without her going through a procedure - childbirth - which she may not wish to go through. And that's entirely her decision. She is no more required to give birth to "save" that life than she would be to donate a kidney to save a life.
> but I was irritated by the blanket statement (not coincidentally made by
> males) that a foetus can be killed whenever and for the hell of it.
I have heard many women make essentially the same statement. I would have no difficulty making the same statement, provided we are talking about the woman who is carrying the fetus being the one making the decision to kill it.