Any reason, no restrictions.
In practice, restrictions usually wind up doing nothing but putting women at risk. We have examples of nations that have no restrictions, and in general, the curve of when and why women get abortions looks exactly the same as it does in the US.
With one important difference.
Lower mortality rates for women.
Because they are able to get advised abortions WHEN they're advised, rather than being forced to wait for it to become a life-threatening emergency. Because that is the reason women get very late abortions.
Elective abortions take place earlier and earlier, as both our detection methods and abortion choices get more sophisticated (very early abortions used to be impossible before medical abortion; the surgeon couldn't see well enough to find a "week 5" embryo and thus couldn't perform the abortion until later, but this is no longer an issue with the medication route). Women want to do them sooner if they can.
So restrictions (apart from total ban) only become an issue with late abortions, which are often medical cases. And the later you go, the more true that is.
There is no evidence this would change. Very late abortions are, after all, very dangerous, very slow, and very unpleasant. And even when given the option of doing them for other reasons, women simply don't. If at all possible, they prefer to get a C-section. And that solves the issue just as well, the issue being that the woman needs to be able to preserve herself -- and a C-section gets the job done in these sorts of situations.
For me, that is the concern. Either an abortion or a C-section is a solution to the issue of a woman needing to be able to preserve herself. It just happens to be that at some points, a C-section isn't possible, or isn't as safe. And in either of those situations, abortion needs to be an accessible choice.
Of course, some women choose the more dangerous option anyway, in hope of finding better odds of preserving the fetus. That's also a choice they should have access to make.
