"Because she wants to" and "up to a stage in development" are the "certain circumstances" which currently apply in the USA. So abortion on a woman who did not consent, or where the "certain stage" has been reached would be illegal.

And in other countries different "certain circumstances" apply. For example in China the consent of the mother can be dispensed with, I understand.

Nerd's science-fiction situation in which it would be possible for an aborted embryo or fetus to survive by being placed in the womb of another women who wished this to happen, rather than in an incubator or whatever is interesting, but not at present practical.

Quite what would be the accepted ethics in such a situation is as yet totally unclear. I would think that a very good case could be made for saying that the developing human being involved would have a right to be enabled to continue his or her development, if that option was available.

Once again, to suggest that at any stage one human being is the property of another human being is not acceptable.