You're completely missing the point. A baby which has already been born can be kept alive by ANYONE who is willing to take on the task. A baby which has not yet been born, and is not yet viable, can ONLY be kept alive by the mother -- and if she is unwilling, then it would require government coercion of her to support another "person". That is a VERY dangerous principle, which leads down the slippery slope to full blown socialism. The underpinning of your position is becoming increasingly unsupportable. It will soon evaporate entirely.
It's currently possible to remove a fertilized egg or embryo from the mother and implant it in another woman. I'm not sure the time limit on this but believe it to be three weeks.
"Preemies" are able to survive at earlier and earlier ages. The youngest I've Googled up was 21 weeks.
So the current "window" of "exclusive support" is 18 weeks, and shrinking.
Doctors are at work on artificial wombs.
Besides, the mother exercised her right to "choice" when she performed the act resulting in her pregnancy. After that, I say she's obligated to a third party, the baby.
I've never heard of embryos being transferred and I'm pretty well read up on the subject of assisted reproductive technologies (perhaps it has been done in farm animals, but I'd think with a very low success rate). Once an embryo has implanted -- which is within the first few days after fertilization, and well before a woman would be aware she is pregnant -- it cannot be transferred. If it did become technically feasible to accomplish such transfers, with no more time or discomfort to the pregnant woman than an abortion, then I would agree that it would be reasonable to expect women who wish to terminate their pregnancies to go that route, IF there is a recipient prepared to undertake the pregnancy immediately and at her own expense. At the present time and for the foreseable future, however, this is in the realm of science fiction.