My scientific opinion, and I'm no expert, is that the biochemical and physical interactions between a mother and an unborn infant are one hell of a lot more complex that the simple functions of providing oxygen and nutrients. I don't think this is going to work. I think it's going to be harder even than an artificial liver, and you can ask a biologist how hard that would be.

My personal opinion, having been with my wife through two pregnancies, is that there is a strong physical and emotional bond far beyond chemicals. To a great extent, the baby ate what she ate, heard what she heard, felt what she felt, and somehow knew that there was someone out there that would take care of him/her. To watch a pregnant mother talking to her baby, or soothing it out of a kicking fit or a case of hiccups, is something marvelous.

This technology might be appropriate to save the life of an infant whose mother was dying or something, although it seems that the embryo must be implanted there in the first place for it to work at all.

Other than that, what possible justification could one have for using such a system? I can't think of any.