This is a bit horrifying to me. Babies are quite familiar with their mothers' voices by the time they are born, among other influences; would we also attempt to artificially simulate that sort of pre-birth bonding?
Whales have the right body temperature. There is enough room to do dozens of babies at once.
Cows are close enough. A cow can probably handle a half dozen babies.
https://en.wikipedia.org/wiki/Interspecific_pregnancy#Causes...
We can suppress the immune response, one way or another. If the animal is unable to clear the placenta after the birth, we lose the animal, but we still get a baby.