I'm a bit confused, since reading the book and watching the movies and shorts makes me wonder if Rachael was, from the start, able to get pregnant.
Because if she is, then it means the technology and knowledge is already available, so the 2049 part turns (to me) pointless.
And if this was results of evolution, nature, mutation,etc. why there aren't more replicants able to do so (or being already pregnant)?
So the question is was a feature or by chance Rachael capacity to reproduce?