Everyone keeps posting that Zelena wants the baby so it can be her saviour, but I keep coming back to what the show has said several times. She is looking for the one thing that Rumple most wanted, but could never have. To me that means that Zelena is looking for a true and loving family.
Perhaps her goal is to weasel her way into the royal family. Or maybe to earn Regina's respect and love, then, once welcomed to the fold, she will be the baby's step-aunt.
Also, I don't think she put anything in the OJ. It's just an old midwives trick (no pun intended).
I am seeing the WoO tropes in Rumple being the scare crow and Charming as the cowardly lion, but I don't think Hook is the tin man. I see that role as being Zelena. Now, who's the Wizard who's Dorothy? I have my theory on that, but I'll save it for now.