I've come to the conclusion that there's no way that Palpy can't know that Padme is pregnant, especially since she's got scenes with him. "The Emperor knew, as I did, that if Anakin were to have any offspring, they would be a threat to him." - Ben. I'm sure he knows and tries (and probably succeeds) in bumping her off. I just can't see how she could possibly hide her pregnancy from the Dark Lord of the Sith, especially when she's right in front of him.