Pseudo-Onkelos
Kuroko and the Lamb
Nope, babies are not innocent. Romans 3:23. David has even written several psalms with verses about sinning in his mother's womb. No one is innocent.
How can one have sinned if one has never acted sinfully? Why take these literally when they're found in the psalms? And David speaks only of himself, but why take him literally?
Psalms 51:5 address it, David claims he was sinful from the moment his mother conceived him, and sinful at birth. The psalms is about his sin against God and was written right after he committed adultery. I don't see how else we can interpret it other than literally. The entire song is pretty straight forward.
Regardless man has been cursed with a sinful nature, that of which we inherited from Adam and Eve. I don't know what babies are doing that's sinful before God, either way they had sinned, for everyone has sinned.