What is your definition of 'innocent'? What do you call 'evil'? What do you take 'sinful' to mean? Everyone has different ideas about all three words. But, according to the Bible, sin is every deed, word and thought that clashes with God's holiness and righteousness. Clearly, no new-born baby can be guilty of that! There is a certain innocence attached to them insofar as they are utterly helpless, cannot think, speak, or do anything other that that which helps them survive.
As for being "evil according to the Bible", nobody can quote even one verse in the entire Bible that claims new-born babies are "evil". The Bible does speak about "being conceived in sin" (even though father and mother be married and God-fearing). You have to study the Bible to grasp what that means. It does not mean what you are asking.
That's because 'evil' is not a principle in creation, but is taking God's good gifts to turn into weapons against God. No new-born baby can do that!
However, when we observe that every baby will, sooner or later, start to show signs of sin (observe the 'terrible twos' - screaming, stomping their little feet and throwing tantrums to get their own silly, selfish way); we must admit that, internally, something's wrong. Have they inherited something from their sinful parents? Is there a basic flaw in their human nature that means all babies cannot help but sin, sooner or later, and lose the new-born 'innocence' we all acknowledge at a human level? The Bible explains such matters, but the way most people turn this question into a weapon with which to attack Christians and God is a clue as to where the real evil is to be found.