I think there's two schools of thought (because this move has schools of thought, yes indeed) that I've heard on the baby Satan is holding. Mel made a comment which I will post also.
Number 1 (which is what I thought when I saw it)
The deformed baby is making a mockary of the classic Madonna and Child images.
The second is that the baby is the anti-christ who will battle Christ at the second coming . . .as in Revalations. (errrr I didn't see this at all but - hey!)
It's evil distorting what's good. What is more tender and beautiful than a mother and a child? So the Devil takes that and distorts it just a little bit. Instead of a normal mother and child you have an androgynous figure holding a 40-year-old 'baby' with hair on his back. It is weird, it is shocking, it's almost too much—just like turning Jesus over to continue scourging him on his chest is shocking and almost too much, which is the exact moment when this appearance of the Devil and the baby takes place
Make up your own mind, however. :wink: