Action cropping takes a while, I gotta say.
So the big reveal - no one can hurt me, Mackers says, except one not born of a woman. Macduff replies, done - I was born by Caesarian delivery, which was generally (and we can assume as much here) fatal for the mother. Born of a corpse; born to make one of Macbeth.
These days, with the advances in medical science, they figured out caesarean births and the chances of a woman dying from a caesarean birth are much lower. Of course, in Macbeth's time things were a much greater risk for the mother! :D
Heh. Gotta love Shakespeare, doing the ol' "prophecy twist" centuries before J. K. Rowling!
Ok, so the Greeks were doing it centuries before Shakespeare...