" there was one other important trait that would prove to be problematic for the breeding interests of the gods: Nephilim were large, very large. A mature Naphil could reach heights of seven, eight or even nine cubits tall. The Nephilim were giants. The fetus therefore was manifestly huge and tended to stretch a woman’s womb cavity to its limits. For this reason, a Naphil could not be born in a human way. It would have to rip its way out of its mother, killing her in the process. This was all very natural for its kind, since the dead mother would be the newborn’s first meal. "

― Brian Godawa , Enoch Primordial (Chronicles of the Nephilim #2)