If you haven't already, you might want to check out Carol Clover's
chapter on the possession film (Ch. 2, "Opening Up") in _Men, Women and
Chainsaws_, where she discusses The Exorcist and other films.  Also,
Vivian Sobchack's "Child/Alien/Father: Patriarchal Crisis and Generic
Exchange" in Camera Obscura 15 (1986) might be useful.
Additional films that come to mind:  Audrey Rose (1977), The Godsend
(Britain, 1979), and, saving the best for last, It's Alive (1974) about
the attack of the killer newborn, and that film's demon spawn, It Lives
Again (78) and Island of the Alive (86).
have fun!
Susan Courtney