So lets say a homicidal entity from another universe needs a vessel to enter our universe.  So of course an unborn child will be the receptical for that evil presence, and if the mother gives birth to it our universe could end.  Lots of horrible things will happen as our world twists and distorts from the presence of this alien being, and presumably the father of the child will take partin saving our universe. 

BUT, remember, people will be dying left and right and while the alien entity will have a good reason to keep the mother alive and healthy, the father has no such promise.  If the entity tries to keep the father alive at all, it will only be a symbolic gesture, and when it all comes down to it, expect the entity to turn on the father who is somehow immune to most of the weird stuff going on.

Thought Inspired by, but not directly related to: Crescent, horror sci fi podcast.  Good stuff, check it out! http://www.crescentstation.net/