Starring: A Predator, a whole stack of Aliens and various beautiful people waiting around to be lunch.
Story: A Predator spaceship crashes on Earth and some Alien specimens escape near a small American town. Another Predator arrives to clean up the mess and keep it all secret. Lots of people get minced.
Comments: Aliens and Predators fighting each other should be the best thing ever.
It's not. It's mainly dark and confusing and not very involving.
The antics of the humans trying to get out the way are more interesting but are relatively indistinguishable from the antics of the humans trying to get out of the way of vampires, zombies and giant lizards in a score of other films... apart from the bit in the maternity ward - that's probably worth skipping if you've got a new arrival due any time soon...
Conclusion: A film you've seen a dozen times before but with the addition of everyone's two favourite psychotic extra-terrestrial species. Could be worse. (Have you seen Alien Resurrection, for instance?)
Pregnant women: Several.
Scenes in which the housedad doesn't get eaten: Two.
Life lesson: If you're going to stand next to a window and say to a child, "Look! See! No monsters," remember to at least glance out the window first.