After residents of a small town are quarantine by the military, the adult male residents begin to show signs of pregnancy – with something that might not be human.

Sounds suspiciously like "The Midwich Cuckoos" which was made into a movie called "Village of the Damned" I think. Not a problem if you can tell a different story, just be aware of the similarity.

Presume some kind of thriller here but as you've acknowledged it is not much more than a premise at this point. Good luck with it.

That being said, it is a great premise. Adding a compelling lead character will just add to what you have already written.

Thanks everyone.

Yep, this is a premise not a logline. I need to think about what angle to take to make it more specific.

As Richiev said, it is a great setting but not a logline. You gave us the opening or the first 15 to 20 minutes of the movie, but a logline is supposed to give you Act I and II.
Who is the protagonist? The infertile wife of one those men, one man, somebody sent to investigate?
What is she going to do? Defend the baby against the army or try to kill it?
Who is the enemy? The US Army afraid of the alien or the aliens themselves?
What are the genre and sub genre? Science fiction drama, romantic horror, Action Science fiction?

When a state-wide quarantine is enacted, the male residents of a small town become cocoons for invading extraterrestrials.

This is the second logline you've described a situation but haven't given us a lead character or a goal.