If you are easily disturbed please don't read this. I'm serious.
Well, see, the aliens lay their eggs inside your esophagus. You are probably unconcious at the time, and while you sleep the eggs slide down your throat to sit in your stomach. THey grow bigger and bigger making you look pregnant. All of a sudden, the eggs hatch and leap out of your stomach, killing you instantly in a spray of blood, gore, and green slime. Yay for baby aliens!