As much as I hate to be the one to ruin the illusion, I am fairly certain that the first two pics, at minimum, are photoshopped. This girl's expression is COMPLETELY identical between the two, everywhere from the directions her eyes are pointing to the precice shape of her smile. Even if it's a girl that perfectly replicating her own expression, she would at least be looking a different direction as the photographer is in a different position. I would love this to be an adorable young mommy nowhere near ready to have the baby that has made her tummy so huge, but alas, unless someone else has a really compelling argument why I'm wrong, I'm pretty sure the poster of these images used a younger girl's face on an older girl's pregnant body to make her look much more "teen" than she really is.
Not a bad Photoshop though, all things considered. And that is a beautiful bump on a very short, skinny girl either way.