Kudos for trying to create a non-cliche maternity shot. As a standalone image I think it has its merits (I do like Derrel's suggested crop).
I think it falls short as a maternity shot however. Maybe I was biased by the post's title, but since the room, though dark, isn't particularly dirty I thought that maybe what made it a "dirty" shot was that she was not wearing anything besides the shirt. And in trying to decide that, I realized that from this angle I couldn't tell if she was pregnant or just had a large belly hanging down on top of her legs (no disrespect meant). Between the seated pose (removing the bottom curve of the belly bump) and the shirt's coverage (removing the top curve of the belly bump), I'm not getting enough "maternity" out of it.
When shooting maternity images, I first realize that my subject isn't really the mother-to-be, it's the belly. Visualize angles and lighting which show off the belly how you want it seen. Then you can tweak the rest of the shot (the rest of her body position, her expression, the location) to get the final product you want.
She is daring, both to pose for this kind of shot and to let you put it online. Perhaps she will be up for another session...