I think you can shorten the gown by raising the hem up. I haven't tried it because I love the long drapey look. You might try PM'ing someone in the stores that has images of Pregnant women and ask what they did for clothing.

"It is good to see ourselves as others see us. Try as we may, we are never
able to know ourselves fully as we are, especially the evil side of us.
This we can do only if we are not angry with our critics but will take in good
heart whatever they might have to say." - Ghandi