I did some pregnant ladies using the Morphing Fantasy Dress. It's not a night gown, but the people in the MSN groups I'm in loved them. Also, if you are looking for some really great poses for a pregnant woman, check out Antje's store. She has some gorgeous poses that come with facial expressions. If you are looking to make just any clothing fit a pregnant woman, I do recommend Wardrobe Wizard. You can analyze it from the base figure, then inject the morphs and then fit the clothing to the new morphed figure. It's a great asset to poser.

"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