I am currently 9 months pregnant. Yay! In order to memorize my baby bump, I shooted pictures with my husband. As I had a professional photo grapher, it was way easy to get good one. Preganancy is not a usual event in your life! Go take pictures!
What I recommand are:
Wear a dress that has one color. The simple dress is the best choice to attract your baby bump without any distraction. I recoommand either white or black.
Use a natural light. Light is a foundation of pictures. The quality light can create beautiful moments with the happiest smiles of soon-to-be mom.