One time I was pregnant. There were some simple things that I really wanted from my partner but at the time, I was too emotional to ask for them in a constructive way. Being a parent is a radical experience, and the starting point is the pregnant part. If you can provide an environment that is comfortable to your pregnant partner, the pregnancy, the birth, and the first months of insanity can be greatly improved. I believe that a pregnant woman's needs are totally within the scope of what you can do.
Step 1: Take notice of the amazing power of her body
Most everyone wants their work to be appreciated, especially in relationships. When someone is working hard, it makes the experience more enjoyable to know that it is not in vain. Your lady is creating a human being without even knowing what she is doing. The baby is being made from parts of her body. It's totally insane and powerful, and if just once a day, you let her know that her body is amazing and doing a good job, you will make her happier.