In my last trimester it became my primary seat around the house, just sitting still on it is a work out for your back, and rolling your hips around as you sit can help to open up your hips in preparation for labor. But, that is not the end of it! My birth plan was to stay home for as long as possible and I spent a great deal of that time on my knees with my upper body draped over the ball breathing through my contractions (by the way, I was 9 cm when I arrived at the hospital, just saying).
Still that is not the end of what this ball can do for a new mom! I am using it again as a seat around the house to help strengthen my back, there are lots of resources for using a ball as a prop to workout at home. Best of all, the baby uses this ball too! We use the ball for supported tummy time, as pictured, (once his cord stump has fallen off). My child also loves using the ball for comfort, I will hold him at my chest, looking in his eyes and bonding, while gently bouncing on the ball - he nearly always falls asleep in just a few minutes, and this is his favorite way to relax when he is fussy.
Find a ball and buy it, you will find so many ways to use it!
What did you find indispensable while pregnant or with a newborn?