http://www.huffingtonpost.com/well-rounded-ny/why-a-birthing-ball-can-h_b_10724180.html
The mere idea of sitting on an unsteady birthing ball during labor (and even pregnancy!) can be daunting. But when used properly, birthing balls, also known as exercise and fitness balls) are excellent tools to sustain a healthy pregnancy and successful labor. Indeed, birthing ball exercises can give you the strength and stability that you need to speed up dilation, move baby down into the pelvis, and even manage labor and delivery pain. What’s more, birthing balls are affordable, effective and versatile (you can use them well after birth to help with postpartum pain and breastfeeding, and children tend to think they’re great fun to play with), and you can involve your partner, doula or friend depending on where you choose to deliver. It’s no wonder, then, that so many midwives and birth doulas (myself included) recommend them to their clients.
(Click link above to read on Huffingtonpost.com)