I came across this great article on doulas: Why hire a doula- 5 myths debunked.
Full of great information about what a doula does and does not do. For example, a doula does not interfere with the bond between you and your partner. She does facilitate his involvement. A doula can not "save" you from a high-intervention doctor or hospital. She can encourage you to advocate for yourself and to have important conversations with your care-provider before you are in labor. I recommend you read the whole article. And then hire me of course :)