“It can also be comforting to both the father and mother to know that they have an ally, someone who helps birthing families often, a woman who can help them get more of the kind of birth they are hoping for….
….Frequently, couples state that they were much more satisfied with the births in which their doula was present. Couples who hire a doula once will often choose to hire a doula for the births of all of the rest of their children.” Wise Childbearing, What You’ll Want to Know as You Make Your Birth Choices, Your Support Team (pgs 191-198)
Here is great information on continuous labor support: http://evidencebasedbirth.com/why-wouldnt-you-hire-a-doula/ .
What I like best is the conceptual model toward the end of the article. Very well-done!