'Women with companions (such as doulas) who were not on the hospital staff and were not the woman’s partner, friend or relative experienced the greatest - and quite impressive - benefits.'

http://www.childbirthconnection.org/giving-birth/labor-support/research-evidence/

'Yes, doulas are awesome. But we’re not awesome because we have the potential to lower the cesarean rate, but because we provide something no one else can: nonjudgmental emotional support.'

http://www.columbusbirth.com/the-use-of-research-to-discuss-the-benefits-of-doula-support/