How are outcomes different when a doula is present?

A doula’s presence can influence a number of outcomes in the process of childbirth, from medical interventions used to the length of time a woman breastfeeds her baby.  It has been shown in numerous studies that the reassuring presence of a knowledgeable support person not only makes the experience more satisfying for women, but also safer, using fewer medical interventions.   My experience is consistent with the research of Klaus, Kennell, and Klaus in Mothering the mother:  How a doula can help you have a shorter, easier and healthier birth (1993).  Their analysis, shown below, showed that there were fewer medical interventions used in the births of women who had a trained doula attending their births:

60% reduction in epidural anesthesia
50% reduction in Caesarian section rate
40% reduction in the use of Pitocin for labor stimulation
40% reduction in forceps-assisted births
25% shorter labor in first-time mothers