The word, "doula," comes from the ancient Greece a word for the most important female slave or servant in an ancient Greek household, the woman who probably helped the lady of the house through her childbearing.

In our days it's meaning refers to "A woman experienced in childbirth who provides continuous physical, emotional, and informational support to the mother before, during and just after childbirth." (Klaus, Kennell and Klaus, Mothering the Mother)

Or, you may call her  a 'Birth Angel"

Doula is then a childbearing-wise female, who selflessly nurtures and protects the mother/birthing couple throughout the process of birthing and postpartum.

Even  our conservative 'left brained' medicine now recognizes the marvelous role of a 'doula' during birth: Numerous studies have shown that a mere continuous presence of another woman during birthing shortens the duration of labor lessens the intensity of contractions and the need for interventions. It is as if just the mere physical presence of a kindred spirit would give the laboring mother a source of strength and optimism, acknowledgment that 'everything is  all right', the necessary element for surrendering the marvelous force of birth.  With  a Doula - a woman specially prepared for nurturing the birthing mother/couple, these outcomes  may be, of course, even more pronounced.