When rounded mama is making intentional decisions, she receives better care than if she numbly does what she's told I think. She is able to tailor the expert advice to herself and her baby. She has instincts and understanding that a medical professional can't know about her unique pregnancy. The happy ideal is harmonious respect for the mother's capability and also the professional's expertise.
Perhaps even more significant, when mama is in charge, she takes better care of herself and baby. She gets that what she eats matters, what she does matters, and what she feels matters. She is the only one who can eat right, do right, and feel right for her developing fetus. Her trust for wellness rests in this body of hers designed to bring life. She appreciates others assisting her to grow, labor, and deliver her baby.
What's more, a woman in charge (not the same as being in control) surrenders to life flowing through her. She is in awe of her body and this new person given to her care. Though frightening, she welcomes the terrific waves of energy carrying life forward. She chooses an intervention because she knows it too will assist her. She trusts, and is well. She gives thanks for every privileged moment holding new life.
More info? Midwife Thinking is a tremendous place to start.