A labouring woman releases hormones to enable her to relieve pain and to deliver her baby. The glands that control the release of these hormones are the hypothalamus and the pituitary gland. These hormones are Oxytocin and Endorphins.
We also understand that inhibitions originate in the “new brain” (the part of the brain which is highly developed among humans, the intellect or thinking brain) This is called the new cortex or the neocortex.
When woman is giving birth by herself, without any medication or interventions, there is a time when she cuts herself from our world as if she is going to another planet and acts in a way in which she wouldn't dare to in our society for example shouting or swearing. She can find herself in unexpected postures and making unexpected noises, this means that she is reducing the control by the neocortex. The reduction of the neocortical activity is the most important aspect of birth physiology as this effects the release of oxytocin and endorphins.
Therefore protecting the labouring woman from any sort of stimulation of her neocortex is highly important. The neocortex can be stimulated by the following; language, bright light, being observed and feeling insecure (this will release adrenaline)
Oxytocin = Excelorator, hormone of love
Endorphins = Natural pain relief
Adrenaline = Brakes

Diagram used with permission and copyright owned by Nurturing Birth