French obstetrician Michel Odent puts forward the very interesting question of what the basic needs are of labouring women[1]. In order to answer this question he looks to physiological concepts such as adrenaline-oxytocin antagonism and the concept of neocortical inhibition.
Adrenaline-oxytocin antagonism
The mechanism of adrenaline-oxytocin antagonism means that mammals (including humans) cannot release oxytocin at the same time as they release hormones of the adrenaline family.