[Mechanism of labor with delayed membrane rupture]

The Authors supports the thesis that physiological labour in which the rupture of membranes is sudden and spontaneous, and labour in which the fetus is "hooded" and the rupture of the membranes is delayed and usually performed artificially, are both regulated by the same type of mechanical phenomenon. The arguments put forward to demonstrate the validity of this thesis contain important deviations from the traditional interpretation of the mechanics of physiological labour. In fact, the interpretation of labour in which the rupture of membranes is delayed must take into account mechanical phenomena based almost entirely on physical laws of fluids, whereas in the traditional interpretation of the mechanics of physiological labour these hydraulic-type phenomena are not recognised as playing a role. In the Author's opinion, this differences of interpretation has no reason to exist since the hydromechanical type phenomena observed in labour with delayed rupture of the membranes can also be found in physiological labour during which they perform functions of primary importance. For example, the onset of ninus with its multiple and important consequences, the indirect interaction of the fetus in the birth process throught the amniotic liquid which is its ring-like annex, the internal and external rotating mechanism of fetal presentation, and above all the providential protective or self-protective action of the fetus during the process of birth.