[Pelvic torque as a physiological mechanism in labor]

The author proposes to direct the attention of obstetricians to certain features of the physiological birth process to which little consideration has been given. These features have been unjustly neglected, because after their careful and in-depth analysis, the somewhat disconcerting suspicion is raised that the term "birth canal", as traditionally perceived and explained in obstetrical treatises, is totally inappropriate. The author would in fact like to provoke discussion regarding the suitableness of substituting the usual didactic expression "birth canal" with the new term "pelvic press", which is more to the point in evidencing an important physiological action, similar to that of a hydraulic press, which, in his opinion, starts between the bony walls of the pelvis during the second stage of labor. The author maintains that the functional role of the "pelvic press" consist in the multiplication of part of the expulsive forces set off by the uterus and the abdominal musculature to determine rotation movements of the presenting part, and, above all, to serve as a most valid protective action for the fetus throughout the entire birth process.