Uterine work in parturition.
This  paper presents a theoretical analysis relating work expended by the uterus to the synergistic relationship between intrauterine pressure (IUP) and cervical dilatation (CD). By utilizing a geometrical model for the fetal presenting part which is assumed to be in contact with the cervix, the changes in internal volume of the uterus with each contraction can be shown to be functionally related to cervical dilatation. Thus work, expressed in terms of foot-pounds, can be calculated using the integral of pressure times incremental volume. By simulating intrauterine pressure and cervical dilatation with continuous analytical wave forms, the alterations required in uterine work to dilate the cervix are calculated for various wave-form aberrations which are seen in clinical situations. The wave-form aberrations are applied to an elastic cervical model as well as a viscoelastic model. Using the principles of thermodynamics the areas of the fetouterine complex which absorb the work generated by the contractions are defined. It is shown that the efficiency of the contractions to dilate the cervix can be calculated by evaluating the work expended in these various areas of energy absorption. The purpose of this paper is to present the theory upon which clinical findings in obstetrics can be based so that conclusions drawn will be technically sound.
D002584:Cervix Uteri / Q000502:physiology; D005260:Female; D006801:Humans; D007743:Labor, Obstetric; D008954:Models, Biological; D011247:Pregnancy; D011312:Pressure; D014599:Uterus / Q000502:physiology*