Assessment of dystocia pelvis by ultrasound pelvimetry

Following successful preceding studies, a quantitative analysis of the female pelvic cavity was made using contact compound scanning procedures. The subjects were seventy-seven, 3 day postpartum women and ultrasonic tomograms were obtained concerning the five pelvic transections in each individual. For the quantitative analysis, variables of binary digits were used. Such were based on the standard of "normopelvis" in the polar coordinate system plus the external criteria, normal progress of labor, protraction and arrest disorders. Characteristics of the dystocia pelvis included an abnormal side wall of the small pelvis as well as an increased resistance of the muscles of the pelvic floor. The efficiency of the discrimination was greatest when those variables were adopted from each transection (78.3%). Arrest disorders could be clearly distinguished from the normal cases, however, cases of protraction disorder presented more difficulty as the distribution was wide between normal and the arrest disorder. Here, the pelvic floor muscles contribute significantly. The newly developed numerical system should make feasible an early prediction of dystocia, assist in screening processes and pave the way for accurate assessments of the interaction of anatomical factors related to the mechanics and processes of labor.