A mathematical approach to problems of cephalopelvic disproportion at the pelvic inlet

So many problems have been left unsolved by x-ray pelvimetry for the prognostic diagnosis of cephalopelvic disproportion that the clinical usefulness of x-ray pelvimetry has been questioned and a more scientific approach to evaluation of cephalopelvic disproportion has been sought. By unifying various factors that impose problems in cephalopelvic relationships into one index via new mathematical models, we attempted to estimate quantitatively the potential dystocia caused by inlet disproportion. The index is calculated from ten measurements of data obtainable on roentgenograms, and the practical calculations can be readily done with a programmable calculator. The validity of the assumptions used in the mathematical models and the reliability of the developed index were retrospectively analyzed in 300 primiparous women with cephalic presentations. This study suggests that the mathematical index could serve as a useful prognostic guide to the proper management of labor in association with disproportion.