PELVIMETRY BY MAGNETIC-RESONANCE-IMAGING AS A DIAGNOSTIC-TOOL TO EVALUATE DYSTOCIA

Objective: To test the clinical value of magnetic resonance imaging (M RI) pelvimetry for the diagnosis of cephalopelvic disproportion. Metho ds: All deliveries from January 1993 through December 1994 were review ed to identify 42 nulliparas at term with vertex presentation and cesa rean delivery due to dystocia. Complete data were available for 41 wom en, and subjects were divided into the following two subgroups, accord ing to clinical data: cephalopelvic disproportion'' (n = 28) and ''fai lure to progress'' (n = 13). Ten nulliparous women with uncomplicated vaginal delivery served as controls. Pelvimetry data from postpartum M RI were correlated with fetal and neonatal dimensions to evaluate vari ous criteria for the diagnosis of cephalopelvic disproportion. Results : Comparing both the fetal head volume derived from antepartum ultraso und assessment and the neonatal head volume (postpartum measurement) w ith maternal pelvic capacity determined by MRI, cephalopelvic dispropo rtion (head volume exceeding pelvic capacity) indicated that 25 and 27 , respectively, of the 28 women had been clinically diagnosed correctl y with cephalopelvic disproportion, corresponding to sensitivities of 89% and 96%, respectively. Fetal head volume was not larger than pelvi c capacity in any of the women in the control group. In seven of the 1 3 women diagnosed as ''failure to progress,'' the fetal head volume ex ceeded the pelvic capacity. Conclusion: A fetal head volume estimate e xceeding MRI-measured pelvic capacity is a frequent finding in nullipa ras with cesarean birth due to cephalopelvic disproportion. An appropr iate prospective study to determine the benefits of an antepartum diag nosis of cephalopelvic disproportion in high-risk nulliparas is warran ted. (C) 1997 by The American College of Obstetricians and Gynecologis ts.