Pelvimetry revisited: analyzing cephalopelvic disproportion

The objective of this study was to assess the clinical value of pelvimetry to predict dystocia due to cephalopelvic disproportion. 63 patients who had received an abdominal CT scan postpartum were included. Pelvimetry was performed retrospectively with these datasets on a 3D workstation; there were no CT examinations performed solely for pelvimetry, and there was no radiation exposure for study purposes. Patients were divided into three groups by the course of birth, i.e. normal vaginal delivery (A), dystocia due to cephalopelvic disproportion (B) and other patients (C). Previously described methods were evaluated for their accuracy in diagnosing cephalopelvic disproportion. The pelvimetric parameters did not show significant differences between groups A (n=20) and B (n=20) except for the sagittal mid-pelvic diameter (q) with 12.7+/-0.6 cm vs. 11.9+/-0.6 cm (p=0.0001). The ROC analysis of the previously described methods showed areas under the curve between 0.50 and 0.67. The ROC curves for q had an area of 0.88, providing 85% sensitivity with 85% specificity. In conclusion, the sagittal mid-pelvic diameter shows potential to detect cephalopelvic disproportion with acceptable accuracy. With the information gained on the CT data, a prospective trial based on MR imaging can be set up to validate the diagnostic accuracy.