X-ray pelvimetry: helpful or harmful?

This study was performed (1) to clarify the usefulness of x-ray pelvimetry in diagnosing cephalopelvic disproportion (CPD), particularly in patients with abnormal labor, and (2) to examine the association between infant birthweight and mode of delivery. The subjects were 100 consecutive patients who underwent x-ray pelvimetry. A retrospective chart review was done to collect demographic data and evaluate Friedman labor curves. Radiologic dimensions were tabulated for anteroposterior diameter, transverse diameter, and summation plane values of both inlet and midpelvic planes. Average pelvimetric values for subjects delivered vaginally and those delivered abdominally were compared, and Hotelling's T2 analyses were conducted to determine whether the differences were statistically significant. Average birthweights of infants born to women in cesarean section and vaginal delivery groups were also compared, with t tests conducted to determine statistical significance. Results showed that even in a select group of patients in abnormal labor with the highest probability of CPD--a condition it was believed x-ray pelvimetry could diagnose--no significant difference in bony pelvic dimensions existed between vaginal and cesarean delivered patients. The cesarean group did, however, deliver significantly heavier infants. The results question the usefulness of x-ray pelvimetry in diagnosing CPD.