The predictability of labor outcome from a comparison of birth weight and x-ray pelvimetry.

The value of x-ray pelvimetry in labor has recently been questioned by many, although few morphometric data on the fetopelvic relationship have been presented. Fifty-one women who had dysfunctional labor, in whom both x-ray pelvimetry and oxytocin were used during clinical management, were studied. Twenty-seven were delivered by cesarean section, while 24 were delivered vaginally. Regression equations were developed for multiple pelvic indices versus birth weight. The analysis revealed no differences between the vaginal group and the cesarean section group. The design of this study suggests that the variables of pelvic measurements and birth weight do not provide a predictive tool for delivery outcome. The approximately 15% margin of dimensional differences between a successful outcome and a failed outcome is too small to be detected by current diagnostic methods.