† These authors contributed equally.
X-ray pelvimetry is used for evaluation of pelvic inlet generally to diagnose cephalopelvic disproportion (CPD) or contracted inlet. Cesarean section delivery (C/S) is often performed for labor dystocia without CPD or contracted inlet. We examined whether X-ray pelvimetry is useful to decide on mode of delivery in women with dystocia. A total of 1118 pregnant women received X-ray pelvimetry before or during labor. 205 women with cesarean deliveries for indications except for dystocia were excluded. 913 women undergoing induction/augmentation were retrospectively investigated. Obstetrical and maternal variables were analyzed by univariate, multivariate or ROC analysis. Among 913 women, 37 including three with contracted inlet and seven with CPD, gave birth by C/S, whereas 876 gave birth by vaginal delivery. Low maternal height, older age, small obstetrical conjugate, large weight and infant head size were associated with risk of C/S for dystocia. Multivariate analysis revealed that the obstetrical conjugate was an independent variable for risk of C/S. The area under the ROC curve and the optimal cut-off values, respectively, were as follows: obstetrical conjugate: 0.68 and 11.7 cm (odds ratio = 4.27), transverse diameter: 0.59 and 11.4 cm (odds ratio = 1.82), maternal height: 0.70 and 155.5 cm (odds ratio = 4.33), and maternal weight before pregnancy: 0.55 and 49.7 kg (odds ratio = 1.98). The obstetrical conjugate was an independent variable associated with risk of C/S for dystocia. Maternal height was comparable to the conjugate in term of diagnostic ability. Our data suggested that routine X-ray pelvimetry was not beneficial to identify women at risk of C/S for dystocia.