Assessment of bony pelvis and vaginally assisted deliveries.

Objective. To evaluate whether pelvic measurements have any association with operative vaginal deliveries and the duration of the second stage of the delivery. Study design. A retrospective study of pregnant women at an increased risk of fetal-pelvic disproportion during 2000-2008 in North-Carelian Central Hospital. The mode of the vaginal delivery was chosen to represent the reference standard. The target condition was spontaneous vaginal delivery. Patients were divided into subgroups according to the size of the fetus and also by the parity to evaluate the variability reflecting differences in patient groups. Receiver operating characteristic (ROC) curves were established. Results. A total of 226 participants with fetal cephalic presentation delivered vaginally; of these, 184 women delivered spontaneously, and 42 women required operative vaginal delivery with vacuum extraction. There were no clinically or statistically significant differences between the size of the maternal pelvic outlet and the different modes of delivery types within these subgroups. With respect to the pelvic inlet and outlet, the areas under the curve in ROC were 0.566 with the P value of 0.18 and 95% confidence interval (CI) of 0.465-0.667 and 0.573 (95% CI: 0.484-0.622; P = 0.14). Conclusions. The maternal bony pelvic dimensions exhibited virtually no correlation with the need for operative vaginal deliveries.