Intrapartum transperineal ultrasound assessment of the fetal head-symphysis pubis distance in the active second stage and the mode of delivery

OC14.05 Intrapartum transperineal ultrasound assessment of the fetal head-symphysis pubis distance in the active second stage and the mode of delivery A. Youssef, E. Maroni, A. Ragusa, G. Salsi, L. Cariello, E. Montaguti, N. Rizzo, G. Pilu, T. Ghi Obstetrics and Gynecology, University of Bologna, Bologna, Italy Objectives: To compare the longitudinal changes of the fetal headsymphysis distance (HSD) as evaluated by three-dimensional (3DUS) Ultrasound in Obstetrics & Gynecology 2012; 40 (Suppl. 1): 1–54 29 22nd World Congress on Ultrasound in Obstetrics and Gynecology Oral communication abstracts intrapartum transperineal ultrasound (ITU) during the active second stage according to the mode of delivery. Methods: A 3DUS ITU volume was acquired in a series of nulliparous women at the beginning of the active second stage (T1) and every 20 minutes thereafter (T2, T3, etc.). Following delivery, all 3DUS volumes were analysed and in each dataset HSD was measured together with angle of progression (AoP) and midline angle (MA). HSD was then compared between women who underwent spontaneous vaginal delivery (Group A) and those who underwent operative delivery (Caesarean delivery and vacuum extraction, Group B). ROC curves were constructed to estimate the accuracy of HSD at different time frames in the prediction of the mode of delivery. Finally, we performed stepwise forward multiple logistic regression analyses to identify independent ITU parameters that have a significant association with the mode of delivery. Results: Among 71 women included in the study, 58 women underwent SVD, 8 were delivered by vacuum extraction and 5 underwent caesarean delivery. When compared with group B, group A had a significantly shorter HSD at T1 (15.76 ± 4.63 vs. 23.00 ± 7.17 mm, P < 0.001), T2 (12.55 ± 3.73 vs. 21.00 ± 6.38 mm, P < 0.001) and T3 (12.05 ± 3.19 vs. 16.38 ± 4.96 mm, P = 0.025). ROC curves revealed an area under the curve ± SE at T1 of 0.810 ± 0.068, at T2 of 0.879 ± 0.071 and T3 of 0.776 ± 0.108. At stepwise forward multiple logistic regressions HSD was identified as the only ITU variable associated with the mode of delivery (the odds ratios (exponential beta) 0.832, 95% CI 772–0.8975). Adding the angle of progression or the midline angle to this model did not yield statistical significance. Conclusions: Fetal head-symphysis pubis distance in the active second stage of labor seems a strong sonographic predictor of the mode of delivery.