Intrapartum translabial ultrasound (ITU):: sonographic landmarks and correlation with successful vacuum extraction

Objective: Having studied intrapartum translabial ultrasound (ITU) to define easily obtainable sonograpbic criteria during maternal pushing, we used it dynamically immediately before vacuum extraction to determine its use in predicting successful operative vaginal delivery. Methods In a pilot study, maternal and fetal landmarks were determined sonographically during maternal pushing from a mid-sagittal translabial insonation using a curved array transducer in women delivering singleton fetuses in cephalic presentation spontaneously. With this transducer placed infrapubically ('infrapubic plane), easily obtainable landmarks and signs were: (i) the 'infrapubic line, perpendicular to the long axis of the pubic joint and extending dorsally from its inferior margin in a mid-sagittal plane, (ii) the widest fetal bead diameter and its movement with regard to the infrapubic line during pushing, and (iii) the 'bead direction' with respect to the long axis of the symphysis. A three-dimensional reconstruction from a computed tomographic (CT) dataset of a normal female pelvis was then used to quantify accurately the spatial relationship between the infrapubic line and the anatomical landmarks. Finally, 20 pregnant women in spontaneous term labor with normal singleton fetuses in cephalic presentation and clinical indication for vacuum extraction were studied by ITU immediately before operative vaginal delivery. Results CT reconstruction demonstrated the infrapubic line to be 3 cm cranial to the parallel interspinous plane. Eleven of the 20 vacuum deliveries with the 'bead-up' sign (bead pointing ventrally) and objective descent of the fetal bead below the infrapubic line, both noted at the height of pushing, resulted in successful (simple' or 'moderately difficult') operative delivery. Lack of descent or lack of passage below the infrapubic line and horizontal or downward bead direction were poor prognostic signs. Conclusions ITU provides objective information on the dynamics of the second stage of labor, bead station and bead direction. ITU may be used to assess the prognosis for operative vaginal delivery. Copyright (c) 2006 IS UOG. Published by John Wiley & Sons, Ltd.