Objectives
To assess the feasibility and reproducibility of measuring fetal head station and descent during labor using transperineal ultrasound (TPU) imaging, to compare the evaluation of fetal station through digital examinations with concurrent TPU assessments, and to assess its utility in distinguishing patients whose pregnancy will result in spontaneous vaginal delivery from those who will require operative vaginal delivery or Cesarean section for failure to progress.

Methods
TPU and digital examinations were performed in 88 term laboring patients with a singleton fetus in cephalic presentation. Using TPU imaging, head descent was quantified by measuring the angle between the long axis of the pubic symphysis and a line extending from its most inferior portion tangentially to the fetal skull. Intraobserver and interobserver variability were calculated using variance component analysis. TPU imaging was used to measure the angle of head descent during the second stage of labor in 23 of the women.

Results
Analysis of replicated measurements on 75 subjects, by the same observer at approximately the same time, yielded an average SD (intraobserver variability) of approximately 2.9° for the measurement of angle of head descent on TPU examination. A separate variance component analysis on a subset of 15 assessments for which measurements were repeated by a second observer, with two to four replicate measurements obtained by each, yielded an interobserver error estimate of 1.24°. A significant linear association was found between clinical digital assessments and measurement of angle of head descent by TPU examination (P < 0.001). An angle of at least 120° measured during the second stage of labor was always associated with subsequent spontaneous vaginal delivery. In six pregnancies ending in Cesarean section the mean angle of descent measured at last TPU examination was only 108°.

Conclusions
The angle of head descent measured by TPU imaging provides an objective, accurate and reproducible means for assessing descent of the fetal head during labor. Copyright © 2009 ISUOG. Published by John Wiley & Sons, Ltd.

https://obgyn.onlinelibrary.wiley.com/doi/pdf/10.1002/uog.6329

A new method to assess fetal head descent in labor with transperineal ultrasound.

PURPOSE AND SCOPE The purpose of these Guidelines is to review the published techniques of ultrasound in labor and their practical applications, to summarize the level of evidence regarding the use of ultrasound in labor and to provide guidance to practitioners on when ultrasound in labor is clinically indicated and how the sonographic findings may affect labor management We do not imply or suggest that ultrasound in labor is a necessary standard of care

ISUOG Practice Guidelines: intrapartum ultrasound.

Objectives

To compare the angle of progression on transperineal ultrasound imaging between different modes of delivery in prolonged second stage of labor with occipitoanterior fetal position.



Methods

We prospectively evaluated 41 women at term (≥ 37 weeks) with failure to progress in the second stage of labor. Only cases with occipitoanterior fetal position were included in the final analysis. These cases were classified into three groups: Cesarean section for failure to progress, vacuum extraction for failure to progress, and spontaneous delivery following prolonged second stage of labor. Transperineal ultrasound examination was performed just before digital examination and subsequent delivery. The angle between a line placed through the midline of the pubic symphysis and a line running from the inferior apex of the symphysis tangentially to the fetal skull (the so-called ‘angle of progression’) was measured offline by an observer blinded to the mode of delivery.



Results

There were 26 cases with occipitoanterior fetal position (Cesarean section, n = 5; vacuum extraction, n = 16; spontaneous delivery, n = 5). Logistic regression analysis showed a strong relationship between the angle of progression and the need for Cesarean delivery (R2 measure of fit = 55%, likelihood ratio chi-square P < 0.0001). When the angle of progression was 120°, the fitted probability of either an easy and successful vacuum extraction or spontaneous vaginal delivery was 90%.



Conclusions

This is the first report to document a strong relationship between an objective ultrasound marker (angle of progression) and the mode of delivery following prolonged second stage of labor with occipitoanterior fetal position. A predictive model using this parameter would allow better decision making regarding operative delivery for obstructed labor. Copyright © 2009 ISUOG. Published by John Wiley & Sons, Ltd.

Transperineal ultrasound imaging in prolonged second stage of labor with occipitoanterior presenting fetuses: how well does the 'angle of progression' predict the mode of delivery?

Objective
To investigate the ability of intrapartum translabial sonography to diagnose fetal station in the second stage of labor.

Methods
Patients with uncomplicated pregnancies at term gestation with fetuses in vertex presentation in the second stage of labor underwent serial translabial sonography and digital examinations. In a sagittal section of the maternal pelvis, the direction of the head was noted and categorized as downward, horizontal or upward. By rotating the transducer in the transverse plane the cerebral midline echo was also visualized and the rotation of the head was noted. Clinical and ultrasound data were compared using Somer's d-test.

Results
Sixty patients underwent a total of 168 clinical and sonographic examinations. When on the sonogram the fetal head was directed downward, the station assessed clinically was most frequently ≤ + 1 cm from the ischial spines (44/57 (77.2%) cases); when the direction was horizontal, the station was most frequently ≤ + 2 cm (53/59 (89.8%) cases); when the fetal head was directed upward, the station was usually ≥ + 3 cm (46/52 (88.5%) cases). Failure to visualize the cerebral midline or a rotation ≥ 45° were associated with a station of + 2 cm or less in 98/103 (95.1%) examinations. Conversely, a rotation of < 45° was associated with a station of + 3 cm or more in 45/65 (69.2%) examinations. All comparisons between clinical and sonographic findings demonstrated a statistically significant relationship (P < 0.0001). The probability of a station + 3 cm or more was particularly high when an upward direction of the head was seen in combination with a rotation of < 45° (40/42 (95.2%) examinations). The interobserver variability (Cohen's kappa 0.795 and 0.727 for station and rotation, respectively; P < 0.001) and intraobserver variability (0.845 for both station and rotation, P < 0.001) suggested good reproducibility of the method.

Conclusions
Translabial sonography allows a diagnosis of fetal station with an accuracy comparable to that of digital examination and may provide useful information for diagnosing obstructed labor in the second stage as well as assisting in the choice of instrumental delivery. Copyright © 2009 ISUOG. Published by John Wiley & Sons, Ltd.

Diagnosis of station and rotation of the fetal head in the second stage of labor with intrapartum translabial ultrasound

https://praenatal-zuerich.ch/wp-content/uploads/2014/05/Tutschek-et-al-ITU-parameters-BJOG-2010.pdf

A study of progress of labour using intrapartum translabial ultrasound, assessing head station, direction, and angle of descent.

Objective Having studied intrapartum translabial ultrasound (ITU) to define easily obtainable sonographic 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 head diameter and its movement with regard to the infrapubic line during pushing, and (iii) the ‘head 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 ‘head-up’ sign (head pointing ventrally) and objective descent of the fetal head 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 head direction were poor prognostic signs Conclusions ITU provides objective information on the dynamics of the second stage of labor, head station and head direction ITU may be used to assess the prognosis for operative vaginal delivery Copyright  2006 ISUOG Published by John Wiley & Sons, Ltd

https://obgyn.onlinelibrary.wiley.com/doi/pdf/10.1002/uog.3848

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

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