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.

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.

Objectives
To assess whether ultrasound experience or fetal head station affects the reliability of measurement of fetal head descent using the angle of progression on intrapartum ultrasound images obtained by a single experienced operator, and to determine reliability of measurements when images were acquired by different operators with variable ultrasound experience.

Methods
One experienced obstetrician performed 44 transperineal ultrasound examinations of women at term and in prolonged second stage of labor with the fetus in the occipitoanterior position. Three midwives without ultrasound experience, three obstetricians with 10 years' experience measured fetal head descent based on the angle of progression in the images obtained. The angle of progression was measured by two obstetricians in independent ultrasound examinations of 24 laboring women at term with the fetus in the cephalic position to allow assessment of the reliability of image acquisition. Intraclass correlation coefficients (ICCs) with 95% confidence interval (CI) were used to evaluate interobserver reliability and Bland–Altman analysis was used to assess interobserver agreement.

Results
In total, 444 measurements were performed and compared. Interobserver reliability with respect to offline image analysis was substantial (overall ICC, 0.72; 95% CI, 0.63–0.81). ICCs were 0.82 (95% CI, 0.70–0.89), 0.81 (95% CI, 0.71–0.88) and 0.61 (95% CI, 0.43–074) for observers with > 10 years', 10 years' and < 5 years' ultrasound experience (bias, −1.09°; 95% limits of agreement, −8.76 to 6.58). The reliability of measurement of the angle of progression following separate image acquisition by two experienced operators was similar to the reliability of offline image analysis (ICC, 0.86; 95% CI, 0.70–0.93).

Conclusions
Measurement of the angle of progression on transperineal ultrasound imaging is reliable regardless of fetal head station or the clinician's level of ultrasound experience. Copyright © 2010 ISUOG. Published by John Wiley & Sons, Ltd.

https://obgyn.onlinelibrary.wiley.com/doi/pdf/10.1002/uog.7521

Measurement of fetal head descent using the ‘angle of progression’ on transperineal ultrasound imaging is reliable regardless of fetal head station or ultrasound expertise

Objective

Several ultrasound parameters, including intrapartum transperineal ultrasound (ITU) head station, angle of progression (AOP), head–perineum distance (HPD) and head-symphysis distance (HSD), have been suggested to assess fetal head station during labor. The aim of this study was to analyze the relationship between these ultrasound parameters and to compare them with digital palpation.



Methods

We analyzed 106 stored volume dataset pairs that had been acquired at Stavanger University Hospital, Norway, from nulliparous women at term with prolonged first stage of labor. The volumes were acquired using a three-dimensional transducer applied between the labia majora in a mid-sagittal plane and perineally in a transverse plane. Digitally palpated head station and cervical dilatation were also noted. The results were compared using regression and correlation coefficients.



Results

There were good correlations between ITU head station and HPD (r = 0.71), between ITU head station and HSD (r = 0.74) and between HSD and HPD (r = 0.75). Palpated head station showed only moderate correlation with ITU head station (r = 0.52). Cervical dilatation showed a weak correlation with ITU head station (r = 0.30).



Conclusion

The ultrasound parameters showed a high degree of correlation with each other, but only moderate correlation to vaginally palpated fetal head station. Copyright © 2013 ISUOG. Published by John Wiley & Sons, Ltd.

Comparison between ultrasound parameters and clinical examination to assess fetal head station in labor

Objectives The aims of this study were, first, to establish the agreement between digital and ultrasound assessment of occipital position and, second, to evaluate the repeatability of the measurements of head direction, angle of the middle line, progression distance and angle of progression in women in the second stage of labor. Methods Digital examination and then transabdominal ultrasound examination was performed on 50 women in the second stage of labor to determine the fetal occipital position. We also obtained three-dimensional (3D) blocks of the fetal head by transperineal sonography, and two experts in 3D ultrasound measured head direction, angle of the middle line, progression distance and angle of progression. Intraclass correlation coefficients with 95% CIs, and Bland–Altman analysis, were used to evaluate intraobserver and interobserver repeatability of measurements. Results The fetal head position, determined by ultrasound examination, was occiput anterior in 33 (66%) cases and occiput lateral in 17 (34%) cases. Vaginal digital examination failed to identify the correct fetal head position by more than 45 ◦ in 33 (66%) cases. All four 3D ultrasound measurements were reproducible but the progression angle had the highest intraclass correlation coefficient for the same observer (0.94; 95% CI, 0.90–0.97) and for two different operators (0.84; 95% CI, 0.73–0.91). The progression angle was also the measurement for which smaller limits of agreement (LOA) were found in the Bland–Altman test, performed to calculate the intraobserver (bias 0.9; LOA, −9.2 to 11.1%) and interobserver (bias 1.5; LOA, −15.4 to 18.3%) variability. Conclusions Digital pelvic examination for determining the fetal head position during labor is not accurate. The most reproducible of the 3D measurements for progression of the fetal head in labor is the progression angle. Copyright  2010 ISUOG. Published by John Wiley & Sons, Ltd.

https://fetalmedicine.com/synced/fmf/2010_26.pdf

What is the most reliable ultrasound parameter for assessment of fetal head descent

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 determine whether cervical length measured by transvaginal ultrasound at 18–22 weeks could be used to predict the probability of Cesarean delivery in primiparous women at term. Methods: A total of 568 primiparous healthy patients with a singleton pregnancy had their cervical length measured using transvaginal ultrasound at the time of fetal anomaly survey at 18–22 weeks gestation. Patients with a cervical length shorter than 15 mm, those who delivered before term as well as patients with pre-existing medical diseases were excluded from the study group. The patients were followed prospectively and their term delivery data was collected including the gestational age at delivery, mode of delivery, reason for Cesarean section and neonatal outcome. Results: A total of 482 patients delivered at term and their delivery data were analysed. Patient data was categorized according to quartile of cervical length measured at 18–22 weeks. There was no difference in the baseline characteristics between the patients in the 4 quartiles (age, BMI, gestational age at delivery, neonatal weight). The Cesarean section rate was lowest in patients in the first quartile of cervical length (13.3%), and was significantly higher (p<0.001) in patient with a cervical length at the fourth quartile (40–50 mm). Failure of progress in labour as a cause for Cesarean section was significantly (p<0.001) more common in patients in the fourth quartile (40%). Conclusion: Cervical length measurement by transvaginal ultrasound at mid gestation can be used to predict the likelihood of Cesarean section at term in primiparous patients.

https://obgyn.onlinelibrary.wiley.com/doi/pdf/10.1002/uog.6503

OC08.09: Impact of transperineal ultrasound to assess fetal head descent on obstetrical interventions at full cervical dilatation

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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?

Measurement of fetal head descent using the ‘angle of progression’ on transperineal ultrasound imaging is reliable regardless of fetal head station or ultrasound expertise

OC08.09: Impact of transperineal ultrasound to assess fetal head descent on obstetrical interventions at full cervical dilatation