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?

Descent of the presenting part assessed with ultrasound

Fetal head descent can be expressed as fetal station and engagement. Station is traditionally based on clinical vaginal examination of the distal part of the fetal skull and related to the level of the ischial spines. Engagement is based on a transabdominal examination of the proximal part of the fetal head above the pelvic inlet. Clinical examinations are subjective, and objective measurements of descent are warranted. Ultrasound is a feasible diagnostic tool in labor, and fetal lie, station, position, presentation, and attitude can be examined. This review presents an overview of fetal descent examined with ultrasound. Ultrasound was first introduced for examining fetal descent in 1977. The distance from the sacral tip to the fetal skull was measured with A-mode ultrasound, but more convenient transperineal methods have since been published. Of those, progression distance, angle of progression, and head-symphysis distance are examined in the sagittal plane, using the inferior part of the symphysis pubis as reference point. Head-perineum distance is measured in the frontal plane (transverse transperineal scan) as the shortest distance from perineum to the fetal skull, representing the remaining part of the birth canal for the fetus to pass. At high stations, the fetal head is directed downward, followed with a horizontal and then an upward direction when the fetus descends in the birth canal and deflexes the head. Head descent may be assessed transabdominally with ultrasound and measured as the suprapubic descent angle. Many observational studies have shown that fetal descent assessed with ultrasound can predict labor outcome before induction of labor, as an admission test, and during the first and second stage of labor. Labor progress can also be examined longitudinally. The International Society of Ultrasound in Obstetrics and Gynecology recommends using ultrasound in women with prolonged or arrested first or second stage of labor, when malpositions or malpresentations are suspected, and before an operative vaginal delivery. One single ultrasound parameter cannot tell for sure whether an instrumental delivery is going to be successful. Information about station and position is a prerequisite, but head direction, presentation, and attitude also should be considered.

Soft-tissue dystocia due to paradoxical contraction of the levator ani as a cause of prolonged second stage: concept, diagnosis, and potential treatment

Smaller pelvic floor dimensions seem to have been an evolutionary need to provide adequate support for the pelvic organs and the fetal head. Pelvic floor dimension and shape contributed to the complexity of human birth. Maternal pushing associated with pelvic floor muscle relaxation is key to vaginal birth. Using transperineal ultrasound, pelvic floor dimensions can be objectively measured in both static and dynamic conditions, such as pelvic floor muscle contraction and pushing. Several studies have evaluated the role of the pelvic floor in labor outcomes. Smaller levator hiatal dimensions seem to be associated with a longer duration of the second stage of labor and a higher risk of cesarean and operative deliveries. Furthermore, smaller levator hiatal dimensions are associated with a higher fetal head station at term of pregnancy, as assessed by transperineal ultrasound. With maternal pushing, most women can relax their pelvic floor, thus increasing their pelvic floor dimensions. Some women contract rather than relax their pelvic floor muscles under pushing, which is associated with a reduction in the anteroposterior diameter of the levator hiatus. This phenomenon is called levator ani muscle coactivation. Coactivation in nulliparous women at term of pregnancy before the onset of labor is associated with a higher fetal head station at term of pregnancy and a longer duration of the second stage of labor. In addition, levator ani muscle coactivation in nulliparous women undergoing induction of labor is associated with a longer duration of the active second stage of labor. Whether we can improve maternal pelvic floor relaxation with consequent improvement in labor outcomes remains a matter of debate. Maternal education, physiotherapy, and visual feedback are promising interventions. In particular, ultrasound visual feedback before the onset of labor can help women increase their levator hiatal dimensions and correct levator ani muscle coactivation in some cases. Ultrasound visual feedback in the second stage of labor was found to help women push more efficiently, thus obtaining a lower fetal head station at ultrasound and a shorter duration of the second stage of labor. The available evidence on the role of any intervention aimed to aid women to better relax their pelvic floor remains limited, and more studies are needed before considering its routine clinical application.

Ultrasonographic Evaluation of the Second Stage of Labor according to the Mode of Delivery: A Prospective Study in Greece

BACKGROUND AND OBJECTIVES

Accurate diagnosis of labor progress is crucial for making well-informed decisions regarding timely and appropriate interventions to optimize outcomes for both the mother and the fetus. The aim of this study was to assess the progress of the second stage of labor using intrapartum ultrasound.

MATERIAL AND METHODS

This was a prospective study (December 2022-December 2023) conducted at the Third Department of Obstetrics and Gynecology, School of Medicine, Faculty of Health Sciences, Aristotle University of Thessaloniki, Greece. Maternal-fetal and labor characteristics were recorded, and two ultrasound parameters were measured: the angle of progression (AoP) and the head-perineum distance (HPD). The correlation between the two ultrasonographic values and the maternal-fetal characteristics was investigated. Multinomial regression analysis was also conducted to investigate any potential predictors of the mode of delivery.

RESULTS

A total of 82 women at the second stage of labor were clinically and sonographically assessed. The mean duration of the second stage of labor differed between vaginal and cesarean deliveries (65.3 vs. 160 min; p-value < 0.001) and between cesarean and operative vaginal deliveries (160 vs. 88.6 min; p-value = 0.015). The occiput anterior position was associated with an increased likelihood of vaginal delivery (OR: 24.167; 95% CI: 3.8-152.5; p-value < 0.001). No significant differences were identified in the AoP among the three different modes of delivery (vaginal: 145.7° vs. operative vaginal: 139.9° vs. cesarean: 132.1°; p-value = 0.289). The mean HPD differed significantly between vaginal and cesarean deliveries (28.6 vs. 41.4 mm; p-value < 0.001) and between cesarean and operative vaginal deliveries (41.4 vs. 26.9 mm; p-value = 0.002); it was correlated significantly with maternal BMI (r = 0.268; p-value = 0.024) and the duration of the second stage of labor (r = 0.256; p-value = 0.031). Low parity (OR: 12.024; 95% CI: 6.320-22.876; p-value < 0.001) and high HPD (OR: 1.23; 95% CI: 1.05-1.43; p-value = 0.007) were found to be significant predictors of cesarean delivery.

CONCLUSIONS

The use of intrapartum ultrasound as an adjunctive technique to the standard clinical evaluation may enhance the diagnostic approach to an abnormal labor progress and predict the need for operative vaginal or cesarean delivery.

Level of agreement between midwives and obstetricians performing ultrasound examination during labor

OBJECTIVE

To evaluate the level of agreement between ultrasound measurements to evaluate fetal head position and progress of labor by attending midwives and obstetricians after appropriate training.

METHODS

In this prospective study, women in the first stage of labor giving birth to a single baby in cephalic presentation at our Obstetric Unit between March 2018 and December 2019 were invited to participate; 109 women agreed. Transperineal and transabdominal ultrasound was independently performed by a trained midwife and an obstetrician. Two paired measurements were available for comparisons in 107 cases for the angle of progression (AoP), in 106 cases for the head-to-perineum distance (HPD), in 97 cases for the cervical dilatation (CD), and in 79 cases for the fetal head position.

RESULTS

We found a good correlation between the AoP measured by obstetricians and midwives (intra-class correlation coefficient [ICC] = 0.85; 95% confidence interval [CI] 0.80-0.89). There was a moderate correlation between the HPD (ICC = 0.75; 95% CI 0.68-0.82). There was a very good correlation between the CD measured (ICC = 0.94; 95% CI 0.91-0.96). There was a very good level of agreement in the classification of the fetal head position (Cohen's κ = 0.89; 95% CI 0.80-0.98).

CONCLUSIONS

Ultrasound assessment of fetal head position and progress of labor can effectively be performed by attending midwives without previous experience in ultrasound.

Intrapartum transperineal ultrasound: angle of progression to evaluate and predict the mode of delivery and labor progression

Intrapartum ultrasonography serves as a valuable tool for the objective evaluation of labor progression and effectively identifies underlying factors, such as asynclitism, in cases of abnormal labor progression. Among the various ultrasound measurement techniques, the angle of progression (AOP) demonstrates favorable reproducibility and accuracy in assessing fetal head descent. In the context of abnormal labor, interventions differ across different stages of labor, emphasizing the importance of investigating the utility of AOP according to labor stages in this review article. Pre-labor assessment of AOP can be beneficial in terms of counseling for the timing of induction of labor, while a wider AOP value during the prolonged first stage of labor has demonstrated a positive correlation with successful vaginal delivery and shorter time to delivery. In the second stage of labor, the AOP has exhibited efficacy in predicting the mode of delivery and complicated operative deliveries. Furthermore, it has assisted in predicting the duration of labor, thereby highlighting its potential as a decision-making model for labor progression. However, further research is needed to investigate aspects, such as the determination of cutoff values, of AOP, considering the multifaceted characteristics of labor progression, which are influenced by complex interactions among maternal, fetal, and other contributing factors.

Visual biofeedback for shortening second stage of labor: randomized controlled trial

OBJECTIVE

To determine whether visual biofeedback can be used during labor as an effective tool for shortening the second stage of labor and reducing the need for instrumental delivery.

METHODS

This was a single-center randomized controlled trial. Nulliparous women under epidural anesthesia were randomized at the point of full dilation into the biofeedback group (n = 50) or the control group (n = 50). Both groups received coached maternal pushing during four consecutive contractions, while an experienced obstetrician performed transperineal ultrasound. Only women in the biofeedback group observed the ultrasound display screen. Following this intervention, labor was managed routinely by the obstetric team. Angle of progression (AOP) was measured at rest and while pushing, before and during the first and fourth contractions. Second-stage duration and delivery outcomes were compared between groups.

RESULTS

Visual biofeedback did not affect the duration of the second stage, which lasted for a median of 2.28 (interquartile range (IQR), 1.25-3.10) h in the biofeedback group vs 2.08 (IQR, 1.58-3.02) h in the control group (P = 0.981). AOP was significantly higher in the biofeedback group compared with the control group, both at rest before the fourth contraction (mean ± SD, 142.6° ± 15.9° vs 136.8° ± 13.1°; P = 0.049) and while pushing during the fourth contraction (mean ± SD, 159.3° ± 19.2° vs 149.4° ± 15.1°; P = 0.005). The increase in AOP was significantly higher in the biofeedback compared with the control group between rest and pushing at the last push (mean ± SD, 16.6° ± 11.0° vs 12.6° ± 8.3°; P = 0.041) and between the first rest and last push (mean ± SD, 24.4° ± 13.6° vs 17.9° ± 11.3°; P = 0.011). The rate of intact perineum was similar between groups (12% vs 8%; P = 0.505).

CONCLUSIONS

Visual biofeedback during the second stage of labor may facilitate descent of fetal head during maternal pushing without affecting second-stage duration, possibly due to the short duration of the intervention. Future studies should focus on continuous intervention throughout the second stage of labor. © 2023 International Society of Ultrasound in Obstetrics and Gynecology.

Accurate evaluation of the progress of delivery with transperineal ultrasound may improve vaginal delivery: a single-center retrospective study

Although digital examination of the cervix is the standard method used worldwide for evaluating the progress of delivery, it is subjective. Transperineal ultrasound (TPU) is combined with digital evaluation for accurate assessment of fetal descent and rotation of the advanced part of the fetus. This retrospective study aimed to clarify the impact of introducing TPU on perinatal outcomes at Mie University Hospital. We analyzed singleton pregnant women who underwent delivery management at our hospital between April 2020 and March 2021. Perinatal outcomes were compared between patients who used TPU (TPU+ group) and those who did not (TPU- group). The angle of progression and head direction were measured. The rate of vaginal delivery was significantly increased (90.9% vs. 71.6%; P = 0.0017), and the second stage of labor was significantly prolonged in the TPU+ group (148.1 vs. 75.8 min; P < 0.0001). A significant difference was observed in termination in the latent phase between the TPU+ group [3/8 (37.5%) cases] and TPU- group [20/25 (80.0%) cases] (P = 0.036). The rate of vaginal delivery can be increased through accurate evaluation of the progress of delivery with TPU.

The sonopartogram

The assessment of labor progress from digital vaginal examination has remained largely unchanged for at least a century, despite the current major advances in maternal and perinatal care. Although inconsistently reproducible, the findings from digital vaginal examination are customarily plotted manually on a partogram, which is composed of a graphical representation of labor, together with maternal and fetal observations. The partogram has been developed to aid recognition of failure to labor progress and guide management-specific obstetrical intervention. In the last decade, the use of ultrasound in the delivery room has increased with the advent of more powerful, portable ultrasound machines that have become more readily available for use. Although ultrasound in intrapartum practice is predominantly used for acute management, an ultrasound-based partogram, a sonopartogram, might represent an objective tool for the graphical representation of labor. Demonstrating greater accuracy for fetal head position and more objectivity in the assessment of fetal head station, it could be considered complementary to traditional clinical assessment. The development of the sonopartogram concept would require further undertaking of serial measurements. Advocates of ultrasound will concede that its use has yet to demonstrate a difference in obstetrical and neonatal morbidity in the context of the management of labor and delivery. Taking a step beyond the descriptive graphical representation of labor progress is the question of whether a specific combination of clinical and demographic parameters might be used to inform knowledge of labor outcomes. Intrapartum cesarean deliveries and deliveries assisted by forceps and vacuum are all associated with a heightened risk of maternal and perinatal adverse outcomes. Although these outcomes cannot be precisely predicted, many known risk factors exist. Malposition and high station of the fetal head, short maternal stature, and other factors, such as caput succedaneum, are all implicated in operative delivery; however, the contribution of individual parameters based on clinical and ultrasound assessments has not been quantified. Individualized risk prediction models, including maternal characteristics and ultrasound findings, are increasingly used in women's health-for example, in preeclampsia or trisomy screening. Similarly, intrapartum cesarean delivery models have been developed with good prognostic ability in specifically selected populations. For intrapartum ultrasound to be of prognostic value, robust, externally validated prediction models for labor outcome would inform delivery management and allow shared decision-making with parents.

Intrapartum ultrasound use in clinical practice as a predictor of delivery mode during prolonged second stage of labor

PURPOSE

To determine the validity of intrapartum ultrasound (IPUS), and particularly the angle of progression (AOP), in predicting delivery mode when measured in real-life clinical practice among women with protracted second stages of labor.

METHODS

Using electronic medical records, nulliparous women with a second stage of labor of ≥ 3 h ("prolonged") and a documented AOP measurement during the second stage were identified. The ability of a single AOP measurement in "prolonged" second stage to predict a vaginal delivery (VD) was assessed. Fetal head descent, measured by AOP change/h (calculated from serial measurements), was compared between women who delivered vaginally and those who had a cesarean delivery (CD) for arrest of descent.

RESULTS

Of the 191 women who met the inclusion criteria, 62 (32.5%) delivered spontaneously, 96 (50.2%) had a vacuum extraction (VE) and 33 (17.3%) had a CD. The mean AOP was wider among women who had VD (spontaneous or VE) compared to those who had CD (153° ± 19 vs. 133° ± 17, p < 0.001). Wider AOPs were associated with higher rates of VD and an AOP ≥ 127° was associated with a VD rate of 88.6% (148/167). Among the 87 women who had more than one AOP measurement, the mean AOP change per hour was higher in the VD group than in the CD group (15.1° ± 11.4° vs. 6.2° ± 6.3°, p <  0.001).

CONCLUSION

Ultrasound-assessed fetal head station in nulliparous women with a protracted second stage of labor can be an accurate and objective additive tool in predicting the mode and interval time to delivery in real-life clinical practice.

Can Intrapartum Ultrasonography Improve the Placement of the Vacuum Cup in Operative Vaginal Deliveries?

Although the fetal head position has traditionally been evaluated by digital examination (DE), it has a failure rate ranging between 20 and 70%; hence, intrapartum transabdominal ultrasonography (TUS) has become relevant. We aimed to evaluate the utility of the TUS to identify the fetal head positions in vacuum-assisted deliveries. We performed a prospective observational study including 101 pregnant patients in active labor who required a vacuum-assisted delivery. The fetal head position was assessed by a DE and a TUS prior to vacuum cup placement. After delivery, the optimal vacuum cup placement was evaluated as the distance between the chignon and the flexion point ≤2 cm. The general concordance rate between the DE and TUS was 72.2%, with the poorest concordance rate for occiput posterior positions at 46.1%. In five cases (4.9%), it was not possible to determine the fetal head position through the DE. The correlation was higher in low and medium planes, with 77% and 68.1% concordance rates, respectively, while it was lower in high planes (60%). In 90.1% of cases, the vacuum cup placement was optimal. Our findings show that intrapartum transabdominal ultrasonography is a useful technique to identify the fetal head position allowing optimal placement of the vacuum cup necessary for correct vacuum-assisted delivery.

The head direction to the angle of progression ratio: a quantitative parameter for intrapartum evaluation of cephalic malposition

BACKGROUND

No previous study has evaluated the transitions of intrapartum transperineal ultrasound parameters during labor progression in cephalic malposition.

OBJECTIVE

We aimed to quantitate the characteristic trends of fetal head position and descent in cephalic malposition by analyzing the transitions of intrapartum transperineal ultrasound parameters and explore an indicator associated with the degree of cephalic malposition.

STUDY DESIGN

We retrospectively analyzed pregnant women who delivered at term from January 2018 to December 2020 at the University of Tokyo Hospital. The fetal occipital position was classified as occiput anterior and nonocciput anterior according to the fetal occipital angle of 0° to 75° and 75° to 180°, respectively. Fetal occipital angle was defined by the midline angle and position of the ocular orbit. The differences in the trends of head direction, head-symphysis distance, and progression distance relative to the angle of progression between occiput anterior and nonocciput anterior cases were evaluated. In addition, the parameters that showed differences were analyzed to evaluate their relationship to the degree of cephalic malposition.

RESULTS

A total of 502 images (occiput anterior, 319; nonocciput anterior, 183) met the inclusion criteria. The distribution of head direction values relative to the angle of progression was smaller in the nonocciput anterior group than in the occiput anterior group, whereas the head-symphysis distance and progression distance values relative to the angle of progression showed no difference in their distribution between the occiput anterior and nonocciput anterior groups. The ratio of head direction to the angle of progression was significantly smaller in the nonocciput anterior group than in the occiput anterior group (median [interquartile range], 0.03 [-0.02 to 0.10] vs 0.21 [0.12-0.28]; P<.0001). Furthermore, this ratio was negatively correlated with fetal occipital angle (Spearman correlation coefficient, -0.66).

CONCLUSION

Our results indicated that the head direction to angle of progression ratio reflects the deviation in the fetal head direction toward the maternal dorsal side, and decreases in proportion to the degree of cephalic malposition. This concept of deviation in the head direction as an indicator for evaluating cephalic malposition with intrapartum transperineal ultrasound may contribute to improving labor management in the case of cephalic malposition.

How to Reach the Best Ultrasound Performance in the Delivery Room

Ultrasonography is an instrument that is present in the maternal-fetal assessment throughout pregnancy and with widely documented benefits, but its use in intrapartum is becoming increasingly relevant. From the assessment of labor progression to the assessment of placental disorders, ultrasound can be used to correlate with physiological findings and physical examination, as its benefit in the delivery room cannot yet be proven. There are still few professionals with adequate training for its use in the delivery room and for the correct interpretation of data. Thus, this article aims to present a review of the entire applicability of ultrasound in the delivery room, considering the main stages of labor. There is still limited research in evidence-based medicine of its various possible uses in intrapartum, but it is expected that further studies can bring improvements in the quality of maternal and neonatal health during labor.

A framework for computing angle of progression from transperineal ultrasound images for evaluating fetal head descent using a novel double branch network

Background: Accurate assessment of fetal descent by monitoring the fetal head (FH) station remains a clinical challenge in guiding obstetric management. Angle of progression (AoP) has been suggested to be a reliable and reproducible parameter for the assessment of FH descent. Methods: A novel framework, including image segmentation, target fitting and AoP calculation, is proposed for evaluating fetal descent. For image segmentation, this study presents a novel double branch segmentation network (DBSN), which consists of two parts: an encoding part receives image input, and a decoding part composed of deformable convolutional blocks and ordinary convolutional blocks. The decoding part includes the lower and upper branches, and the feature map of the lower branch is used as the input of the upper branch to assist the upper branch in decoding after being constrained by the attention gate (AG). Given an original transperineal ultrasound (TPU) image, areas of the pubic symphysis (PS) and FH are firstly segmented using the proposed DBSN, the ellipse contours of segmented regions are secondly fitted with the least square method, and three endpoints are finally determined for calculating AoP. Results: Our private dataset with 313 transperineal ultrasound (TPU) images was used for model evaluation with 5-fold cross-validation. The proposed method achieves the highest Dice coefficient (93.4%), the smallest Average Surface Distance (6.268 pixels) and the lowest AoP difference (5.993°) by comparing four state-of-the-art methods. Similar results (Dice coefficient: 91.7%, Average Surface Distance: 7.729 pixels: AoP difference: 5.110°) were obtained on a public dataset with >3,700 TPU images for evaluating its generalization performance. Conclusion: The proposed framework may be used for the automatic measurement of AoP with high accuracy and generalization performance. However, its clinical availability needs to be further evaluated.

Prediction of labor outcome pilot study: evaluation of primiparous women at term

BACKGROUND

Emergency operative delivery is associated with high fetal and maternal morbidity and mortality. It is of high importance to find means to predict the delivery mode before the onset of labor.

OBJECTIVE

This study aimed to investigate the potential of combined sonographic and clinical determination to predict the mode of delivery at term.

STUDY DESIGN

An observational prospective cohort study was deployed in a tertiary maternity hospital (Emergency County Hospital Craiova). Unselected low-risk primiparous pregnant women were evaluated weekly at term for ultrasound determinations (estimated fetal weight, head descent parameters, occiput posterior, cervical length), Bishop score, and maternal characteristics (age, height, weight). A thorough statistical analysis determined which variables were significantly correlated with the delivery mode.

RESULTS

Data from 276 term primiparous women were analyzed. Head descent parameters were strongly and significantly correlated with each other, but only progression distance was correlated with the delivery mode (gestational weeks 37, 38, 41, and the week before delivery). In the week before delivery, measurements of head-to-perineum distance and angle of progression reached almost significant P levels of.055 and.07, respectively. The following variables were significantly correlated with the delivery mode: body mass index in all term evaluations; progression distance for weeks 37 and 38; maternal age for week 39; Bishop score, estimated fetal weight, and occiput posterior for week 40; and body mass index, estimated fetal weight, and progression distance for the week before delivery. We also provided logistic regression equations for each week with correct delivery mode prediction, except for week 38. Cutoff values were established for each significant parameter per week. The cutoff values must be read in conjunction with the area under the curve, which ranged from 0.55 to 0.73, depending on the variable.

CONCLUSION

There are strong and significant correlations among the "head descent" ultrasound measurements at term. Body mass index is predictive of labor outcomes throughout term evaluations. Progression distance and body mass index measured at 37 to 38 weeks' gestation correlate with the delivery mode and apparently can be used to forecast the delivery mode when the pregnancy reaches term. For the week before delivery, measurements of estimated fetal weight and progression distance can be used to forecast the delivery mode, perhaps as part of a policy for pregnant women with prelabor clinical signs. Larger studies with more data, particularly better-balanced data, are needed.

Angle of progression measured using transperineal ultrasound for prediction of uncomplicated operative vaginal delivery: systematic review and meta-analysis

OBJECTIVE

To determine whether intrapartum transperineal ultrasound measurement of the angle of progression (AoP) during the second stage of labor can predict uncomplicated operative vaginal delivery (OVD) using vacuum or forceps extraction.

METHODS

A systematic search in PubMed, EMBASE, Scopus, Web of Science and Google Scholar was performed from inception to February 2021. Studies assessing the predictive accuracy of AoP, measured using intrapartum transperineal ultrasound, for uncomplicated OVD, defined as successful vaginal delivery within three pulls using forceps or no more than two detachments of the vacuum extractor cup, were included. Study quality was assessed using the Quality Assessment of Diagnostic Accuracy Studies-2 (QUADAS-2) tool. Summary receiver-operating-characteristics (ROC) curves, pooled sensitivity and specificity, area under the ROC curve (AUC) and summary likelihood ratios (LRs) were calculated.

RESULTS

Seven studies reporting on a total of 782 patients undergoing OVD were included in this systematic review and meta-analysis. Second-stage AoP measured during maternal rest had a pooled sensitivity of 80% (95% CI, 59-92%) and specificity of 89% (95% CI, 76-95%), with a LR+ of 7.3 (95% CI, 3.1-15.8) for uncomplicated OVD. AoP measured during active pushing had a sensitivity of 91% (95% CI, 85-94%) and specificity of 83% (95% CI, 69-92%), with a LR+ of 5.4 (95% CI, 2.7-10.6) for uncomplicated OVD. The performance of AoP measured at rest was particularly high in nulliparous women, with a sensitivity of 87% (95% CI, 75-94%) and specificity of 90% (95% CI, 82-94%) for uncomplicated OVD.

CONCLUSION

AoP may be a reliable predictor for uncomplicated OVD when measured during the second stage of labor, especially in nulliparous women. © 2022 International Society of Ultrasound in Obstetrics and Gynecology.

Effects of Sex, Age and Height on Symphysis–Ischial Spine Distance Measured on a Pelvic CT

Objective: To examine the influence of age, sex and height on the symphysis–ischial spine distance (SID) measured on pelvic Computed tomography (CT)images in subjects of reproductive age, and to determine the interobserver reproducibility. This measurement (SID) is of great importance because the use of intrapartum ultrasound is based on the assumption of a specific value (30 mm) of such a measurement. Methods: This was a cross-sectional descriptive study in which SID was measured in subjects aged 20 to 44 years who had been scheduled for pelvic CT at our centre from January 2018 to May 2021 for different reasons. Radiographic measurements of the pelvis were obtained through the multiplanar reconstruction of the CT image. The images obtained from all of the participants were independently assessed by three senior radiologists, and the SID measurements made by each one were blinded from those of the remaining observers. Correlations between the SID and patient age, height and sex were analyzed by univariate and multivariate linear regression. Results: The mean SID for 87 of the enrolled participants (45 women, 42 men) was 28.2 ± 6.25 mm. Among the observers, the mean difference in this distance was 1 to 2 mm, and was scarcely related to measurement size, with agreement being greater than 70%. The mean SID was significantly related to sex and height (SID = −24.9 − 6.51 × sex (0 or 1) + 0.34 × height (cm); p = 0.01; sex equals 1 for a man and 0 for a woman), such that it was a mean of 2.5 mm greater in women than men (29.50 mm vs. 26.99 mm). Conclusion: Measurements of SID on CT images show good interobserver reproducibility, and are related to sex and height.

Uncertain fetal head engagement: a prospective randomized controlled trial comparing digital exam with angle of progression

BACKGROUND

Uncertain fetal head engagement represents 4% of obstetrical situations associated with an increased risk of postpartum hemorrhage, notably in cases of cesarean delivery and increased neonatal impairment owing to failed vaginal instrumental delivery. In this obstetrical condition, cesarean delivery is recommended, but vaginal delivery is possible in two-thirds of the cases. During the second stage of labor, the descent of the fetal head can be assessed by sonography, particularly by measuring the angle of progression.

OBJECTIVE

To evaluate, after a prolonged second stage of labor, the impact of measuring the angle of progression in addition to a digital examination on cesarean delivery rates when fetal head engagement remains uncertain.

STUDY DESIGN

This open multicenter randomized pragmatic trial included women at term with a singleton cephalic fetus in a clinical occiput anterior position after a prolonged 2-hour second stage of labor with uncertain fetal head engagement. After inclusion in the study, an independent investigator performed ultrasound systematically to confirm the occiput anterior position and measured the angle of progression at the climax of Valsalva pushing. This operator did not participate in labor management. In the study group but not in the control group, the angle of progression was communicated to the obstetrician in charge of labor management. Obstetricians were encouraged to attempt vaginal birth if the angle of progression was >120°. The primary outcome was the cesarean delivery rate. Secondary outcomes were operative delivery rate (cesarean delivery and operative vaginal delivery), maternal complications (third and fourth-degree perineal tears, failed vaginal instrumental delivery, postpartum hemorrhage, hysterectomy), and neonatal outcomes (Apgar score <5 at 10 minutes, umbilical arterial pH <7.10, neonatal wounds, neonatal intensive care unit admission).

RESULTS

A total of 45 women were included in the study. Occiput anterior position was confirmed in 33 women: 16 in the study group and 17 in the control group. Women's characteristics at baseline were similar between the groups. The median (range) angles of progression were similar: 138.4° (15) and 140.3° (16.9) in the study and control group, respectively. Cesarean delivery rates were 12.5% in the study group and 41.1% in the control group (P=.06). Secondary outcomes were similar between the 2 groups. No failed vaginal instrumental delivery was reported.

CONCLUSION

Measurement of the angle of progression in addition to digital examination when fetal head engagement remained uncertain showed promising results in decreasing cesarean delivery rates. A larger multicenter randomized controlled trial is needed to confirm these results.

The correlation between levator ani co-activation and fetal head regression on maternal pushing at term

OBJECTIVE

To assess the correlation between fetal head regression and levator ani muscle (LAM) co-activation under Valsalva maneuver.

STUDY DESIGN

This study was a secondary analysis of a prospective cohort study on the association between the angle of progression (AoP) and labor outcome. We scanned a group of nulliparous women at term before the onset of labor at rest and under maximum Valsalva maneuver. In addition to the previously calculated AoP, in the present study, we measured the anteroposterior diameter of LAM hiatus (APD) on each ultrasound image. LAM co-activation was defined as APD at Valsalva less than that at rest, whereas fetal head regression was defined as AoP at Valsalva less than that at rest. We calculated the correlation between the two phenomena. Finally, we examined various labor outcomes according to the presence, absence, or co-existence of these two phenomena.

RESULTS

We included 469 women. A total of 129 (27.5%) women presented LAM co-activation while 50 (10.7%) showed head regression. Only 15 (3.2%) women showed simultaneous head regression and LAM co-activation. Women with coexisting LAM co-activation and head regression had the narrowest AoP at Valsalva in comparison with other study groups (p < .001). In addition, they had the highest risk of Cesarean delivery (40%) and longest first, second, and active second stage durations, although none of these reached statistical significance.

CONCLUSION

In nulliparous women at term before the onset of labor fetal head regression and LAM co-activation at Valsalva are two distinct phenomena that uncommonly coexist.

Intrapartum ultrasound measurement of angle of progression at the onset of the second stage of labor for prediction of spontaneous vaginal delivery in term singleton pregnancies: a systematic review and meta-analysis

OBJECTIVE

This study aimed to investigate the diagnostic performance of transperineal ultrasound-measured angles of progression at the onset of the second stage of labor for the prediction of spontaneous vaginal delivery in singleton term pregnancies with cephalic presentation.

DATA SOURCES

We performed a predefined systematic search in PubMed, Embase, Scopus, Web of Science, and Google Scholar from inception to February 5, 2021.

STUDY ELIGIBILITY CRITERIA

Prospective cohort studies that evaluated the diagnostic performance of transperineal ultrasound-measured angles of progression (index test) at the onset of the second stage of labor (ie, when complete cervical dilation is diagnosed) for the prediction of spontaneous vaginal delivery (reference standard) were eligible for inclusion. Eligible studies were limited to those published as full-text articles in the English language and those that included only parturients with a singleton healthy fetus at term with cephalic presentation.

STUDY APPRAISAL AND SYNTHESIS METHODS

Study quality was assessed using the Quality Assessment of Diagnostic Accuracy Studies 2 tool. Summary receiver operating characteristic curves, pooled sensitivities and specificities, area under the curve, and summary likelihood ratios were calculated using the Stata software. Subgroup analyses were done based on angle of progression ranges of 108° to 119°, 120° to 140°, and 141° to 153°.

RESULTS

A total of 8 studies reporting on 887 pregnancies were included. Summary estimates of the sensitivity and specificity of transperineal ultrasound-measured angle of progression at the onset of the second stage of labor for predicting spontaneous vaginal delivery were 94% (95% confidence interval, 88%-97%) and 47% (95% confidence interval, 18%-78%), respectively, for an angle of progression of 108° to 119°, 81% (95% confidence interval, 70%-89%) and 73% (95% confidence interval, 57%-85%), respectively, for an angle of progression of 120° to 140°, and 66% (95% confidence interval, 56%-74%) and 82% (95% confidence interval, 66%-92%), respectively, for an angle of progression of 141° to 153°. Likelihood ratio syntheses gave overall positive likelihood ratios of 1.8 (95% confidence interval, 1-3.3), 3 (95% confidence interval, 2-4.7), and 3.7 (95% confidence interval, 1.7-8.1) and negative likelihood ratios of 0.13 (95% confidence interval, 0.07-0.22), 0.26 (95% confidence interval, 0.18-0.38), and 0.42 (95% confidence interval, 0.29-0.60) for angle of progression ranges of 108° to 119°, 120° to 140°, and 141° to 153°, respectively.

CONCLUSION

Angle of progression measured by transperineal ultrasound at the onset of the second stage of labor may predict spontaneous vaginal delivery in singleton, term, cephalic presenting pregnancies and has the potential to be used along with physical examinations and other clinical factors in the management of labor and delivery.

Fetal head descent assessed by transabdominal ultrasound: a prospective observational study

BACKGROUND

Determining fetal head descent, expressed as fetal head station and engagement is an essential part of monitoring progression in labor. Assessing fetal head station is based on the distal part of the fetal skull, whereas assessing engagement is based on the proximal part. Prerequisites for assisted vaginal birth are that the fetal head should be engaged and its lowermost part at or below the level of the ischial spines. The part of the fetal head above the pelvic inlet reflects the true descent of the largest diameter of the skull. In molded (reshaped) fetal heads, the leading bony part of the skull may be below the ischial spines while the largest diameter of the fetal skull still remains above the pelvic inlet. An attempt at assisted vaginal birth in such a situation would be associated with risks. Therefore, the vaginal or transperineal assessments of station should be supplemented with a transabdominal examination. We suggest a method for the assessment of fetal head descent with transabdominal ultrasound.

OBJECTIVE

To investigate the correlation between transabdominal and transperineal assessment of fetal head descent, and to study fetal head shape at different labor stages and head positions.

STUDY DESIGN

Women with term singleton cephalic pregnancies admitted to the labor ward for induction of labor or in spontaneous labor, at the Cairo University Hospital and Oslo University Hospital from December 2019 to December 2020 were included. Fetal head descent was assessed with transabdominal ultrasound as the suprapubic descent angle between a longitudinal line through the symphysis pubis and a line from the upper part of the symphysis pubis extending tangentially to the fetal skull. We compared measurements with transperineally assessed angle of progression and investigated interobserver agreement. We also measured the part of fetal head above and below the symphysis pubis at different labor stages.

RESULTS

The study population comprised 123 women, of whom 19 (15%) were examined before induction of labor, 8 (7%) in the latent phase, 52 (42%) in the active first stage and 44 (36%) in the second stage. The suprapubic descent angle and the angle of progression could be measured in all cases. The correlation between the transabdominal and transperineal measurements was -0.90 (95% confidence interval, -0.86 to -0.93). Interobserver agreement was examined in 30 women and the intraclass correlation coefficient was 0.98 (95% confidence interval, 0.95-0.99). The limits of agreement were from -9.5 to 7.8 degrees. The fetal head was more elongated in occiput posterior position than in non-occiput posterior positions in the second stage of labor.

CONCLUSION

We present a novel method of examining fetal head descent by assessing the proximal part of the fetal skull with transabdominal ultrasound. The correlation with transperineal ultrasound measurements was strong, especially early in labor. The fetal head was elongated in the occiput posterior position during the second stage of labor.

Association between ultrasound measured angle of progression and remaining time in labor: a systematic review

OBJECTIVES

To evaluate the association between ultrasound measured angle of progression (AoP) during labor and time to delivery (TTD) or second stage of labor duration (SSLD).

METHODS

This systematic review (SR) was reported according to PRISMA statement 2020. Databases investigated were MEDLINE, CINHAL, Embase, Scopus, Web of Science. Other sources were references or related articles of included studies, Google Scholar, clinicaltrials.gov, thesis, expert groups. Main keywords: angle of progression, transperineal ultrasound, delivery, labor. Inclusion criteria were observational studies, single term pregnancy, cephalic presentation, AoP measurement during the first stage of labor or at the beginning of the second stage, without date restrictions. Language included: English, Italian, French, Spanish. Studies selection, evaluation of the risk of bias with Quality in Prognosis Studies (QUIPS) tool, and data extraction were carried out by two authors blindly and independently, with disagreement resolution by a third author. Qualitative summary of the results. This SR was registered on PROSPERO, number CDR42021232015.

RESULTS

Of 428 records, 14 were included, published from 2009 to 2021, cumulatively analyzing 2498 women. All studies highlighted an inverse relationship between AoP and TTD. Some have identified an AoP cutoff, contained in a range between 110° and 129°, beyond which the duration of labor is significantly shorter. Others, a range between 137° and 160°, beyond which the duration of the expulsive period is significantly shorter. Finally, some factors influence this association: parity, epidural, and oxytocin.

CONCLUSIONS

This SR confirms a significant association between AoP in labor and TTD. In clinical practice, AoP could help to predict the duration of labor, facilitating decision-making. The main limitations of this SR were the low number of included studies, their heterogeneity, and the high risk of bias related to confounding factors. For future research, further studies are needed to increase the strength of the evidence, obtain stratified results according to patients' characteristics and investigate groups of patients who have not yet been evaluated.

Association between level of training and reliability of intrapartum transperineal ultrasound measurement of angle of progression

OBJECTIVES

Intrapartum transperineal ultrasound (ITU) is an accepted tool for assessing fetal head position and station prior to operative vaginal delivery attempt. However, the validity of intrapartum ultrasound in real-life obstetrics with operators at different proficiency level is yet to be established. We aimed to investigate the association between operator level of training and reliability of angle of progression (AOP) measurements in real-life obstetrics.

METHODS

This was a retrospective study in one university medical center. We included women who underwent ITU for the measurement of AOP, before vacuum assisted delivery from November 2017 to September 2020. AOP measurements performed by residents and their correlation to head station were compared to those performed by specialists.

RESULTS

A total of 320 cases met the inclusion criteria. In 234 of them, AOP measurements were performed by specialists and in 86 by residents. Average AOP for each station was similar between the specialists and the residents groups, indicating similar accuracy. However, measurements in the residents group were more scattered (median deviation 11.4° vs. 8.9°, respectively, p = .021), indicating poorer precision.

CONCLUSIONS

AOP measurements performed by obstetrics and gynecology (OBGYN) specialists are more precise than those performed by residents. Efforts should be taken to improve ITU training and to implement assessment of performance programs.

The use of ultrasound, fibronectin and other parameters to predict the success of labour induction

Induction of labour is a common obstetrical procedure and is undertaken when the benefits of delivery are considered to outweigh the risks of continuation of pregnancy. However, more than one-fifth of induction cases fail to result in vaginal births and lead to unplanned caesarean deliveries, which compromise the birth experience and have negative clinical and resource implications. The need for accurate prediction of successful labour induction is increasingly recognised and many researchers have attempted to evaluate the potential predictability of different factors including maternal characteristics, Bishop score, various biochemical markers and ultrasound markers and derive predictive models to address this issue.

Breech progression angle: new feasible and reliable transperineal ultrasound parameter for assessment of fetal breech descent in birth canal

OBJECTIVE

To assess the feasibility and reliability of transperineal ultrasound in the assessment of fetal breech descent in the birth canal, by measuring the breech progression angle (BPA).

METHODS

Women with a singleton pregnancy with the fetus in breech presentation between 34 and 41 weeks' gestation were recruited. Transperineal ultrasound images were acquired in the midsagittal view for each woman, twice by one operator and once by another. Each operator measured the BPA after anonymization of the transperineal ultrasound images. BPA was defined as the angle between a line running along the long axis of the pubic symphysis and another line extending from the most inferior portion of the pubic symphysis tangentially to the lowest recognizable fetal part in the maternal pelvis. Each operator was blinded to all other measurements performed for each woman. Intra- and interobserver reproducibility of BPA measurement was evaluated using the intraclass correlation coefficient (ICC). To investigate the presence of any bias, intra- and interobserver agreement was also analyzed using Bland-Altman analysis. Student's t-test and Levene's W₀ test were used to investigate whether a number of different clinical factors had an effect on systematic differences and homogeneity, respectively, between BPA measurements.

RESULTS

Overall, 44 women were included in the analysis. BPA was measured successfully by both operators on all images. Both intra- and interobserver agreement analyses showed excellent reproducibility in BPA measurement, with ICCs of 0.88 (95% CI, 0.80-0.93) and 0.83 (95% CI, 0.71-0.90), respectively. The mean difference between measurements was 0.4° (95% CI, -1.4 to 2.2°) for intraobserver repeatability and -0.4° (95% CI, -2.6 to 1.8°) for interobserver repeatability. The upper limits of agreement were 12.0° (95% CI, 8.9-15.1°) and 13.6° (95% CI, 9.9-17.3°) for intra- and interobserver repeatability, respectively. The lower limits of agreement were -11.2° (95% CI, -14.3 to -8.1°) and -14.4° (95% CI, -18.2 to -10.7°) for intra- and interobserver repeatability, respectively. No systematic difference between BPA measurements was found on either intra- or interobserver agreement analysis. None of the clinical factors examined (maternal body mass index, maternal age, gestational age at the ultrasound scan and parity) showed a statistically significant effect on intra- or interobserver reliability.

CONCLUSIONS

BPA represents a new feasible and highly reproducible measurement for the evaluation of fetal breech descent in the birth canal. Future studies assessing its usefulness in the prediction of successful external cephalic version and breech vaginal delivery are needed. © 2021 International Society of Ultrasound in Obstetrics and Gynecology.

Sonographic Evaluation of the Mechanism of Active Labor (SonoLabor Study): observational study protocol regarding the implementation of the sonopartogram

INTRODUCTION

Over the last decades, a large body of literature has shown that intrapartum clinical digital pelvic estimations of fetal head position, station and progression in the pelvic canal are less accurate, compared with ultrasound (US) scan. Given the increasing evidence regarding the advantages of using US to evaluate the mechanism of labour, our study protocol aims to develop sonopartograms for fetal cephalic presentations. They will allow for a more objective evaluation of labour progression than the traditional labour monitoring, which could enable more rapid decisions regarding the mode of delivery.

METHODS/ANALYSIS

This is a prospective observational study performed in three university hospitals, with an unselected population of women admitted in labour at term. Both clinical and US evaluations will be performed assessing fetal head position, descent and rotation. Specific US parameters regarding fetal head position, progression and rotation will be recorded to develop nomograms in a similar way that partograms were developed. The primary outcome is to develop nomograms for the longitudinal US assessment of labour in unselected nulliparous and multiparous women with fetal cephalic presentation. The secondary aims are to assess the sonopartogram differences in occiput anterior and posterior deliveries, to compare the labour trend from our research with the classic and other recent partogram models and to investigate the capability of the US labour monitoring to predict the outcome of spontaneous vaginal delivery.

ETHICS AND DISSEMINATION

All protocols and the informed consent form comply with the Ministry of Health and the professional society ethics guidelines. University ethics committees approved the study protocol. The trial results will be published in peer-reviewed journals and at the conference presentations. The study will be implemented and reported in line with the Strengthening the Reporting of Observational Studies in Epidemiology statement.

TRIAL REGISTRATION NUMBER

ClinicalTrials.gov Registry (NCT02326077).

The maternal pelvic floor and labor outcome

Vaginal birth is the major cause of pelvic floor damage. The development of transperineal ultrasound has improved our understanding of the relationship between vaginal birth and pelvic floor dysfunction. The female pelvic floor dimensions and function can be assessed reliably in pregnant women. Maternal pushing associated with pelvic floor muscle relaxation is the central requirement of vaginal birth. Many studies have evaluated the role of the pelvic floor on labor outcomes. Smaller levator hiatal dimensions and incomplete or absent levator ani muscle relaxation seem to be associated with a longer duration of the second stage of labor and a higher risk of cesarean and operative deliveries. Here, we presented an overview of the current knowledge of the correlation between female pelvic floor dimension and function, as assessed by transperineal ultrasound, and labor outcome.

A Novel Partogram for Stages 1 and 2 of Labor Based on Fetal Head Station Measured by Ultrasound: A Prospective Multicenter Cohort Study

OBJECTIVE

This study was aimed to describe continuous labor curves, including second stage, based on fetal head station.

STUDY DESIGN

We performed a prospective multicenter cohort study. The inclusion criteria were women with singleton uncomplicated cephalic term pregnancies in labor, who delivered vaginally. We used a device that combines ultrasound imaging with position-tracking technology to monitor the head station noninvasively throughout labor. We collected data on demographics, labor parameters, and delivery and neonatal outcomes.

RESULTS

A total of 613 women delivered vaginally, 327 (53.3%) were nulliparous, while 286 (46.7%) were multiparous. Time to delivery (TTD) diminished progressively with descent of the fetal head. When the head is engaged, the labor curve of multiparous women demonstrated a more prominent downward shift in curve as compared with nulliparous women. When comparing multipara and nullipara at engagement level, the median TTD was 1 and 1.62 hours, respectively. In 95% of women with unengaged head during the second stage, TTD of nulliparous and multiparous women were less than 3.8 and 3 hours, respectively.

CONCLUSION

While current labor curves end at full dilatation, the described curves were developed throughout stages 1 and 2 of labor. The TTD, according to the station curves, shows an acceleration of labor, once passed the engagement level, especially in multiparous women.

Fetal head progression and regression on maternal pushing at term and labor outcome

OBJECTIVES

The aim of our study was two-fold. First, to evaluate the association between the change in the angle of progression (AoP) on maternal pushing and labor outcome. Second, to assess the incidence and clinical significance of the reduction of AoP on maternal pushing.

METHODS

This was a prospective cohort study of nulliparous women with singleton pregnancy at term. AoP was measured at rest and on maximum Valsalva maneuver before the onset of labor, and the difference between AoP on maximum Valsalva and that at rest (ΔAoP) was calculated for each woman. Following delivery and data collection, we assessed the association between ΔAoP and various labor outcomes, including Cesarean section (CS), duration of the first, second and active second stages of labor, Apgar score and admission to the neonatal intensive care unit (NICU). The prevalence of women with reduction of AoP on maximum Valsalva maneuver (AoP-regression group) was calculated and its association with the mode of delivery and duration of different stages of labor was assessed.

RESULTS

Overall, 469 women were included in the analysis. Among these, 273 (58.2%) had spontaneous vaginal birth, 65 (13.9%) had instrumental delivery and 131 (27.9%) underwent CS. Women in the CS group were older, had narrower AoP at rest and on maximum Valsalva, higher rate of epidural administration and lower 1-min and 5-min Apgar scores in comparison with the vaginal-delivery group. ΔAoP was comparable between the two groups. On Pearson's correlation analysis, AoP at rest and on maximum Valsalva maneuver had a significant negative correlation with the duration of the first stage of labor. ΔAoP showed a significant negative correlation with the duration of the active second stage of labor (Pearson's r, -0.125; P = 0.02). Cox regression model analysis showed that ΔAoP was associated independently with the duration of the active second stage (hazard ratio, 1.014 (95% CI, 1.003-1.025); P = 0.012) after adjusting for maternal age and body mass index. AoP reduction on maximum Valsalva was found in 73 (15.6%) women. In comparison with women who showed no change or an increase in AoP on maximum Valsalva, the AoP-regression group did not demonstrate significant difference in maternal characteristics, mode of delivery, rate of epidural analgesia, duration of the different stages of labor or rate of NICU admission.

CONCLUSIONS

In nulliparous women at term before the onset of labor, narrower AoP at rest and on maximum Valsalva, reflecting fetal head engagement, is associated with a higher risk of Cesarean delivery. The increase in AoP from rest to Valsalva, reflecting more efficient maternal pushing, is associated with a shorter active second stage of labor. Fetal head regression on maternal pushing is present in about 16% of women and does not appear to have clinical significance. © 2020 International Society of Ultrasound in Obstetrics and Gynecology.

The role of the angle of progression in the prediction of the outcome of occiput posterior position in the second stage of labor

BACKGROUND

Occiput posterior position is the most frequent cephalic malposition, and its persistence at delivery is associated with a higher risk of maternal and perinatal morbidity. Diagnosis and management of occiput posterior position remain a clinical challenge. This is partly caused by our inability to predict fetuses who will spontaneously rotate into occiput anterior from those who will have persistent occiput posterior position. The angle of progression, measured with transperineal ultrasound, represents a reliable tool for the evaluation of fetal head station during labor. The relationship between the persistence of occiput posterior position and fetal head station in the second stage of labor has not been previously assessed.

OBJECTIVE

This study aimed to evaluate the role of fetal head station, as measured by the angle of progression, in the prediction of persistent occiput posterior position and the mode of delivery in the second stage of labor.

STUDY DESIGN

We recruited a nonconsecutive series of women with posterior occiput position diagnosed by transabdominal ultrasound in the second stage of labor. For each woman, a transperineal ultrasound was performed to measure the angle of progression at rest. We compared the angle of progression between women who delivered fetuses in occiput anterior position and those with persistent occiput posterior position at delivery. Receiver operating characteristics curves were performed to evaluate the accuracy of the angle of progression in the prediction of persistent occiput posterior position. Finally, we performed a multivariate logistic regression to determine independent predictors of persistent occiput posterior position.

RESULTS

Overall, 63 women were included in the analysis. Among these, 39 women (62%) delivered in occiput anterior position, whereas 24 (38%) delivered in occiput posterior position (persistent occiput posterior position). The angle of progression was significantly narrower in the persistent occiput posterior position group than in women who delivered fetuses in occiput anterior position (118.3°±12.2° vs 127.5°±10.5°; P=.003). The area under the receiver operating characteristics curve was 0.731 (95% confidence interval, 0.594-0.869) with an estimated best cutoff range of 121.5° (sensitivity of 72% and specificity of 67%). On logistic regression analysis, the angle of progression was found to be independently associated with persistence of occiput posterior position (odds ratio, 0.942; 95% confidence interval, 0.889-0.998; P=.04). Finally, women who underwent cesarean delivery had significantly narrower angle of progression than women who had a vaginal delivery (113.5°±8.1 vs 128.0°±10.7; P<.001). The area under the receiver operating characteristics curve for the prediction of cesarean delivery was 0.866 (95% confidence interval, 0.761-0.972). At multivariable logistic regression analysis including the angle of progression, parity, and gestational age at delivery, the angle of progression was found to be the only independent predictor associated with cesarean delivery (odds ratio, 0.849; 95% confidence interval, 0.775-0.0930; P<.001).

CONCLUSION

In fetuses with occiput posterior at the beginning of the second stage of labor, narrower values of the angle of progression are associated with higher rates of persistent occiput posterior position at delivery and a higher risk of cesarean delivery.

Intrapartum ultrasound and the choice between assisted vaginal and cesarean delivery

Inaccurate assessment of the fetal head position and station might increase the risk for difficult or failed assisted vaginal delivery. Compared with digital vaginal examination, an ultrasound examination is objective and more accurate. The International Society of Ultrasound in Obstetrics and Gynecology has issued practical guidelines on intrapartum ultrasound in 2018 and recommended that an ultrasound assessment should be conducted when there is suspected delay or arrest of the first or second stage of labor or before considering assisted vaginal delivery. Fetal head position is assessed transabdominally by identifying the fetal occiput, orbit, or midline cerebral echo. Studies have shown that ultrasound assessment improved the correct diagnosis of fetal head position and accuracy of instrument placement, however, it did not reduce morbidity. Studies on ultrasound assessment of asynclitism are limited but show promising results. Fetal head station is assessed transperineally in the midsagittal or axial plane. Of the various ultrasound parameters, angle of progression and head-perineum distance are the most widely studied and found to be highly correlated with the clinical fetal head station. An angle of progression of 120° correlates with a clinical head station of 0 and is an important landmark for engagement of successful vaginal delivery, whereas an angle of progression of 145° correlates with a clinical head station of ≥+2 and has been associated with successful assisted vaginal delivery. In contrast, a head perineum distance of ≥40 mm has been associated with an increased risk for difficult assisted vaginal delivery. A "head-up" direction of descent assessed transperineally in sagittal plane is also a favorable factor for successful vaginal delivery. Current evidence seems to suggest that a prediction model with >1 sonographic parameter performed better than a model that only used 1 parameter. We suggest that an algorithm model incorporating both clinical and sonographic parameters would be useful in guiding clinicians on their decision for assisted vaginal delivery.

Advanced midwifery practice: intrapartum ultrasonography to assess fetal head station and comparison with vaginal digital examination

BACKGROUND

Vaginal digital examination is considered the gold standard to evaluate patients during labor and delivery. However, transperineal ultrasound has been suggested as an effective tool in determining fetal head station during labor. Angle of progression (AOP), head-perineal distance (HPD) and head-symphysis distance (HSD) are reliable parameters to assess fetal head station during labor. The study aims were to evaluate how midwives can use AOP, HSD, HPD to assess the accuracy of digital vaginal exploration limited to the fetal head station.

METHODS

Trained midwives for ultrasound analyses performed transperineal ultrasounds during the first stage of labor with 2D-convex probe in 62 pregnant women at term with a single fetus in cephalic presentation. Immediately before the intrapartum ultrasound, the birth attendant performed a digital examination to assess cervical dilatation and head station. The ultrasound scans were compared to the digital vaginal examination through the Tutschek's formula.

RESULTS

AOP was wider in women who delivered vaginally without any complication if compared to "complicated delivery" group. HPD and HSD were greater in women who underwent an operative vaginal delivery or caesarean section. The vaginal exploration accuracy was 34%, but when ±1 cm was considered as tolerated, the overall accuracy was 74.19%.

CONCLUSIONS

Midwives may include ultrasounds in their clinical practice after adequate training or under the supervision of an ultrasound professional as an adjunct tool during labor to evaluate its progress and prevent any deviation from physiology.

Transabdominal and transperineal ultrasound vs routine care before instrumental vaginal delivery - A randomized controlled trial

INTRODUCTION

The role of intrapartum ultrasound as an ancillary method to instrumental vaginal delivery is yet to be determined. This study aimed to compare the use of transabdominal and transperineal ultrasound with routine clinical care before performing an instrumental vaginal delivery, regarding the incidence of adverse maternal and neonatal outcomes.

MATERIAL AND METHODS

A randomized controlled trial was conducted between October 2016 and March 2019 in two tertiary care maternity hospitals in Lisbon, Portugal. Women at term, with full cervical dilatation, singleton fetuses in cephalic presentation, and with an established indication for instrumental vaginal delivery, were approached for enrollment. After informed consent was obtained, randomization into one of two groups was carried out. In the experimental arm, women underwent transabdominal ultrasound for determination of the fetal head position and transperineal ultrasound for evaluation of the angle of progression, before instrumental vaginal delivery. In the control arm, no ultrasound was carried out before instrumental vaginal delivery. Primary outcomes were composite measures of maternal and neonatal morbidity. Composite maternal morbidity consisted of severe postpartum hemorrhage, perineal trauma, and prolonged hospital stay. Composite neonatal morbidity consisted of low 5-minute Apgar score, umbilical artery metabolic acidosis, birth trauma, and neonatal intensive care unit admission.

RESULTS

A total of 222 women were enrolled (113 in the experimental arm and 109 in the control arm). No significant differences between the two arms were found in composite measures of maternal (23.9% in the experimental group vs 22.9% in the control group, odds ratio 1.055, 95% CI 0.567-1.964) or neonatal morbidity (9.7% in the experimental group vs 6.4% in the control group, odds ratio 1.571, 95% CI 0.586-4.215), nor in any of the individual outcomes.

CONCLUSIONS

In this small randomized controlled trial that was stopped for futility before reaching the required sample size, transabdominal and transperineal ultrasound performed just before instrumental vaginal delivery did not reduce the incidence of adverse maternal and neonatal outcomes, when compared with routine clinical care.

Transperineal ultrasound of fetal head progression in prolonged labor: women’s acceptance and ability to predict the mode of delivery

Background

Digital transvaginal examination of fetal head progression is subjective evaluation with many limitations. Using ultrasound (US) in the assessment of labor progression in prolonged labor is the current trend to predict the mode of delivery. The study intends to evaluate the women’s acceptance to the transperineal ultrasound (TPUS) compared with digital transvaginal examination, and its ability to predict the mode of delivery in prolonged labor. We included 28 pregnant ladies in a prolonged active phase of first or second stages of labor and followed them till delivery. TPUS was used to measure the fetal head–perineum distance (FHPD) and the angle of fetal head descent.

Results

Of the 28 participants, 53.5% of them delivered vaginally and 46.5% by Cesarean section (CS). All pregnant ladies described the TPUS as more convenient and less painful than digital vaginal examination. Cervical dilatation was negatively correlated with FHPD, and positively correlated with angle of fetal head descent. Both FHPD and angle of fetal head descent had a strong significant negative correlation. Using a cutoff value of 115° for the angle of fetal head descent, the positive predictive value (PPV) of vaginal delivery was 87%; using a cutoff value of 4.2 cm for FHPD, the PPV for vaginal delivery was 85%.

Conclusion

TPUS is more convenient, more accepted, and less painful than digital vaginal examination. Angle of head descent and FHPD are reliable predictors of the mode of delivery in prolonged labor.

Ultrasound before operative vaginal delivery: why and how

Safe management of the second stage of labor is important. Wait for spontaneous delivery, operative vaginal deliveries and second stage cesarean sections are all options when prolonged second stage occurs. The important question is which option to choose. Fetal head station and fetal head position are used to decide mode of delivery; this has traditionally been decided by performing a digital vaginal examination. Studies have shown that theses clinical examinations of both fetal head station and position are unreliable and that ultrasound might be better option. The International Society of Ultrasound in Obstetrics and Gynecology (ISUOG) published in 2018 guidelines on intrapartum ultrasound and recommends that ultrasound is performed for ascertainment of fetal head position and station before considering or performing an instrumental vaginal delivery for slow progress or arrested labor in the second stage. The determination of the fetal head position, fetal head station and the movement of the fetal head can easily be determined with the help of ultrasound and can help the clinicians in making the right decision on how to proceed when prolonged second stage of labor is diagnosed.

Transperineal ultrasound assessment of maternal pelvic floor at term and fetal head engagement

OBJECTIVES

To evaluate the association between pelvic floor dimensions in nulliparous women at term and fetal head engagement, as assessed by transperineal ultrasound.

METHODS

This was a prospective observational study of nulliparous women at term. Before the onset of labor, transperineal ultrasound was used to measure the anteroposterior diameter (APD) of the levator hiatus and the angle of progression (AoP) at rest, on maximum pelvic floor muscle contraction and on maximum Valsalva maneuver (before and after visual feedback). We assessed the correlation between pelvic floor static and dynamic dimensions (levator hiatal APD and levator ani muscle coactivation) and AoP, which is an objective index of fetal head engagement.

RESULTS

In total, 282 women were included in the analysis. Among these, 211 (74.8%) women had a vaginal delivery while 71 (25.2%) had a Cesarean delivery. AoP was narrower in the Cesarean-delivery group at rest, on maximum pelvic floor muscle contraction and on maximum Valsalva, whereas no differences in levator hiatal APD were found between the two groups. We found a negative correlation between levator hiatal APD at rest, on maximum pelvic floor muscle contraction and on maximum Valsalva and the duration of the second stage of labor. There was a positive correlation between AoP and levator hiatal APD on maximum Valsalva maneuver after visual feedback (r = 0.15, P = 0.01). Women with levator ani muscle contraction on Valsalva maneuver (i.e. coactivation), both pre and post visual feedback, had a narrower AoP at rest and on maximum Valsalva. After visual feedback, women with levator ani muscle coactivation had a longer second stage of labor than did those without (80.8 ± 61.4 min vs 62.9 ± 43.4 min (P = 0.04)).

CONCLUSIONS

Smaller pelvic floor dimensions and levator ani muscle coactivation are associated with higher fetal head station and with a longer second stage of labor in nulliparous women at term. Copyright © 2020 ISUOG. Published by John Wiley & Sons Ltd.

Intrapartum ultrasound at the initiation of the active second stage of labor predicts spontaneous vaginal delivery

BACKGROUND

Longer duration of active pushing during labor is associated with a higher rate of operative delivery and an increased risk of maternal and neonatal complications. Although immediate pushing at complete dilatation is associated with lower rates of chorioamnionitis and postpartum hemorrhage, it is also associated with a longer duration of pushing.

OBJECTIVE

This study aimed to evaluate whether fetal head station and position, as assessed by ultrasound at the beginning of the pushing process, can predict the mode of delivery and duration of pushing in nulliparous women.

STUDY DESIGN

This prospective observational study included nulliparous women with neuraxial analgesia and complete cervical dilatation. The following sonographic parameters were assessed just before the beginning of the pushing process, at rest, and while pushing during contraction: head position, angle of progression, head-perineum distance, and head-symphysis distance. The change between rest and pushing was designated as delta angle of progression, delta head-perineum distance, and delta head-symphysis distance. The sonographic measurements and fetal head station assessed by vaginal examination were compared between women who had a spontaneous vaginal delivery to those who underwent an operative delivery, and between those who pushed for more or less than 1 hour.

RESULTS

Of the 197 women included in this study, 166 (84.3%) had a spontaneous vaginal delivery, 31 (15.7%) had an operative delivery, 23 (11.6%) had a vacuum delivery, and 8 (4.0%) had a cesarean delivery. Spontaneous vaginal delivery and shorter duration of pushing (less than an hour) were significantly more common with a nonocciput posterior position (10.6% vs 47.3%; P<.005), a wider angle of progression, a shorter head-perineum distance and head-symphysis distance (both during rest and while pushing), and a lower fetal head station as assessed by digital vaginal examination. However, a logistic regression model revealed that only the angle of progression at rest and the delta angle of progression were independently associated with a spontaneous vaginal delivery with an area under the curve of 0.82 (95% confidence interval, 0.76-0.87; P<.0001) and 0.75 (95% confidence interval, 0.67-0.79; P<.0001), respectively.

CONCLUSION

Ultrasound performed at the beginning of the active second stage of labor can assist in predicting the mode of delivery and duration of pushing and perform better than the traditional digital examination, with the angle of progression at rest and delta angle of progression being the best predictors.

New technique for automatic sonographic measurement of change in head-perineum distance and angle of progression during active phase of second stage of labor

OBJECTIVE

To evaluate the performance of a new ultrasound technique for the automatic assessment of the change in head-perineum distance (delta-HPD) and angle of progression (delta-AoP) during the active phase of the second stage of labor.

METHODS

This was a prospective observational cohort study including singleton term pregnancies with fetuses in cephalic presentation during the active phase of the second stage of labor. In each patient, two videoclips of 10 s each were acquired transperineally, one in the axial and one in the sagittal plane, between rest and the acme of an expulsive effort, in order to measure HPD and AoP, respectively. The videoclips were processed offline and the difference between the acme of the pushing effort and rest in HPD (delta-HPD) and AoP (delta-AoP) was calculated, first manually by an experienced sonographer and then using a new automatic technique. The reliability of the automatic algorithm was evaluated by comparing the automatic measurements with those obtained manually, which was considered as the reference gold standard.

RESULTS

Overall, 27 women were included. A significant correlation was observed between the measurements obtained by the automatic and the manual methods for both delta-HPD (intraclass correlation coefficient (ICC) = 0.97) and delta-AoP (ICC = 0.99). The high accuracy provided by the automatic algorithm was confirmed by the high values of the coefficient of determination (r²  = 0.98 for both delta-HPD and delta-AoP) and the low residual errors (root mean square error = 1.2 mm for delta-HPD and 1.5° for delta-AoP). A Bland-Altman analysis showed a mean difference of 0.52 mm (limits of agreement, -1.58 to 2.62 mm) for delta-HPD (P = 0.034) and 0.35° (limits of agreement, -2.54 to 3.09°) for delta-AoP (P = 0.39) between the manual and automatic measurements.

CONCLUSIONS

The automatic assessment of delta-AoP and delta-HPD during maternal pushing efforts is feasible. The automatic measurement of delta-AoP appears to be reliable when compared with the gold standard manual measurement by an experienced operator. Copyright © 2020 ISUOG. Published by John Wiley & Sons Ltd.

Evaluation of the labour process with serial transperineal ultrasonography and prediction of the type of birth

OBJECTIVES

The purpose of this study is to follow the birth process with transperineal ultrasonography (TPU) and predict the delivery method using angle of progression (AOP).

METHODS

The study included 134 patients. The AOP was examined with TPU in the lithotomy position applied at 4-h intervals, not at a time of straining or contractions. The relationship was examined between AOP and those who continued with vaginal delivery, and those who underwent caesarean section delivery.

RESULTS

A total of 122 (91%) patients had vaginal delivery and 12 (9%) patients had cesarean delivery. In patients giving vaginal delivery, progress in AOP was observed in every 4-h measurement, but not in patients with cesarean section. In the ROC analysis, if 70% sensitivity and 75% specificity with AOP degree >132.5°, the patient was expected to have vaginal delivery with a probability of 77.5% (95% CI 0.62-0.93; p=0.002).

CONCLUSIONS

Rather than repeating digital examinations, the labour process can be monitored with serial TPU and the type of delivery can be predicted. There is a need for further studies for the measurement of AOP with TPU to become a part of clinical practice in the monitoring of the whole labour process.

Automatic measurement of head-perineum distance during intrapartum ultrasound: description of the technique and preliminary results

OBJECTIVES

To evaluate the accuracy and reliability of a new ultrasound technique for the automatic assessment of the head-perineum distance (HPD) during childbirth.

METHODS

HPD was measured on a total of 40 acquisition sessions in 30 laboring women both automatically by an innovative algorithm and manually by trained sonographers, assumed as gold standard.

RESULTS

A significant correlation was found between manual and automatic measurements (Intra-CC = 0.994). High values of the coefficient of determination (r²=0.98) and low residual errors: RMSE = 2.01 mm (4.9%) were found.

CONCLUSION

The automatic algorithm for the assessment of the HPD represents a reliable technique.

Can assessing the angle of progression before labor onset assist to predict vaginal birth after cesarean?: A prospective cohort observational study

Objective: To assess whether pre-labor measurement of the angle of progression (AOP) can assist in predicting a successful vaginal birth after cesarean in women without a previous vaginal birth.Methods: A prospective observational cohort study performed in a single tertiary center including women at term with a single previous cesarean delivery (CD), without prior vaginal births, who desire a trial of labor. Transperineal ultrasound was used to measure the AOP before the onset of labor. The managing staff in the delivery suite was blinded to the ultrasound measurements. Clinical data and delivery outcome were retrieved from medical records. The study was approved by the institutional ethics committee (KMC 0117-10).Results: Of the 111 women included in the study, 67 (60.4%) had a successful vaginal birth after CD. Women were sonographically assessed at a median of 3 days [interquartile range (IQR) 1-3 days] prior to delivery. The median AOP was significantly narrower in women who eventually underwent a CD than in those who delivered vaginally (88°, IQR 78-96° vs. 99°, IQR 89-107°, respectively; p < .001). An AOP >98° (derived from a receiver operating characteristic curve) was associated with a successful vaginal birth after CD in 87.5% of women. Multivariable regression analysis demonstrated that each additional 1° in the AOP increases the chance for a successful vaginal birth after CD by 6%.Conclusions: Pre-labor AOP may be a useful sonographic tool for predicting vaginal birth after CD and can assist in consulting primiparous women with a prior CD opting for a trial of labor.

Comparison of different methods of measuring angle of progression in prediction of labor outcome

OBJECTIVES

First, to compare the manual sagittal and parasagittal and automated parasagittal methods of measuring the angle of progression (AoP) by transperineal ultrasound during labor, and, second, to develop models for the prediction of time to delivery and need for Cesarean section (CS) for failure to progress (FTP) in a population of patients undergoing induction of labor.

METHODS

This was a prospective observational study of transperineal ultrasound in a cohort of 512 women with a singleton pregnancy undergoing induction of labor. A random selection of 50 stored images was assessed for inter- and intraobserver reliability of AoP measurements using the manual sagittal and parasagittal and automated parasagittal methods. In cases of vaginal delivery, univariate linear, multiple linear and quantile regression analyses were performed to predict time to delivery. Univariate and multivariate binomial logistic regression analyses were performed to predict CS for FTP in the first stage of labor.

RESULTS

The intraclass correlation coefficient (ICC) for the manual parasagittal method for a single observer was 0.97 (95% CI, 0.95-0.98) and for two observers it was 0.96 (95% CI, 0.93-0.98), indicating good reliability. The ICC for the sagittal method for a single observer was 0.93 (95% CI, 0.88-0.96) and for two observers it was 0.74 (95% CI, 0.58-0.84), indicating moderate reliability for a single observer and poor reliability between two observers. Bland-Altman analysis demonstrated narrower limits of agreement for the manual parasagittal approach than for the sagittal approach for both a single and two observers. The automated parasagittal method failed to capture an image in 19% of cases. The mean difference in AoP measurements between the sagittal and manual parasagittal methods was 11°. In pregnancies resulting in vaginal delivery, 54% of the variation in time to delivery was explained in a model combining parity, epidural and syntocinon use during labor and the sonographic findings of fetal head position and AoP. In the prediction of CS for FTP in the first stage of labor, a model which combined maternal factors with the sonographic measurements of AoP and estimated fetal weight was superior to one utilizing maternal factors alone (area under the receiver-operating-characteristics curve, 0.80 vs 0.76).

CONCLUSIONS

First, the method of measuring AoP with the greatest reliability is the manual parasagittal technique and future research should focus on this technique. Second, over half of the variation in time to vaginal delivery can be explained by a model that combines maternal factors, pregnancy characteristics and ultrasound findings. Third, the ability of AoP to provide clinically useful prediction of CS for FTP in the first stage of labor is limited. Copyright © 2019 ISUOG. Published by John Wiley & Sons Ltd.

Using transperineal ultrasound to predict labor onset

Background

Accurate diagnosis of labor onset is especially important for the counseling about elective induction of labor. The study aimed to evaluate whether transperineal ultrasound could better predict the timing and likelihood of spontaneous labor at term.

Methods

This single-center study was conducted between 2018 and 2019.Data on singleton pregnant women after 39 weeks and before labor onset were retrospectively reviewed.

Results

All the transperineal ultrasound parameters were well reproducible between the two doctors [intraclass correlation coefficient (ICC) for progression distance(PD) was 0.892, P<0.001], [ICC for angle of progression (AoP) was 0.881, P<0.001], [ICC for subpubic arch angle (SPA) was 0.766, P<0.001], [ICC for width of symphysis pubis (WSP) was 0.803, P<0.001]. For the pregnant women before 40 weeks, the width of symphysis pubis changed gradually with the of spontaneous labor (WSP) (r=0.33, P<0.05). For all included women, the SPA correlated with the time of spontaneous labor (SPA) (r=0.31, P<0.05).

Conclusions

The antepartum transperineal ultrasound is a simple and objective technique that better observes the initiation of labor. And with the WSP and SPA we were able to predict labor onset and help in counseling about elective induction of labor.

Prediction of spontaneous vaginal delivery in nulliparous women with a prolonged second stage of labor: the value of intrapartum ultrasound

BACKGROUND

A limited number of studies have addressed the role of intrapartum ultrasound in the prediction of the mode of delivery in women with prolonged second stage of labor.

OBJECTIVE

The objective of the study was to evaluate the role of transabdominal and transperineal sonographic findings in the prediction of spontaneous vaginal delivery among nulliparous women with prolonged second stage of labor.

STUDY DESIGN

This was a 2-center prospective study conducted at 2 tertiary maternity units. Nulliparous women with a prolonged active second stage of labor, as defined by active pushing lasting more than 120 minutes, were eligible for inclusion. Transabdominal ultrasound to evaluate the fetal head position and transperineal ultrasound for the measurement of the midline angle, the head-perineum distance, and the head-symphysis distance were performed in between uterine contractions and maternal pushes. At transperineal ultrasound the angle of progression was measured at rest and at the peak of maternal pushing effort. The delta angle of progression was defined as the difference between the angle of progression measured during active pushing at the peak of maternal effort and the angle of progression at rest. The sonographic findings of women who had spontaneous vaginal delivery vs those who required obstetric intervention, either vacuum extraction or cesarean delivery, were evaluated and compared.

RESULTS

Overall, 109 were women included. Spontaneous vaginal delivery and obstetric intervention were recorded in 40 (36.7%) and 69 (63.3%) patients, respectively. Spontaneous vaginal delivery was associated with a higher rate of occiput anterior position (90% vs 53.2%, P < .0001), lower head-perineum distance and head-symphysis distance (33.2 ± 7.8 mm vs 40.1 ± 9.5 mm, P = .001, and 13.1 ± 4.6 mm vs 19.5 ± 8.4 mm, P < .001, respectively), narrower midline angle (29.6° ± 15.3° vs 54.2° ± 23.6°, P < .001) and wider angle of progression at the acme of the pushing effort (153.3° ± 19.8° vs 141.8° ± 25.7°, P = .02) and delta-angle of progression (17.3° ± 12.9° vs 12.5° ± 11.0°, P = .04). At logistic regression analysis, only the midline angle and the head-symphysis distance proved to be independent predictors of spontaneous vaginal delivery. More specifically, the area under the curve for the prediction of spontaneous vaginal delivery was 0.80, 95% confidence interval (0.69-0.92), P < .001, and 0.74, 95% confidence interval (0.65-0.83), P = .002, for the midline angle and for the head-symphysis distance, respectively.

CONCLUSION

Transabdominal and transperineal intrapartum ultrasound parameters can predict the likelihood of spontaneous vaginal delivery in nulliparous women with prolonged second stage of labor.

Reliability of transperineal ultrasound for the assessment of the angle of progression in labor using parasagittal approach versus midsagittal approach

OBJECTIVE

To assess the inter-method agreement between midsagittal (msAoP) and parasagittal (psAoP) measurements of the angle of progression (AoP) during labor. In addition, we aimed to evaluate the correlation between AoP measurements by both midsagittal and parasagittal approaches with the mode of delivery.

METHODS

We recruited a nonconsecutive series of women in active labor with a singleton uncomplicated term pregnancy with fetuses in vertex presentation. Women underwent transperineal ultrasound in the absence of uterine contractions or maternal pushing to measure both msAoP and psAoP. The inter-method agreement between the two acquisitions was then assessed. Lastly, both measurements were compared between women who had a vaginal delivery versus those who underwent cesarean section (CS).

RESULTS

Overall, 151 women were included in the study. We found an excellent agreement between msAoP and psAoP (ICC 0.935; 95% CI 0.912-0.953, p < .001). On the other hand, psAoP overestimated the measurements in comparison with msAoP (101.2 ± 15.6 versus 98.2 ± 16.0, p < .001). There was a significant correlation between both methods of AoP assessment and duration of the active second stage of labor and AoP measured by either method was significantly wider in patients who delivered vaginally compared to those who had a CS.

CONCLUSIONS

Our data showed a significant difference in the measured angle between the psAoP and the originally described msAoP. The automated measurements of AoP that have been introduced are designed using the parasagittal visualization of the more echogenic pubic arch, rather than the hypoechogenic pubic symphysis. We think that in the light of our data, care should be taken before applying data from midsagittal measurement in centers using the parasagittal automated approach.

Can the Progression Angle before Labor Help to Predict Cesarean Section?

OBJECTIVE

The aim of this study was to predict cesarean section on a single visit at term using a combination of maternal history and ultrasound markers, including some new markers such as the progression angle used to assess intrapartum progress.

STUDY DESIGN

This was an observational prospective cohort study of singleton term pregnancies that included 575 women. The maternal history and ultrasound markers were obtained on a single visit at 37-38 weeks' gestation. Multivariable logistic regression was used for prediction of cesarean section.

RESULTS

Five hundred and seventy-five women were examined at a median gestational age of 38.3 weeks (range: 35.6-41.6) and a cesarean section was performed on 104 women (18%) - 24 for a fetal indication and 80 for a maternal indication. The risk of cesarean section increased with a previous cesarean section, assisted reproduction techniques, a higher estimated fetal weight, and a greater cervical length, and decreased with a greater maternal height, multiparity, and a wider progression angle. The detection rate for a 20% false positive rate was 69.9% for all cesarean sections, 54.2% for those with a fetal indication, and 77.2% for those with a maternal indication.

CONCLUSIONS

Assessment at 37-38 weeks' gestation of ultrasound markers such as the cervical length, progression angle, and estimated fetal weight, in combination with the maternal history, can predict a cesarean section in labor. Cesarean section for a maternal indication is better predicted than cesarean section for a fetal indication.