Prediction of labor outcome using serial transperineal ultrasound in the first stage of labor

The use of bubble charts in analyzing second stage cesarean delivery rates

BACKGROUND

The incidence of second stage cesarean delivery has been rising globally because of the failure or the anticipated difficulty of performing instrumental delivery. Yet, the best way to interpret the figure and its optimal rate remain to be determined. This is because it is strongly influenced by the practice of other 2 modes of birth, namely cesarean delivery performed before reaching the second stage and assisted vaginal birth during the second stage. In this regard, a bubble chart that can display 3-dimensional data through its x-axis, y-axis, and the size of each plot (presented as a bubble) may be a suitable method to evaluate the relationship between the rates of these 3 modes of births.

OBJECTIVE

This study aimed to conduct an epidemiologic study on the incidence of second stage cesarean deliveries rates among >300,000 singleton term births in 10 years from 8 obstetrical units and to compare their second stage cesarean delivery rates in relation to their pre-second stage cesarean delivery rates and assisted vaginal birth rates using a bubble chart.

STUDY DESIGN

The territory-wide birth data collected between 2009 and 2018 from all 8 public obstetrical units (labelled as A to H) were reviewed. The inclusion criteria were all singleton pregnancies with cephalic presentation that were delivered at term (≥37 weeks' gestation). Pre-second stage cesarean delivery rate was defined as all elective cesarean deliveries and those emergency cesarean deliveries that occurred before full cervical dilatation was achieved as a proportion of the total number of births. The second stage cesarean delivery rate and assisted vaginal birth rate were calculated according to the respective mode of delivery as a proportion of the number of cases that reached full cervical dilatation. The rates of these 3 modes of births were compared among the parity groups and among the 8 units. Using a bubble chart, each unit's second stage cesarean delivery rate (y-axis) was plotted against its pre-second stage cesarean delivery rate (x-axis) as a bubble. Each unit's second stage cesarean delivery to assisted vaginal birth ratio was represented by the size of the bubble.

RESULTS

During the study period, a total of 353,434 singleton cephalic presenting term pregnancies were delivered in the 8 units, and 180,496 (51.1%) were from nulliparous mothers. When compared with the multiparous group, the nulliparous group had a significantly lower pre-second stage cesarean delivery rate (18.58% vs 21.26%; P<.001) but a higher second stage cesarean delivery rate (0.79% vs 0.22%; P<.001) and a higher assisted vaginal birth rate (17.61% vs 3.58%; P<.001). Using the bubble of their averages as a reference point in the bubble chart, the 8 units' bubbles were clustered into 5 regions indicating their differences in practice: unit B and unit H were close to the average in the center. Unit A and unit F were at the upper right corner with a higher pre-second stage cesarean delivery rate and second stage cesarean delivery rate. Unit D and unit E were at the opposite end. Unit C was at the upper left corner with a low pre-second stage cesarean delivery rate but a high second stage cesarean delivery rate, whereas unit G was at the opposite end. Unit C and unit G were also in the extremes in terms of pre-second stage cesarean delivery to assisted vaginal birth ratio (0.09 and 0.01, respectively). Although some units seemed to have very similar second stage cesarean delivery rates, their obstetrical practices were differentiated by the bubble chart.

CONCLUSION

The second stage cesarean delivery rate must be evaluated in the context of the rates of pre-second stage cesarean delivery and assisted vaginal birth. A bubble chart is a useful method for analyzing the relationship among these 3 variables to differentiate the obstetrical practice between different units.

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.

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.

Intrapartum ultrasound for fetal head asynclitism: Is it possible to establish a degree of asynclitism to correlate to delivery outcome?

OBJECTIVE

To investigate the role of intrapartum ultrasound (IU) in the diagnosis of asynclitism and the importance of asynclitism degree in labor outcomes.

METHOD

This prospective cohort study included 41 low-risk pregnant women with fetus in singleton-vertex. The IU assessment to diagnose asynclitism was performed during labor at two specific steps, including the suspicion and/or diagnosis of labor arrest. The "four-chamber view" and "squint sign without nose" were classified as marked/severe asynclitism. The "midline deviation" and "squint sign with nose" findings were classified as moderate asynclitism. Obstetric outcomes and maternal-fetal complications were compared with the degree of asynclitism.

RESULTS

Severe and moderate asynclitism was seen in 17 (41.7%), 10 (58.8%) and seven (41.2%) women, respectively. All pregnant women diagnosed with asynclitism delivered by vacuum extraction (VE) or cesarean section (CS). CS was performed in nine patients with asynclitism (52.9%). The difference between asynclitism type and VE/CS ratios was statistically significant (P = 0.039). Four fetuses with squint sign without nose delivered by VE. A significant correlation was seen between the presence of squint without nose sign and second-/third-degree perineal injury.

CONCLUSION

Severe asynclitism is associated with increasing operative birth and maternal-fetal complications. Detection of asynclitism degree by IU could be useful, alerting the obstetrics team to possible perinatal problems during delivery.

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.

Accuracy of non-invasive methods for assessing the progress of labor in the first stage: a systematic review and meta-analysis

Background

The World Health Organization in recent years has emphasized reducing the possibility of unnecessary interventions in natural childbirth, but little is known about the accuracy of non-invasive methods when assessing the progress of labor. This paper presents a literature review to assess strategies that support non-invasive methods for labor during the first stage. It evaluates the available evidence to provide the most suitable assessments and predictions that objectively identify the progress of low-risk labor during the first stage of labor.

Methods

A search for relevant literature was conducted using the electronic databases of PubMed, CINAHL, Web of Sciences, the Cochrane Library, Scopus, Medline (OVID), and CEPS, with publications up to November 2021. Records were screened against pre-specified inclusion/exclusion criteria and the potential papers from Google Scholar were examined to identify additional papers that may have been missed. The Quality Assessment of Diagnostic Accuracy Studies-2 (QUADAS-2) tool was used to appraise the methodological quality of the included studies. The certainty of the evidence was assessed using the Grading of Recommendations Assessment, Development, and Evaluation (GRADE) approach. Two independent investigators extracted the review’s characteristics, and discrepancies were resolved by consensus. This review calculated individual and pooled sensitivity, specificity, and positive predictive values, which were exported to STATA (version 14; Stata Corp., College Station, TX) to represent the performance of diagnostic testing.

Results

Our search returned 2283 reports of which 13 fulfilled the inclusion criteria, accounting for 2594 women. The subjects were divided into groups according to the diagnostic tests used to assess the progress of their labor, including appearance assessment and sonographic imaging parameters (head perineum distance, HPD; angle of progression, AOP, and other parameters). HPD pooled sensitivity was 0.74 (0.65–0.82), and specificity was 0.77 (0.69–0.84). The pooled diagnostic odds ratio (DOR) was 8.21 (4.67–14.41) and 10.34 (5.02–21.27), respectively. The results of subgroup analysis showed that the summary sensitivity and specificity were of medium accuracy overall. The quality of evidence as assessed with GRADE was low.

Conclusion

Vaginal examination is an intrinsic element in the use of the partogram, while transperineal ultrasound can also be used as an auxiliary tool. However, the presence of publication bias within the parameters of ultrasound indicates that the diagnostic performance may be overestimated. Thus, randomized controlled trials or large-scale prospective cohort studies are necessary.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12884-022-04938-y.

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.

Transperineal ultrasound assessment of fetal head elevation by maneuvers used for managing umbilical cord prolapse

OBJECTIVE

To assess objectively the degree of fetal head elevation achieved by different maneuvers commonly used for managing umbilical cord prolapse.

METHODS

This was a prospective observational study of pregnant women at term before elective Cesarean delivery. A baseline assessment of fetal head station was performed with the woman in the supine position, using transperineal ultrasound for measuring the parasagittal angle of progression (psAOP), head-symphysis distance (HSD) and head-perineum distance (HPD). The ultrasonographic measurements of fetal head station were repeated during different maneuvers, including elevation of the maternal buttocks using a wedge, knee-chest position, Trendelenburg position with a 15° tilt and filling the maternal urinary bladder with 100 mL, 300 mL and 500 mL of normal saline. The measurements obtained during the maneuvers were compared with the baseline measurements.

RESULTS

Twenty pregnant women scheduled for elective Cesarean section at term were included in the study. When compared with baseline (median psAOP, 103.6°), the knee-chest position gave the strongest elevation effect, with the greatest reduction in psAOP (psAOP, 80.7°; P < 0.001), followed by filling the bladder with 500 mL (psAOP, 89.9°; P < 0.001) and 300 mL (psAOP, 94.4°; P < 0.001) of normal saline. Filling the maternal bladder with 100 mL of normal saline (psAOP, 96.1°; P = 0.001), the Trendelenburg position (psAOP, 96.8°; P = 0.014) and elevating the maternal buttocks (psAOP, 98.3°; P = 0.033) gave modest elevation effects. Similar findings were reported for HSD and HPD. The fetal head elevation effects of the knee-chest position, Trendelenburg position and elevation of the maternal buttocks were independent of the initial fetal head station, but that of bladder filling was greater when the initial head station was low.

CONCLUSIONS

To elevate the fetal presenting part, the knee-chest position provides the best effect, followed by filling the maternal urinary bladder with 500 mL then 300 mL of fluid, respectively. Filling the bladder with 100 mL of fluid, the Trendelenburg position and elevation of the maternal buttocks have modest effects. © 2020 International Society of Ultrasound in Obstetrics and Gynecology.

Intrapartum ultrasound in women with prolonged first stage of labor

The first stage of labor is from the start of active labor until the cervix is fully dilatated. To assess labor progress during this stage, a clinical examination has traditionally been done. The cervical dilatation, fetal head position, and fetal head station are evaluated. Moreover, these observations can be made with an ultrasound examination. Studies have shown that traditional clinical examinations are subjective, have poor reproducibility, and are unreliable. Ultrasound examinations of the fetal head station and fetal head position in the first stage of labor might predict labor outcome and mode of delivery and can help in decision making when prolonged first stage of labor is diagnosed.

Can ultrasound on admission in active labor predict labor duration and a spontaneous delivery?

BACKGROUND

Identifying predictive factors for a normal outcome at admission in the labor ward would be of value for planning labor care, timing interventions, and preventing labor dystocia. Clinical assessments of fetal head station and position at the start of labor have some predictive value, but the value of ultrasound methods for this purpose has not been investigated. Studies using transperineal ultrasound before labor onset show possibilities of using these methods to predict outcomes.

OBJECTIVE

This study aimed to investigate whether ultrasound measurements during the first examination in the active phase of labor were associated with the duration of labor phases and the need for operative delivery.

STUDY DESIGN

This was a secondary analysis of a prospective cohort study at Landspitali University Hospital, Reykjavík, Iceland. Nulliparous women at ≥37 weeks' gestation with a single fetus in cephalic presentation and in active spontaneous labor were eligible for the study. The recruitment period was from January 2016 to April 2018. Women were examined by a midwife on admission and included in the study if they were in active labor, which was defined as regular contractions with a fully effaced cervix, dilatation of ≥4 cm. An ultrasound examination was performed by a separate examiner within 15 minutes; both examiners were blinded to the other's results. Transabdominal and transperineal ultrasound examinations were used to assess fetal head position, cervical dilatation, and fetal head station, expressed as head-perineum distance and angle of progression. Duration of labor was estimated as the hazard ratio for spontaneous delivery using Kaplan-Meier curves and Cox regression analysis. The hazard ratios were adjusted for maternal age and body mass index. The associations between study parameters and mode of delivery were evaluated using receiver operating characteristic curves.

RESULTS

Median times to spontaneous delivery were 490 minutes for a head-perineum distance of ≤45 mm and 682 minutes for a head-perineum distance of >45 mm (log-rank test, P=.009; adjusted hazard ratio for a shorter head-perineum distance, 1.47 [95% confidence interval, 0.83-2.60]). The median durations were 506 minutes for an angle of progression of ≥93° and 732 minutes for an angle of progression of <93° (log-rank test, P=.008; adjusted hazard ratio, 2.07 [95% confidence interval, 1.15-3.72]). The median times to delivery were 506 minutes for nonocciput posterior positions and 677 minutes for occiput posterior positions (log-rank test, P=.07; adjusted hazard ratio, 1.52 [95% confidence interval, 0.96-2.38]) Median times to delivery were 429 minutes for a dilatation of ≥6 cm and 704 minutes for a dilatation of 4 to 5 cm (log-rank test, P=.002; adjusted hazard ratio, 3.11 [95% confidence interval, 1.68-5.77]). Overall, there were 75 spontaneous deliveries; among those deliveries, 16 were instrumental vaginal deliveries (1 forceps delivery and 15 ventouse deliveries), and 8 were cesarean deliveries. Head-perineum distance and angle of progression were associated with a spontaneous delivery with area under the receiver operating characteristic curves of 0.68 (95% confidence interval, 0.55-0.80) and 0.67 (95% confidence interval, 0.55-0.80), respectively. Ultrasound measurement of cervical dilatation or position at inclusion was not significantly associated with spontaneous delivery.

CONCLUSION

Ultrasound examinations showed that fetal head station and cervical dilatation were associated with the duration of labor; however, measurements of fetal head station were the variables best associated with operative deliveries.

Fetal descent in nulliparous women assessed by ultrasound: a longitudinal study

BACKGROUND

Ultrasound measurements offer objective and reproducible methods to measure the fetal head station. Before these methods can be applied to assess labor progression, the fetal head descent needs to be evaluated longitudinally in well-defined populations and compared with the existing data derived from clinical examinations.

OBJECTIVE

This study aimed to use ultrasound measurements to describe the fetal head descent longitudinally as labor progressed through the active phase in nulliparous women with spontaneous onset of labor.

STUDY DESIGN

This was a single center, prospective cohort study at the Landspitali - The National University Hospital of Iceland, Reykjavik, Iceland, from January 2016 to April 2018. Nulliparous women with a single fetus in cephalic presentation and spontaneous labor onset at a gestational age of ≥37 weeks, were eligible. Participant inclusion occurred during admission for women with an established active phase of labor or at the start of the active phase for women admitted during the latent phase. The active phase was defined as an effaced cervix dilated to at least 4 cm in women with regular contractions. According to the clinical protocol, vaginal examinations were done at entry and subsequently throughout labor, paired each time with a transperineal ultrasound examination by a separate examiner, with both examiners being blinded to the other's results. The measurements used to assess the fetal head station were the head-perineum distance and angle of progression. Cervical dilatation was examined clinically.

RESULTS

The study population comprised 99 women. The labor patterns for the head-perineum distance, angle of progression, and cervical dilatation differentiated the participants into 75 with spontaneous deliveries, 16 with instrumental vaginal deliveries, and 8 cesarean deliveries. At the inclusion stage, the cervix was dilated 4 cm in 26 of the women, 5 cm in 30 of the women, and ≥6 cm in 43 women. One cesarean and 1 ventouse delivery were performed for fetal distress, whereas the remaining cesarean deliveries were conducted because of a failure to progress. The total number of examinations conducted throughout the study was 345, with an average of 3.6 per woman. The ultrasound-measured fetal head station both at the first and last examination were associated with the delivery mode and remaining time of labor. In spontaneous deliveries, rapid head descent started around 4 hours before birth, the descent being more gradual in instrumental deliveries and absent in cesarean deliveries. A head-perineum distance of 30 mm and angle of progression of 125° separately predicted delivery within 3.0 hours (95% confidence interval, 2.5-3.8 hours and 2.4-3.7 hours, respectively) in women delivering vaginally. Although the head-perineum distance and angle of progression are independent methods, both methods gave similar mirror image patterns. The fetal head station at the first examination was highest for the fetuses in occiput posterior position, but the pattern of rapid descent was similar for all initial positions in spontaneously delivering women. Oxytocin augmentation was used in 41% of women; in these labors a slower descent was noted. Descent was only slightly slower in the 62% of women who received epidural analgesia. A nonlinear relationship was observed between the fetal head station and dilatation.

CONCLUSION

We have established the ultrasound-measured descent patterns for nulliparous women in spontaneous labor. The patterns resemble previously published patterns based on clinical vaginal examinations. The ultrasound-measured fetal head station was associated with the delivery mode and remaining time of labor.

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.

Feasibility, Reliability, and Agreement of Transperineal Ultrasound Measurement: Results from a Longitudinal Cohort Study

OBJECTIVES

To evaluate the feasibility, reliability, and agreement of serial transperineal ultrasound (TPU) assessment of fetal head station (parasagittal angle of progression [psAOP], head-perineum distance [HPD], and head-symphysis distance [HSD]) and sonographic cervical dilatation (SCD), compared to fetal head station and cervical dilatation determined by vaginal examination, respectively.

METHODS

This was a prospective longitudinal study in singleton pregnancies undergoing induction of labor at term. Paired assessment of fetal head station and cervical dilatation by vaginal examination, with TPU assessment of psAOP, HPD, HSD, and SCD was made serially. Feasibility, correlation, reliability, and agreement were determined.

RESULTS

1,139 paired measurements among 326 women were included. psAOP and HPD were achievable in all assessments. HSD was not achievable in 3.4% (11/326) due to high fetal head station. Fetal head station by vaginal examination was positively correlated with psAOP (rho = 0.70) but negatively correlated with HPD (rho = -0.57) and HSD (rho = -0.52). The feasibility to measure SCD reduced as cervical dilatation increased. Cervical dilatation and SCD were positively correlated (rho = 0.96) with strong agreement (concordant correlation coefficient = 0.925).

CONCLUSIONS

Measurements of psAOP and HPD are feasible and correlate significantly with fetal head station by vaginal examination. Measurement of HSD is not feasible when fetal head station is high. Measurement of SCD is feasible, but it is more difficult in the advanced stage of labor. The correlation, reliability, and agreement between SCD and cervical dilatation by vaginal examination are high.

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.

Labor progress determined by ultrasound is different in women requiring cesarean delivery from those who experience a vaginal delivery following induction of labor

BACKGROUND

The diagnosis of labor dystocia generally is determined by the deviation of labor progress, which is assessed by the use of a partogram. Recently, intrapartum transperineal ultrasound for the assessment of fetal head descent has been introduced to assess labor progress in the first stage of labor in a more objective and noninvasive way.

OBJECTIVE

The objective of the study was to determine the differences in labor progress by the use of serial transperineal ultrasound assessment of fetal head descent between women having vaginal and cesarean delivery.

STUDY DESIGN

This was a prospective longitudinal study performed in 315 women with singleton pregnancy who were undergoing labor induction at term between December 2016 and December 2017. Paired assessment of cervical dilation and fetal head station by vaginal examination and transperineal ultrasonographic assessment of parasagittal angle of progression and head-perineum distance were made serially after the commencement of labor induction. According to the hospital protocol, assessment was performed every 24 hours and 4 hours, respectively, during latent and active phases of labor. The researchers and the clinical team were blinded to each other's findings. The repeated measures data were analyzed by mixed effect models. To determine the effect of mode of delivery on the association between parasagittal angle of progression and head-perineum distance against fetal head station and cervical dilation, the significance of the interaction term between each mode of delivery and fetal head station or cervical dilation was determined, which accounted for parity and obesity. Area under receiver-operating characteristic curve was used to evaluate the performance of serial intrapartum sonography in predicting women with cesarean delivery because of failure to progress.

RESULTS

The total number of paired vaginal examination and ultrasound assessments was 1198, with a median of 3 per woman. The median assessment-to-assessment interval was 4.6 hours (interquartile range, 4.3-5.1 hours). Women who achieved vaginal delivery (n=261) had steeper slopes of parasagittal angle of progression and head-perineum distance against fetal head station and cervical dilation than those who achieved cesarean delivery (n=54). Objectively, an additional decrease of 5.11 and 1.37 degrees in parasagittal angle of progression was observed for an unit increase in fetal head station and cervical dilation, respectively, in women who required cesarean delivery (P<.01; P=.01), compared with women who achieved vaginal delivery, after taking account of repeated measures from individuals and confounding factors. The respective additional increases in head-perineum distance for a unit increase in fetal head station and cervical dilation were 0.27 cm (P<.01) and 0.12 cm (P<.01). A combination of maternal characteristics with the temporal changes of parasagittal angle of progression for an unit increase in fetal head station achieved an area under receiver-operating characteristic curve of 0.85 (95% confidence interval, 0.76-0.94), with sensitivity of 79% and specificity of 80%, for the prediction of women who required cesarean delivery because of failure to progress.

CONCLUSION

The differences in labor progress between vaginal and cesarean delivery have been illustrated objectively by serial intrapartum transperineal ultrasonographic assessment of fetal head descent. This tool is potentially predictive of women who will require cesarean delivery because of failure to progress.

Factors that affect ultrasound-determined labor progress in women undergoing induction of labor

BACKGROUND

The traditional approach to the assessment of labor progress is by digital vaginal examination; however, it is subjective and imprecise. Recent studies have investigated the role of transperineal ultrasonographic assessment of fetal head descent by measuring the angle of progression and head-perineum distance.

OBJECTIVE

The objective of this study was to evaluate factors that affected labor progress, which were defined by the transperineal ultrasonographic parameters, in women who achieved vaginal delivery.

STUDY DESIGN

This was a prospective longitudinal study performed in 315 women with singleton pregnancy who underwent labor induction at term between December 2016 and December 2017. Paired assessment of cervical dilation and fetal head station by vaginal examination and transperineal ultrasonographic assessment of fetal head descent (parasagittal angle of progression and head-perineum distance) were made serially after the commencement of labor induction until full cervical dilation. The researchers were blinded to the findings of the clinical team's vaginal examination and vice versa. The repeated measure data were analyzed by mixed effect models to identify the significant factors (age ≥35 years, obesity, parity, methods of labor induction, and epidural anesthesia) that affected the relationship between parasagittal angle of progression and head-perineum distance against fetal head station and cervical dilation.

RESULTS

The total number of paired vaginal examination and transperineal ultrasonographic assessments among the 261 women (82.9%) with vaginal delivery was 945, with a median of 3 per woman. The median assessment-to-assessment interval was 4.6 hours (interquartile range, 4.3-5.2). Multiparity and mechanical methods of labor induction were associated with a faster rate of fetal head descent, which was determined by head-perineum distance against fetal head station, than nulliparity and the use of a slow-release vaginal pessary, respectively. An additional increase of 0.10 cm in head-perineum distance was observed, for an unit increase in fetal head station in nulliparous women (P=.03) and women who had a slow-release vaginal pessary (P=.02), compared with multiparous women and those who had mechanical methods for labor induction. The use of epidural anesthesia was associated with a slower rate of fetal head descent, which was determined by both parasagittal angle of progression and head-perineum distance, against fetal head station. An additional decrease of 3.66 degrees in parasagittal angle of progression (P=.04) and an additional increase in 0.33 cm in head-perineum distance (P≤.001) were observed for a unit increase in fetal head station in women with the use of epidural anesthesia, compared with those without. Obese women had higher head-perineum distance overall, compared with normal weight women; at different cross-sections of time periods, obesity appeared to be associated with a slower rate of change between head-perineum distance and cervical dilation. Advanced maternal age did not affect transperineal ultrasound-determined labor progress (P>.05).

CONCLUSION

Parity, methods of labor induction, the use of epidural anesthesia, and obesity affect labor progress, which has been illustrated objectively by serial transperineal ultrasonographic assessment of fetal head descent.