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

Labour monitoring and decision support: a machine-learning-based paradigm

Introduction

A machine-learning-based paradigm, combining unsupervised and supervised components, is proposed for the problem of real-time monitoring and decision support during labour, addressing the limitations of current state-of-the-art approaches, such as the partograph or purely supervised models.

Methods

The proposed approach is illustrated with World Health Organisation's Better Outcomes in Labour Difficulty (BOLD) prospective cohort study data, including 9,995 women admitted for labour in 2014-2015 in thirteen major regional health care facilities across Nigeria and Uganda. Unsupervised dimensionality reduction is used to map complex labour data to a visually intuitive space. In this space, an ongoing labour trajectory can be compared to those of a historical cohort of women with similar characteristics and known outcomes-this information can be used to estimate personalised "healthy" trajectory references (and alert the healthcare provider to significant deviations), as well as draw attention to high incidences of different interventions/adverse outcomes among similar labours. To evaluate the proposed approach, the predictive value of simple risk scores quantifying deviation from normal progress and incidence of complications among similar labours is assessed in a caesarean section prediction context and compared to that of the partograph and state-of-the-art supervised machine-learning models.

Results

Considering all women, our predictors yielded sensitivity and specificity of ∼0.70. It was observed that this predictive performance could increase or decrease when looking at different subgroups.

Discussion

With a simple implementation, our approach outperforms the partograph and matches the performance of state-of-the-art supervised models, while offering superior flexibility and interpretability as a real-time monitoring and decision-support solution.

2D-transperineal ultrasound in delivery room: Contribution in assessing labor progress, predicting outcome of labor and recognizing obstetric anal sphincter injuries (OASIS). A systematic review

AIMS

Ultrasound is used in the delivery room to assess fetal head position, engagement during labor, and anal sphincter injuries in the immediate postpartum period. The transperineal approach allows for direct visualization of the structures of interest without altering anatomical landmarks. Various ultrasound measurements during labor have been described in the literature, and their use varies widely across maternity units. Our objective was to conduct a systematic review of the literature on relevant ultrasound parameters for the management of labor and delivery.

MATERIAL AND METHODS

We reviewed articles indexed in MEDLINE from 1990 to 2022, selecting those that evaluated transperineal ultrasound during labor for term singleton fetuses in cephalic presentation.

RESULTS

We identified 124 articles out of 394 references, including 4 randomized controlled trials, 108 prospective studies, 6 cross-sectional studies, and 6 retrospective studies. The Angle of Progression (AOP) is better documented and appears more reliable than the Head-Perineum Distance (HPD) for diagnosing engagement, monitoring labor, and predicting its outcome. The HPD is easier to perform but shows inconsistencies in the literature. The Head Progression Distance (HPrD) shows good performance but requires further studies before routine use, as does Head-Symphysis Distance (HSD). Recent studies show a growing interest in ultrasound biofeedback of fetal head progression to improve pushing efforts as well as screening for Obstetrical Anal Sphincter Injuries (OASIS).

CONCLUSIONS

Transperineal ultrasound is a minimally invasive technique that can be used routinely in the delivery room. It can aid in monitoring labor, predicting the mode of delivery, and may serve as valuable biofeedback to optimize pushing during expulsion.

Fetal rotation examined with ultrasound in a sub-Saharan population: A longitudinal cohort study

INTRODUCTION

Occiput posterior (OP) position rates at birth are 5%-8% in studies mainly comprising white European women. The anthropoid pelvis is common in black African women. This pelvic shape has a narrow anterior segment and an ample room posteriorly. The fetal head is wider posteriorly, and the OP position may be favorable in women with an anthropoid pelvic shape. We aimed to examine the fetal rotation with ultrasound longitudinally during the active phase of labor in a sub-Saharan population. We also aimed to examine associations between fetal position, delivery mode, and duration of labor.

MATERIAL AND METHODS

The study was conducted at Kilimanjaro Christian Medical Centre in Moshi, Tanzania from the 19th of November 2023 to 13th of April 2024. Women with a single fetus in cephalic presentation, gestational age >37 weeks, without previous or pre-labor cesarean section were eligible. Fetal position was classified as occiput anterior (OA) from 10 to 2 o'clock, occiput transverse (OT) at 3 or 9 o'clock, and OP position from 4 to 8 o'clock.

RESULTS

The study participants comprised 215 women. Fetal positions at admission, in the first and second stage of labor and at birth are presented in the graphical figure. In all, 65/215 (30.2%) fetuses were in OP position at admission, 59/204 (28.9%) in the first stage, 38/210 (18.1%) in the second stage and 35/215 (16.3%) were delivered in OP position. The OP rates at birth were 25/92 (27.2%) in nulliparous and 10/123 (8.1%) in parous women. The operative delivery rate was 10/157 (6.4%) in women with ultrasound assessed fetal position as OA in the second stage (six cesarean section and four vacuum extractions), and 28/48 (58.3%) in the non-OA group (27 cesarean section and one vacuum extraction) (p < 0.01). The hazard ratio for delivery in the second stage was 0.26 (95% CI 0.13-0.52) for the non-OA vs the OA group in nulliparous women and 0.25 (95% CI 0.12-0.52) in parous women.

CONCLUSIONS

The persistent OP position rate at birth was higher than previously reported, and the operative intervention rate was nine time higher in women with the fetus in non-OA vs OA position in the second stage.

Associations between fetal position at delivery and duration of active phase of labor: A historical cohort study

INTRODUCTION

In clinical experience, occiput posterior (OP) position is associated with longer labor duration than occiput anterior (OA) position, but few studies have investigated the association between labor duration and fetal position. We aimed to compare duration of the active phase of labor in OP deliveries with OA deliveries in a contemporary population using survival methods. Secondary aims were to compare the frequencies of operative interventions, obstetric anal sphincter injuries (OASIS), postpartum hemorrhage, and newborn outcomes in OP with OA deliveries.

MATERIAL AND METHODS

We did a historical cohort study in three university hospitals in Norway from 2012 to 2022. Women with a single fetus in cephalic presentation, no previous cesarean section and gestational age ≥37 weeks were eligible and stratified into the first four groups of the Robson ten-group classification system (TGCS). We estimated the mean duration and calculated the hazard ratio (HR) for delivery using survival analyses. Cesarean sections and instrumental vaginal deliveries were censored.

RESULTS

The study population comprised 112 019 women, 105 571 (94.2%) were delivered in OA and 6448 (5.8%) in OP position. The estimated mean duration of the active phase of labor was longer in women with the fetus in OP position in all four TGCS groups. The estimated duration was longer in the OP groups in analyses stratified with respect to epidural analgesia and oxytocin augmentation. The graphical abstract illustrates the probability of delivery in OP compared with OA position in merged TGCS groups 1 and 2a, as a function of time. The unadjusted HR was 0.33 (95% CI 0.31-0.36) for fetuses delivered in OP position compared with OA position in TGCS group 1, 0.25 (95% CI 0.21-0.27) in group 2a, 0.70 (95% CI 0.67-0.73) in group 3, and 0.61 (95% CI 0.55-0.67) in group 4a, respectively. Neither maternal age, gestational age, BMI nor birthweight had confounding effect. Operative delivery rates and OASIS rates were higher in OP position in all four groups.

CONCLUSIONS

We found longer duration of the active phase of labor in women with the fetus delivered in OP position in all four TGCS groups.

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.

Digital Examination vs. 4D Transperineal Ultrasound-Do They Compare in Labour Management? A Pilot Study

The aim was to compare transperineal ultrasound (TPU) with parameters of the Bishop Score during the first stage of labour and evaluate how TPU can contribute towards improving labour management. Digital examination (DE) and TPU were performed on 42 women presenting at the labour ward with regular contractions. TPU measurements included the head-symphysis distance, angle of progression, diameter of the cervical wall, cervical dilation (CD) and cervical length (CL). To examine if TPU can monitor labour progress, correlations of TPU parameters were calculated. Agreement of DE and TPU was examined for CL and CD measurements and for two groups divided into latent (CD < 5 cm) and active stages of labour (CD ≥ 5 cm). TPU parameters indicated a moderate negative correlation of CD and CL (Pearson: r = -0.667; Spearman = -0.611). The other parameters showed a weak to moderate correlation. DE and TPU measurements for CD showed better agreement during the latent stage than during the active stage. The results of the present study add to the growing evidence that TPU may contribute towards an improved labour management, suggesting a combined approach of TPU and DE to monitor the latent first stage of labour and using only DE during the active stage of labour.

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.

New insights on labor progression: a systematic review

The past 20 years witnessed an invigoration of research on labor progression and a change of thinking regarding normal labor. New evidence is emerging, and more advanced statistical methods are applied to labor progression analyses. Given the wide variations in the onset of active labor and the pattern of labor progression, there is an emerging consensus that the definition of abnormal labor may not be related to an idealized or average labor curve. Alternative approaches to guide labor management have been proposed; for example, using an upper limit of a distribution of labor duration to define abnormally slow labor. Nonetheless, the methods of labor assessment are still primitive and subject to error; more objective measures and more advanced instruments are needed to identify the onset of active labor, monitor labor progression, and define when labor duration is associated with maternal/child risk. Cervical dilation alone may be insufficient to define active labor, and incorporating more physical and biochemical measures may improve accuracy of diagnosing active labor onset and progression. Because the association between duration of labor and perinatal outcomes is rather complex and influenced by various underlying and iatrogenic conditions, future research must carefully explore how to integrate statistical cut-points with clinical outcomes to reach a practical definition of labor abnormalities. Finally, research regarding the complex labor process may benefit from new approaches, such as machine learning technologies and artificial intelligence to improve the predictability of successful vaginal delivery with normal perinatal outcomes.

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.

Nomogram based on the final antepartum ultrasound features before delivery for predicting failed spontaneous vaginal delivery in nulliparous women

Background

Accurate identification of nulliparous women with failed spontaneous vaginal delivery (SVD) is crucial to minimize the hazards associated with obstetrical intervention (OI). While abnormal labor progression can be identified with intrapartum ultrasonography, labor-related complications may be unavoidable due to the limited time window left to the obstetrician. Antepartum ultrasound enables sufficient obstetric planning. However, there is typically a longer gap between ultrasound assessment and delivery that often lowers the prediction accuracy compared to intrapartum ultrasonography.

Objective

In this study, antepartum ultrasound assessment was included to each fetal ultrasound examination after 36 weeks of gestation until the onset of labor. We aim to establish a nomogram to predict the likelihood of failed SVD in nulliparous women using the last antepartum ultrasound findings before labor beginning.

Methods

Of the 2,143 nulliparous women recruited, 1,373 were included in a training cohort and 770 in a validation cohort, based on their delivery date. Maternal and perinatal characteristics, as well as perinatal ultrasound parameters were collected. In the training cohort, the screened correlates of SVD failure were used to develop a nomogram for determining whether a nulliparous woman would experience SVD failure. This model was validated in both training and validation cohorts.

Results

SVD failure affected 217 nulliparous women (10.13%). In the training cohort, SVD failure was independently associated with BMI [odds ratio (OR) = 1.636], FHC (OR = 1.194), CL (OR = 1.398), and PCA (OR = 0.824) (all P < 0.05). They constituted a nomogram to estimate the individual risk of SVD failure. The model obtained clinical net benefits in both the training and validation cohorts and was validated to present strong discrimination and calibration.

Conclusion

The developed nomogram based on the last antepartum ultrasound findings may be helpful in avoiding OI and its related complications by assessing the likelihood of a failed SVD in nulliparous women.

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.

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.

Incremental risk of clinical chorioamnionitis associated with cervical examination

BACKGROUND

Clinical chorioamnionitis is associated with significant maternal and neonatal morbidity, yet there is no clear evidence on the association between cervical examinations and infection.

OBJECTIVE

We sought to assess the association between the number of cervical examinations performed during term labor management and the risk of clinical chorioamnionitis.

STUDY DESIGN

This is a retrospective cohort study of term (≥37 weeks of gestation), singleton pregnancies who labored at our tertiary care center from 2014 to 2018. The primary outcome of clinical chorioamnionitis was defined as maternal intrapartum fever (single oral temperature of >39°C or 38°C-38.9°C for 30 minutes) and 1 or more of the following: maternal leukocytosis, purulent cervical drainage, or fetal tachycardia. The primary exposure was the number of digital cervical exams documented in the medical record. Log-binomial regression was used to model the effect of cervical examinations on the risk of clinical chorioamnionitis while adjusting for potential confounders.

RESULTS

A total of 20,029 individuals met the inclusion criteria and 1028 (5%) patients experienced clinical chorioamnionitis. The number of cervical exams was associated with increased risk of developing infection after adjusting for potential confounders. Individuals with ≥8 cervical exams had 1.7 times the risk of developing clinical chorioamnionitis compared with those with 1 to 3 exams. Prolonged rupture time, nulliparity, Black race, Medicaid insurance, higher gestational age, and higher body mass index were associated with increased risk of clinical chorioamnionitis, whereas smoking and group B Streptococcus colonization were associated with a lower risk.

CONCLUSION

Our study found that the number of cervical exams performed during labor is an independent risk factor for developing clinical chorioamnionitis. Unnecessary cervical exams should be avoided during labor management at term.

Applications of Advanced Ultrasound Technology in Obstetrics

Over the years, there have been several improvements in ultrasound technologies including high-resolution ultrasonography, linear transducer, radiant flow, three-/four-dimensional (3D/4D) ultrasound, speckle tracking of the fetal heart, and artificial intelligence. The aims of this review are to evaluate the use of these advanced technologies in obstetrics in the midst of new guidelines on and new techniques of obstetric ultrasonography. In particular, whether these technologies can improve the diagnostic capability, functional analysis, workflow, and ergonomics of obstetric ultrasound examinations will be discussed.