Labor Dystocia: A Common Approach to Diagnosis

Physiological plateaus during normal labor and birth: A novel definition

BACKGROUND

Diagnoses of labor dystocia, and subsequent labor augmentation, make one of the biggest contributions to childbirth medicalization, which remains a key challenge in contemporary maternity care. However, labor dystocia is poorly defined, and the antithetical concept of physiological plateaus remains insufficiently explored.

AIM

To generate a definition of physiological plateaus as a basis for further research.

METHODS

This qualitative study applied grounded theory methods and comprised interviews with 20 midwives across Australia, conducted between September 2020 and February 2022. Data were coded in a three-phase approach, starting with inductive line-by-line coding, which generated themes and subthemes, and finally, through axial coding.

RESULTS

Physiological plateaus represent a temporary slowing of one or multiple labor processes and appear to be common during childbirth. They are reported throughout the entire continuum of labor, typically lasting between a few minutes to several hours. Their etiology/function appears to be a self-regulatory mechanism of the mother-infant dyad. Physiological plateaus typically self-resolve and are followed by a self-resumption of labor. Women with physiological plateaus during labor appear to experience positive birth outcomes.

DISCUSSION

Despite appearing to be common, physiological plateaus are insufficiently recognized in contemporary childbirth discourse. Consequently, there seems to be a significant risk of misinterpretation of physiological plateaus as labor dystocia. While findings are limited by the qualitative design and require validation through further quantitative research, the proposed novel definition provides an important starting point for further investigation.

CONCLUSION

A better understanding of physiological plateaus holds the potential for a de-medicalization of childbirth through preventing unjustified labor augmentation.

Neonatal head circumference to maternal mid-transverse pelvic distance ratio as a key anatomical predictor for dystocia: Retrospective case-control study

OBJECTIVE

This study aimed to examine maternal and neonatal factors in cesarean deliveries due to dystocia, including cephalopelvic disproportion, latent-phase prolongation, and fetal malposition or malpresentation. Additionally, we sought to compare the differences between the dystocia subgroups.

METHOD AND MATERIALS

This retrospective case-control study included women who delivered between January 2010 and June 2021 after 37 weeks of pregnancy and underwent abdominal-pelvic CT scans within 5 years before and after delivery. Neonatal factors were extracted from medical charts immediately after delivery.

RESULTS

Among the 292 women studied, those with cesarean deliveries for dystocia were older (mean ± SD, 34.2 ± 4.27 vs. 32.2 ± 3.8, p-value = 0.002), had higher pre-pregnancy BMI (22.7 ± 3.67 vs. 21.4 ± 3.48, p-value = 0.012) and term-BMI (27.4 ± 3.72 vs. 25.9 ± 3.66, p-value = 0.010), shorter interspinous distance (ISD, the distance between ischial spine) (10.8 ± 0.76 vs. 11.2 ± 0.85 cm, p-value = 0.003), and longer head circumference (HC) (35 ± 1.47 vs. 34.4 ± 1.36 cm, p-value = 0.003) compared to those who had vaginal deliveries. Univariate logistic regression for dystocia revealed associations between HC/maternal height and HC/ISD ratios (OR, 2.02 [95% confidence interval, CI, 1.4 ~ 2.92], 12.13 [3.2 ~ 46.04], respectively). Multivariate logistic analysis indicated that maternal age, ISD, and HC were significant factors for dystocia (OR, 1.11 [95% CI, 1.01 ~ 1.21], 0.49 [0.26 ~ 0.91], 1.53 [1.07 ~ 2.19], respectively). The subgroup with latent-phase prolongation exhibited the lowest birthweight/term-BMI ratio (124 ± 18.8 vs. 113 ± 10.3 vs. 134 ± 19.1, p-value = 0.013).

CONCLUSION

The HC/ISD ratio emerged as a crucial predictor of dystocia, suggesting that reducing term-BMI could potentially mitigate latent-phase prolongation. Further research assessing the maternal mid-pelvis during pregnancy and labor is warranted, along with efforts to reduce BMI during pregnancy.

Characterizing uterine responsiveness to oxytocin augmentation across four labor patterns in maternal obesity

BACKGROUND

Optimizing care during labor protraction is a key strategy for reducing cesareans, especially among people with obesity. The pathophysiology of labor dystocia remains poorly understood, limiting precise interventions targeting the cause of protraction.

METHODS

In this secondary analysis of nulliparas (n = 92) with obesity (BMI ≥ 30 kg/m2) and spontaneous labor onset, we classified labor into four phenotypes based on duration of protraction and birth route: (1) no protraction, (2) short protraction and vaginal birth, (3) extended protraction meeting criteria for labor arrest, but with eventual progression and vaginal birth, and (4) extended protraction meeting criteria for labor arrest and cesarean birth. Across these phenotypes, we compared MVU, oxytocin dose, and novel measures of uterine responsiveness to oxytocin augmentation (MVU to oxytocin dose ratios).

RESULTS

In our sample, phenotype group 1 comprised 14.1% (n = 13); group 2 comprised 30.4% (n = 28); group 3 comprised 34.8% (n = 32); and group 4 comprised 20.7% (n = 19). Uterine responsiveness to oxytocin, but not MVU, decreased with each labor phenotype. Participants with cesarean birth had the lowest uterine responsiveness to oxytocin.

CONCLUSION

Labor and birth outcomes were associated with measures of uterine responsiveness to oxytocin rather than MVU alone, and thus these may be more clinically appropriate measures for guiding clinical decision-making. Current criteria for labor arrest are likely too stringent for nulliparas with obesity, many of whom appear to progress to safe vaginal birth after longer labor durations. Differences in uterine responsiveness to oxytocin augmentation across the groups suggests underlying physiologic differences in the labor phenotypes, which should drive future research targeting pathophysiology.

The Relationship Between Uterine Activity, Oxytocin Dosing, Labor Progress, and Mode of Birth in Nulliparas with Obesity: Minimal Usefulness of Montevideo Unit Measurement

BACKGROUND

Maternal obesity and cesarean birth disproportionately affect Black parturients; thus, prevention of cesarean birth is a key modifiable factor to improve pregnancy outcomes and reduce disparities. The primary driver of unplanned cesarean birth among people with higher body mass index is prolonged labor duration. However, strategies to optimize outcomes in these situations have not been established. We aimed to evaluate the influence of oxytocin augmentation on uterine activity and labor progression in nulliparas with obesity.

METHODS

This secondary analysis involved nulliparas with obesity (BMI ≥30 kg/m2) who had spontaneous labor onset followed by oxytocin augmentation and an intrauterine pressure catheter. Using Linear Mixed Models, we evaluated relationships between uterine activity measured in Montevideo units (MVU), oxytocin dose, and rate of cervical dilation normalized by labor duration.

RESULTS

In this diverse sample (35.6% Caucasian, 16.11% African American, 40.2% Hispanic) of nulliparas with obesity (n = 87; BMI 35.54 ± 4.38 kg/m2), 31% ended labor with cesarean birth. Among those with vaginal birth, only 13% had MVU ≥200 prior to the final 2 hours of labor. MVUs were only minimally responsive to oxytocin dose and were not associated with labor progression nor birth route.

CONCLUSION

MVU measurements may not be useful to diagnose labor arrest in nulliparas with obesity. Optimizing care for birthing people with obesity is essential for improving perinatal outcomes and for reducing racial health disparities.

The Pathophysiology of Labor Dystocia: Theme with Variations

Abnormally prolonged labor, or labor dystocia, is a common complication of parturition. It is the indication for about half of unplanned cesarean deliveries in low-risk nulliparous women. Reducing the rate of unplanned cesarean birth in the USA has been a public health priority over the last two decades with limited success. Labor dystocia is a complex disorder due to multiple causes with a common clinical outcome of slow cervical dilation and fetal descent. A better understanding of the pathophysiologic mechanisms of labor dystocia could lead to new clinical opportunities to increase the rate of normal vaginal delivery, reduce cesarean birth rates, and improve maternal and neonatal health. We conducted a literature review of the causes and pathophysiologic mechanisms of labor dystocia. We summarize known mechanisms supported by clinical and experimental data and newer hypotheses with less supporting evidence. We review recent data on uterine preparation for labor, uterine contractility, cervical preparation for labor, maternal obesity, cephalopelvic disproportion, fetal malposition, intrauterine infection, and maternal stress. We also describe current clinical approaches to preventing and managing labor dystocia. The variation in pathophysiologic causes of labor dystocia probably limits the utility of current general treatment options. However, treatments targeting specific underlying etiologies could be more effective. We found that the pathophysiologic basis of labor dystocia is under-researched, offering wide opportunities for translational investigation of individualized labor management, particularly regarding uterine metabolism and fetal position. More precise diagnostic tools and individualized therapies for labor dystocia might lead to better outcomes. We conclude that additional knowledge of parturition physiology coupled with rigorous clinical evaluation of novel biologically directed treatments could improve obstetric quality of care.

Women’s views and experiences of augmentation of labour with synthetic oxytocin infusion. A protocol for a qualitative evidence synthesis

Background: Augmentation of labour (AOL) is the most common intervention to treat labour dystocia. Previous research reported extensive disparities in AOL rates across countries and institutions.  Despite its widespread use, women’s views on and experiences of intrapartum augmentation with infused synthetic oxytocin are limited.

Methods: A qualitative evidence synthesis on women’s views and experiences of AOL with synthetic oxytocin after spontaneous onset of labour will be conducted. Qualitative studies and studies employing a mixed methods design, where qualitative data can be extracted separately, will be included, as will surveys with open-ended questions that provide qualitative data. A systematic search will be performed of the databases: MEDLINE, CINAHL, EMBASE, PsycINFO, Maternity and Infant Care and Web of Science Core Collection from the date of inception. The methodological quality of included studies will be assessed using the Evidence for Policy and Practice Information and Co-ordinating Centre’s appraisal tool. A three-stage approach, coding of data from primary studies, development of descriptive themes and generation of analytical themes, will be used to synthesise findings. Confidence in findings will be established by the Grading of Recommendations Assessment, Development and Evaluation-Confidence in the Evidence from Reviews of Qualitative research.

Discussion: This qualitative evidence synthesis may provide valuable information on women’s experiences of AOL and contribute to a review of clinical practice guidelines for maternity care providers.

PROSPERO registration: CRD42021285252 (14/11/2021)

Women’s views and experiences of augmentation of labour with synthetic oxytocin infusion: a protocol for a qualitative evidence synthesis

Background: Augmentation of labour (AOL) is the most common intervention to treat labour dystocia. Previous research reported extensive disparities in AOL rates across countries and institutions.  Despite its widespread use, women’s views on and experiences of intrapartum augmentation with infused synthetic oxytocin are limited. Methods: A qualitative evidence synthesis on women’s views and experiences of AOL with synthetic oxytocin after spontaneous onset of labour will be conducted. Qualitative studies and studies employing a mixed methods design, where qualitative data can be extracted separately, will be included, as will surveys with open-ended questions that provide qualitative data. A systematic search will be performed of the databases: MEDLINE, CINAHL, EMBASE, PsycINFO, Maternity and Infant Care and Web of Science Core Collection from the date of inception. The methodological quality of included studies will be assessed using the Evidence for Policy and Practice Information and Co-ordinating Centre’s appraisal tool. A three-stage approach, coding of data from primary studies, development of descriptive themes and generation of analytical themes, will be used to synthesise findings. Confidence in findings will be established by the Grading of Recommendations Assessment, Development and Evaluation-Confidence in the Evidence from Reviews of Qualitative research. Discussion: This qualitative evidence synthesis may provide valuable information on women’s experiences of AOL and contribute to a review of clinical practice guidelines for maternity care providers. PROSPERO registration: CRD42021285252 (14/11/2021)

The Labour Progression Study (LaPS): Duration of labour following Zhang's guideline and the WHO partograph - A cluster randomised trial

OBJECTIVE

To investigate labour duration in different phases of labour when adhering to Zhang's guideline for labour progression compared with the WHO partograph.

DESIGN

A secondary analysis of a cluster randomised controlled trial.

SETTING

Fourteen Norwegian birth care units, each with more than 500 deliveries per year constituted the clusters.

PARTICIPANTS

A total of 7277 nulliparous women with singleton foetus in a cephalic presentation and spontaneous onset of labour at term were included.

INTERVENTION

Seven clusters were randomised to the intervention group that adhered to Zhang's guideline (n = 3972) and seven to the control group that adhered to the WHO partograph (n = 3305) for labour progression.

MEASUREMENTS

The duration of labour from the first registration of cervical dilatation (≥ 4 cm) to the delivery of the baby and the duration of the first and second stages of labour; the time-to-event analysis was used to compare the duration of labour between the two groups after adjusting for baseline covariates.

FINDINGS

The adjusted median duration of labour was 7.0 h in the Zhang group, compared with 6.2 h in the WHO group; the median difference was 0.84 h with 95% confidence interval [CI] (0.2-1.5). The adjusted median duration of the first stage was 5.6 h in the Zhang group compared with 4.9 h in the WHO group; the median difference was 0.66 h with 95% CI (0.1-1.2). The corresponding adjusted median duration of the second stage was 88 and 77 min; the median difference was 0.18 h with 95% CI (0.1-0.3).

KEY CONCLUSIONS

The women who adhered to Zhang's guideline had longer overall duration and duration of the first and second stages of labour than women who adhered to the WHO partograph.

IMPLICATIONS FOR PRACTICE

Understanding the variations in the duration of labour is of great importance, and the results offer useful insights into the different labour progression guidelines, which can inform clinical practice.

The ARRIVE Trial: Interpretation from an Epidemiologic Perspective

The findings of the ARRIVE trial (A Randomized Trial of Induction Versus Expectant Management) were recently published. This multisite randomized trial was designed to provide evidence regarding whether labor induction or expectant management is associated with increased adverse perinatal outcomes and risk of cesarean birth among healthy nulliparous women at term. The trial reported that the primary outcome, a composite of adverse neonatal outcomes, was not significantly different between the 2 groups; the principal secondary outcome, cesarean birth, was significantly more common among women whose pregnancy was expectantly managed than among women whose labor was induced at 39 weeks. These results have the potential to change existing practice. Several aspects of the study design may influence its potential internal and external validity and should be considered in order to make sound causal inferences from this trial, which will in turn affect how its findings are translated to practice. Although chance and confounding are of minimal concern, given the sample size and randomization used in the study, selection bias may be a concern. Studies are vulnerable to selection bias when the sample population differs from eligible nonparticipants, including in randomized controlled trials. External validity is defined as the extent to which the study population and setting are representative of the larger source population the study intends to represent. External validity may be limited given the characteristics of the women enrolled in the ARRIVE trial and the practice settings where the study was conducted. This brief report provides concrete suggestions for further analyses that could help solidify conclusions from the trial, and for further research questions that will continue advancement toward answering this complex question of how best to manage labor and birth decisions at full term among low-risk women.

Applying a physiologic partograph to Consortium on Safe Labor data to identify opportunities for safely decreasing cesarean births among nulliparous women

BACKGROUND

The timing of hospital admission for women with spontaneous labor onset and the criteria used to assess active labor progress and diagnose labor dystocia may significantly influence women's risk for primary cesarean birth. Our aims were to assess associations of labor status at admission (i.e., preactive or active) and active labor progress (i.e., dystocic or physiologic) with oxytocin augmentation, cesarean birth, and adverse neonatal outcome rates.

METHODS

A sample of low-risk, nulliparous women admitted to hospitals for spontaneous labor onset was extracted from the Consortium on Safe Labor (n = 27 077). Binomial logistic regression was used to assess associations between labor classifications and outcomes.

RESULTS

At admission, 68.0% of women were in preactive labor and 32.0% were in active labor. Cesarean rates for these groups were 18.0% and 7.2%, respectively (adjusted odds ratio [AOR] 2.69; 95% CI 2.45-2.96). Oxytocin augmentation and adverse neonatal outcomes were more likely for women admitted in preactive labor. Among women admitted in active labor, 9.3% experienced labor dystocia and 90.7% progressed physiologically. Cesarean rates for these groups were 20.4% and 5.9%, respectively (AOR 3.02; 95% CI 2.45-3.73). Nearly half of the cesareans performed for dystocia among women admitted in active labor occurred when cervical dilation was physiologic. Oxytocin augmentation and adverse neonatal outcomes were more likely when active labor was dystocic.

CONCLUSIONS

Adoption of evidence-based, standardized approaches for diagnosing active labor onset, assessing labor progress, and diagnosing dystocia may safely decrease oxytocin augmentation and cesarean birth rates in the United States.

In silico analysis of the Mus musculus uterine gene expression landscape during pregnancy identifies putative upstream regulators for labour

BACKGROUND

The molecular pathways involved in the transition from uterine quiescence to overt labour are mapped and form the currently established pharmacological targets for both the induction and inhibition of human labour. However, both spontaneous premature labour and functional dystocia occur and are difficult to treat adequately. The identification of upstream regulators involved in the onset and orchestration of labour pathways is essential to develop additional therapies that will contribute to the regulation of the timing of birth.

OBJECTIVES

To define uterine biological processes and their upstream activators involved in the transition from uterine quiescence to overt labour.

STUDY DESIGN

The uterus of non-pregnant and pregnant FVB M. musculus is collected at embryonic days (E) 6.5, 8.5, 10.5, 12.5, 15.5 and 17.5 and the uterine transcriptome is determined using the Illumina mouse Ref8v2 micro-array platform. K-means clustering and Ingenuity Pathway Analysis are applied to further dissect the transcriptome data.

RESULTS

From E6.5 to E17.5, 5405 genes are significantly differentially expressed and they segregate into 7 unique clusters. Five of the 7 clusters are enriched for genes involved in specific biological processes that include regulation of gene-expression, T-cell receptor activation, Toll-like receptor signalling and steroid metabolism. The identification of upstream activators for differentially expressed genes between consecutive time points highlights the E10.5 to E12.5 window during which the role from progesterone switches from an activated state to the inhibited state reflecting the process of functional progesterone withdrawal essential for the transgression from myometrial quiescence to synchronized contractions. For this time window in which 189 genes are differentially expressed we define 22 putative upstream activators of which NUPR1 and TBX2 are the most significant with respectively an activated and an inhibited status.

CONCLUSIONS

Gene expression profiling of mice uterus from E6.5 to E17.5 results in 7 unique gene expression clusters from early to late pregnancy that define the landscape of molecular events in ongoing pregnancy. In the current dataset progesterone is predicted as an activated upstream regulator and maintainer of myometrial quiescence and is active till E10.5. Progesterone is predicted as an inhibited upstream regulator at E12.5. We identify 22 upstream regulators in the E10.5 to E12.5 time window where the switch to progesterone withdrawal occurs. They are putative relevant upstream activators of labour.

Impact factors on cervical dilation rates in the first stage of labor

AIMS

To assess cervical dilation rates of nulliparous and multiparous women in the active first stage of labor and to evaluate significant impact factors.

METHODS

In a retrospective cohort study between January 2007 and July 2014 at the University Hospital of Zurich in Switzerland, we analyzed 8378 women with singleton pregnancies in vertex presentation with a vaginal delivery at 34+0 to 42+5 gestational weeks. Median cervical dilation rates were calculated and different impact factors evaluated.

RESULTS

Cervical dilation rates increase during labor progress with faster rates in multiparous compared with nulliparous women (P<0.001). Dilation rates exceed 1 cm/h at a dilatation of 6-7 cm, but are very individual. Accelerating impact factors are multiparity, a greater amount of cervical dilation and fetal occipitoanterior position, whereas the use of epidural anesthesia, a higher fetal weight and head circumference decelerate dilation (P<0.001).

CONCLUSION

Cervical dilation is a hyperbolic increasing process, with faster dilation rates in multiparous compared to nulliparous women and a reversal point of labor around 6-7 cm, respectively. Besides, cervical dilation is highly individual and affected by several impact factors. The diagnosis of labor arrest or prolonged labor should therefore be based on such rates and on the individual evaluation of every woman.

Likelihood of cesarean delivery after applying leading active labor diagnostic guidelines

BACKGROUND

Friedman, the United Kingdom's National Institute for Health and Care Excellence (NICE), and the American College of Obstetricians and Gynecologists/Society for Maternal-Fetal Medicine (ACOG/SMFM) support different active labor diagnostic guidelines. Our aims were to compare likelihoods for cesarean delivery among women admitted before vs in active labor by diagnostic guideline (within-guideline comparisons) and between women admitted in active labor per one or more of the guidelines (between-guideline comparisons).

DESIGN

Active labor diagnostic guidelines were retrospectively applied to cervical examination data from nulliparous women with spontaneous labor onset (n = 2573). Generalized linear models were used to determine outcome likelihoods within- and between-guideline groups.

RESULTS

At admission, 15.7%, 48.3%, and 10.1% of nulliparous women were in active labor per Friedman, NICE, and ACOG/SMFM diagnostic guidelines, respectively. Cesarean delivery was more likely among women admitted before vs in active labor per the Friedman (AOR 1.75 [95% CI 1.08-2.82] or NICE guideline (AOR 2.55 [95% CI 1.84-3.53]). Between guidelines, cesarean delivery was less likely among women admitted in active labor per the NICE guideline, as compared with the ACOG/SMFM guideline (AOR 0.55 [95% CI 0.35-0.88]).

CONCLUSION

Many nulliparous women are admitted to the hospital before active labor onset. These women are significantly more likely to have a cesarean delivery. Diagnosing active labor before admission or before intervention to speed labor may be one component of a multi-faceted approach to decreasing the primary cesarean rate in the United States. The NICE diagnostic guideline is more inclusive than Friedman or ACOG/SMFM guidelines and its use may be the most clinically useful for safely lowering cesarean rates.