Refining the clinical definition of active phase arrest of dilation in nulliparous women to consider degree of cervical dilation as well as duration of arrest

Inconsistent definitions of prolonged labor in international literature: a scoping review

Objective

Prolonged labor is the commonest indication for intrapartum cesarean section, but definitions are inconsistent and some common definitions were recently found to overestimate the speed of physiological labor. The objective of this review is to establish an overview of synonyms and definitions used in the literature for prolonged labor, separated into first and second stages, and establish types of definitions used.

Data sources

A systematic search was conducted in PubMed, Embase, Web of Science, Cochrane Library, Emcare, and Academic Search Premier.

Study eligibility criteria

All articles in English that (1) attempted to define prolonged labor, (2) included a definition of prolonged labor, or (3) included any synonym for prolonged labor, were included.

Methods

Data on study design, year of publication, country or region of origin, synonyms used, definition of prolonged first and/or second stage, and origin of provided definition (if not primarily established by the study) were collected into a database.

Results

In total, 3402 abstracts and 536 full-text papers were screened, and 232 papers were included. Our search established 53 synonyms for prolonged labor. Forty-three studies defined prolonged labor and 189 studies adopted a definition of prolonged labor. Definitions for prolonged first stage of labor were categorized into: time-based (n=14), progress-based (n=12), clinician-based (n=5), or outcome-based (n=4). For the 33 studies defining prolonged second stage, the majority of definitions (n=25) were time-based, either based on total duration or duration of no descent of the presenting part.

Conclusions

Despite efforts to arrive at uniform labor curves, there is still little uniformity in definitions of prolonged labor. Consensus on which definition to use is called for, in order to safely and respectfully allow physiological labor progress, ensure timely management, and assess and compare incidence of prolonged labor between settings.

Changes of serum cortisol during pregnancy and labor initiation: an onsite cross-sectional study

Background

Increased maternal cortisol secretion has been observed during pregnancy and labor. However, due to the limitations in diagnostic methods, the dynamic change of cortisol during the short period between threatened labor and labor is unknown. In this study, we aim to evaluate the changes in serum cortisol during late pregnancy and full-term labor initiation, verifying if cortisol could serve as a biomarker for the diagnosis of labor initiation from threatened labor.

Methods

This cross-sectional onsite study involved 564 participants of 6 different gestational stages (C: Control; T1: Trimester 1; T3: Trimester 3; E: expectant; TL: threatened labor; L: labor), all patients in the E, TL, and L groups were at full term. The serum cortisol concentration was quantified with a point-of-care test (POCT), and the gestation, age, parity, and BMI of participants were documented. Morning serum cortisol was collected between 8:00 and 10:00 a.m., except for the TL and L group women who were tested upon arrival or during latent labor. With cortisol levels or all five variables, L was distinguished from TL using machine learning algorithms.

Results

Significant elevation of cortisol concentration was observed between T1 and T3, or TL and L group (P< 0.001). Women belonging to the E and TL group showed similar gestation week and cortisol levels. Diagnosis of labor initiation using cortisol levels (cutoff = 21.46 μg/dL) yielded sensitivity, specificity, and AUC of 86.50%, 88.60%, and 0.934. With additional variables, a higher specificity (89.29%) was achieved. The diagnostic accuracy of all methods ranged from 85.93% to 87.90%.

Conclusion

Serum cortisol could serve as a potential biomarker for diagnosis of L form TL. The rapid onsite detection of serum cortisol with POCT could facilitate medical decision-making for admission and special treatments, either as an additional parameter or when other technical platforms are not available.

Effect of Calcium Channel Blocker on Labor Curve in Pregnant Individuals with Chronic Hypertension

OBJECTIVE

This study aimed to compare the labor progress between individuals who received calcium channel blocker (CCB) and those who did not receive CCB during labor.

STUDY DESIGN

This was a secondary analysis of a retrospective cohort study of individuals with chronic hypertension who underwent vaginal delivery at a tertiary care center from January 2010 to December 2020. We excluded individuals with prior uterine surgeries and a 5-minute Apgar score of less than 5. We used a repeated-measures regression with a third-order polynomial function to compare the average labor curves according to antihypertensive medication. Estimates of the median (5th-95th percentile) traverse times between two dilations were computed using interval-censored regression.

RESULTS

Of 285 individuals with chronic hypertension, 88 (30.9%) received CCB. Individuals who received CCB during labor compared with those who did not were more likely to deliver at earlier gestational age and to have pregestational diabetes and superimposed preeclampsia (p  < 0.01). The progress of labor in the latent phase was not found to be significantly different between both groups (median: 11.51 vs. 8.74 hours; p = 0.08). However, after stratification by parity, nulliparous individuals who received CCB during labor were more likely to have a longer latent phase of labor (median: 14.4 vs. 8.5 hours; p  = 0.03) CONCLUSION:  A calcium channel blocker may slow the latent phase of labor in individuals with chronic hypertension. Aiming to minimize intrapartum iatrogenic interventions, allowing adequate time for pregnant individuals during the latent phase of labor is especially important if individuals are on a calcium channel blocker.

KEY POINTS

· Calcium channel blockers seem to be associated with a longer latent phase of labor.. · The effect of calcium channel blocker on labor was not observed in multiparous individuals.. · Allowing adequate labor time for individuals taking calcium channel blocker is important..

Duration of the active first stage of labour and severe perineal lacerations and maternal postpartum complications: a population-based cohort study

OBJECTIVE

The impact of first stage labour duration on maternal outcomes is sparsely investigated. We aimed to study the association between a longer active first stage and maternal complications in the early postpartum period.

DESIGN

A population-based cohort study.

SETTING

Regions of Stockholm and Gotland, Sweden, 2008-2020.

POPULATION

A cohort of 159 459 term, singleton, vertex pregnancies, stratified by parity groups.

METHODS

The exposure was active first stage duration, categorised in percentiles. Poisson regression analysis was performed to estimate the adjusted relative risk (aRR) and the 95% confidence interval (95% CI). To investigate the effect of second stage duration on the outcome, mediation analysis was performed.

MAIN OUTCOME MEASURES

Severe perineal lacerations (third or fourth degree), postpartum infection, urinary retention and haematoma in the birth canal or ruptured sutures.

RESULTS

The risks of severe perineal laceration, postpartum infection and urinary retention increased with a longer active first stage, both overall and stratified by parity group. The aRR increased with a longer active first stage, using duration of <50th percentile as the reference. In the ≥90th percentile category, the aRR for postpartum infection was 1.64 (95% CI 1.46-1.84) in primiparous women, 2.43 (95% CI 1.98-2.98) in parous women with no previous caesarean delivery (CD) and 2.33 (95% CI 1.65-3.28) in parous women with a previous CD. The proportion mediated by second stage duration was 33.4% to 36.9% for the different outcomes in primiparous women. The risk of haematoma or ruptured sutures did not increased with a longer active first stage.

CONCLUSIONS

Increasing active first stage duration is associated with maternal complications in the early postpartum period.

First stage of labour duration and associated risk of adverse neonatal outcomes

Prior evidence evaluating the benefits and harms of expectant labour duration during active first stage is inconclusive regarding potential consequences for the neonate. Population-based cohort study in Stockholm-Gotland region, Sweden, including 46,040 women (Robson 1), between October 1st, 2008 and June 15th, 2020. Modified Poisson regression was used for the association between active first stage of labour duration and adverse neonatal outcomes. 94.2% experienced a delivery with normal neonatal outcomes. Absolute risk for severe outcomes increased from 1.9 to 3.0%, moderate outcomes increased from 2.8 to 6.2% (> 10.1 h). Compared to the reference, (< 5.1 h; median), the adjusted relative risk (aRR) of severe neonatal outcome significantly increased beyond 10.1 h (> 90th percentile) (aRR 1.53, 95% CI 1.26, 1.87), for moderate neonatal outcome the aRR began to slowly increase beyond 5.1 h (≥ 50 percentile; aRR 1.40, 95% CI 1.24, 1.58). Mediation analysis indicate that most of the association was due to a longer active first stage of labour, 13% (severe neonatal outcomes) and 20% (moderate neonatal outcomes) of the risk was mediated (indirect effect) by longer second stage of labour duration. We report an association between increasing active first stage duration and increased risk of adverse neonatal outcomes. We did not observe a clear labour duration risk threshold.

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 evolution of the labor curve and its implications for clinical practice: the relationship between cervical dilation, station, and time during labor

The assessment of labor progress is germane to every woman in labor. Two labor disorders-arrest of dilation and arrest of descent-are the primary indications for surgery in close to 50% of all intrapartum cesarean deliveries and are often contributing indications for cesarean deliveries for fetal heart rate abnormalities. Beginning in 1954, the assessment of labor progress was transformed by Friedman. He published a series of seminal works describing the relationship between cervical dilation, station of the presenting part, and time. He proposed nomenclature for the classification of labor disorders. Generations of obstetricians used this terminology and normal labor curves to determine expected rates of dilation and fetal descent and to decide when intervention was required. The analysis of labor progress presents many mathematical challenges. Clinical measurements of dilation and station are imprecise and prone to variation, especially for inexperienced observers. Many interrelated factors influence how the cervix dilates and how the fetus descends. There is substantial variability in when data collection begins and in the frequency of examinations. Statistical methods to account for these issues have advanced considerably in recent decades. In parallel, there is growing recognition among clinicians of the limitations of using time alone to assess progress in cervical dilation in labor. There is wide variation in the patterns of dilation over time and most labors do not follow an average dilation curve. Reliable assessment of labor progression is important because uncertainty leads to both over-use and under-use of cesarean delivery and neither of these extremes are desirable. This review traces the evolution of labor curves, describes how limitations are being addressed to reduce uncertainty and to improve the assessment of labor progression using modern statistical techniques and multi-dimensional data, and discusses the implications for obstetrical practice.

Assessment of labor progress by ultrasound vs manual examination: a randomized controlled trial

BACKGROUND

Assessment of labor progress via digital examination is considered the standard of care in most delivery rooms. However, this method can be stressful, painful, and imprecise, and multiple examinations increase the risk for chorioamnionitis. Intrapartum ultrasound was found to be an objective, noninvasive tool to monitor labor progression.

OBJECTIVE

This study aimed to investigate whether, among nulliparous women, the use of intrapartum ultrasound can reduce the rate of intrapartum fever by reducing the number of digital examinations.

STUDY DESIGN

This was a prospective, randomized controlled trial in term nulliparas admitted with prelabor rupture of membranes, induction of labor, or in latent phase of labor with a cervical dilation of <4 cm. Women were randomized into 1 of the following 2 arms: (1) labor progress assessed by ultrasound, avoiding digital examinations as much as possible; and (2) control group in which labor progression was assessed according to the regular protocol. Before the study, all labor ward physicians underwent training in intrapartum ultrasound.

RESULTS

A total of 90 women were randomized to the ultrasound group and 92 were randomized to the control group. When compared with the control group, the ultrasound group had significantly lower rates of intrapartum fever (11.1% vs 26.1%; P=.01), clinical chorioamnionitis (3.3% vs 16.5%; P>.01), and histologic chorioamnionitis (2.2% vs 9.8%; P=.03). The median number of digital examinations was significantly lower in the ultrasound group (5; interquartile range, 4-6) than in the control group (8; interquartile range, 6-10; P<.01). The median number of digital examinations per hour in the ultrasound group was significantly lower than in the control group (0.2 vs 0.4; P<.01). The induction rates, time from admission to delivery, mode of delivery, Apgar score at 5 minutes, and neonatal intensive care unit admission rates did not differ significantly between the groups.

CONCLUSION

The use of intrapartum ultrasound lessens the total number of digital examinations needed to be performed during labor and, consequently, the incidence of intrapartum fever and chorioamnionitis are reduced. No adverse effects on labor progression and short-term maternal or neonatal outcomes were noted.

The sonographic measurement of the ratio between the fetal head circumference and the obstetrical conjugate is accurate in predicting the risk of labor arrest: results from a multicenter prospective study

BACKGROUND

Labor arrest is estimated to account for approximately one-third of all primary cesarean deliveries, and is associated with an increased risk of adverse maternal and perinatal outcomes. One of the main causes is the mismatch between the size of the birth canal and that of the fetus, a condition usually referred to as cephalopelvic disproportion.

OBJECTIVE

This study aimed to describe a new ultrasound predictor of labor arrest leading to cesarean delivery because of suspected cephalopelvic disproportion.

STUDY DESIGN

This was a multicenter prospective study conducted at 3 maternity units from January 2021 to January 2022. A nonconsecutive series of singleton pregnancies with cephalic-presenting fetuses, gestational age of 34 weeks+0 days or above, and no contraindication to vaginal delivery attending at the antenatal clinics of each institution were considered eligible. Between 34+0 and 38+0 weeks of gestation, all eligible patients were submitted to transabdominal 2D ultrasound measurement of the obstetrical conjugate. On admission to the labor ward, the fetal head circumference was measured on the standard transthalamic plane by transabdominal ultrasound. The primary outcome of the study was the accuracy of the ratio between the fetal head circumference and the obstetrical conjugate measurement (ie, head circumference/obstetrical conjugate ratio) in predicting the occurrence of cesarean delivery secondary to labor arrest. The secondary outcome was the relationship between the head circumference/obstetrical conjugate ratio and labor duration.

RESULTS

A total of 263 women were included. Cesarean delivery for labor arrest was performed in 7.6% (20/263) of the included cases and was associated with more frequent use of epidural analgesia (95.0% vs 45.7%; P<.001), longer second stage of labor (193 [120-240] vs 34.0 [13.8-66.5] minutes; P=.002), shorter obstetrical conjugate (111 [108-114] vs 121 [116-125] mm; P<.001), higher head circumference/obstetrical conjugate ratio (3.2 [3.2-3.35] vs 2.9 [2.8-3.0]; P<.001), and higher birthweight (3678 [3501-3916] vs 3352 [3095-3680] g; P=.003) compared with vaginal delivery. At logistic regression analysis, the head circumference/obstetrical conjugate ratio expressed as Z-score was the only parameter independently associated with risk of cesarean delivery for labor arrest (odds ratio, 8.8; 95% confidence interval, 3.6-21.7) and had higher accuracy in predicting cesarean delivery compared with the accuracy of fetal head circumference and obstetrical conjugate alone, with an area under the curve of 0.91 (95% confidence interval, 81.7-99.5; P<.001). A positive correlation between the head circumference/obstetrical conjugate ratio and length of the second stage of labor was found (Pearson coefficient, 0.16; P=.018).

CONCLUSION

Our study, conducted on an unselected low-risk population, demonstrated that the head circumference/obstetrical conjugate ratio is a reliable antenatal predictor of labor arrest leading to cesarean delivery.