Physiology of pain in labour

Global research trends in labor analgesia: A bibliometric analysis from 2013 to 2023

Objective

In the past decade, thousands of original articles focus on labor analgesia have published. However, little has been published in the literature that includes a bibliometric analysis of labor analgesia. Therefore, this study is designed to analyze the current status of research on labor analgesia over the past ten years and explore potential directions for the future.

Methods

We retrieved the Web of Science Core Collection (WOSCC) for labor analgesia articles published from 2013 to 2023 and extracted the data from the literature. To perform the bibliometric analysis, we used CiteSpace (6.2. R5) and VOS viewer (1.6.19) as our primary analysis tools.

Results

A total of 2406 articles were included, and the number of publications has increased steadily in the last ten years. The United States was the leading contributor to the area, and Harvard University was the most productive institution. The American Journal of Obstetrics and Gynecology was the most cited and influential journal. The most co-cited reference was "Epidural versus non-epidural or no analgesia for pain management in labour". The labels of the co-citation cluster have identified the characteristics of 5major clusters, such as "postpartum depression", "programmed intermittent epidural bolus", "childbirth experience" "intrapartum maternal fever" and "dural puncture", which play important roles in this field. Keywords co-occurrence and keywords burst detection showed that "vaginal birth", "postpartum depression", "maternal fever", "inflammation", "systematic review", "guidelines", "decreased risk" and "scale" were the most recent and most prominent topics of labor analgesia.

Discussion

This study provided a global review of labor analgesia using bibliometric and visual techniques to provide an intuitive understanding of this topic and identify hotspots and research trends. Notably, intrapartum fever and postpartum depression have emerged as hotpots and trends in labor analgesia research, reflecting the current research landscape.

Risk factors for postpartum posttraumatic stress disorder after emergency admission

BACKGROUND

Postpartum posttraumatic stress disorder (PTSD) can occur in women who give birth after emergency admission. The identification of risk factors for this condition is crucial for developing effective preventive measures. This retrospective study aimed to explore the incidence and risk factors for postpartum PTSD in women who give birth after emergency admission.

METHODS

Medical records of women who gave birth after emergency admission were collected between March 2021 and April 2023. The patients' general conditions and perinatal clinical indicators were recorded. The puerperae were divided into PTSD group and control group based on symptom occurrence at six weeks postpartum. Multivariate logistic regression analysis was performed to identify risk factors.

RESULTS

A total of 276 puerperae were included, with a PTSD incidence of 20.3% at six weeks postpartum. Multivariate logistic regression analysis identified emergency cesarean section (odds ratio [OR]=2.102; 95% confidence interval [CI]: 1.114-3.966, P=0.022), admission to the emergency department after midnight (12:00 AM) (OR=2.245; 95%CI: 1.170-4.305, P<0.001), and cervical dilation (OR=3.203; 95%CI: 1.670-6.141, P=0.039) as independent risk factors for postpartum PTSD. Analgesia pump use (OR= 0.500; 95%CI: 0.259-0.966, P=0.015) was found to be a protective factor against postpartum PTSD.

CONCLUSION

Emergency cesarean section, admission to the emergency department after midnight, and cervical dilation were identified as independent risk factors for postpartum PTSD, while analgesic pump use was a protective factor. These findings provide insights for developing more effective preventive measures for women who give birth after emergency admission.

Beyond Fear: Unveiling the Relationship Between Fear of Childbirth and Pharmacological Pain Relief

BACKGROUND

Pharmacological analgesia is the dominant method for pain relief in labor. Fear of childbirth (FOC) may significantly affect women's preferences for and usage of pharmacological analgesia.

AIM

This study aimed to investigate the relationship between FOC in late pregnancy and preferences for, as well as actual use of, pharmacological analgesia among nulliparous and multiparous women, accounting for confounding factors.

METHODS

A total of 1,300 women participated in the study, completing questionnaires assessing preferences for pharmacological analgesia, FOC, perception of labor pain, social support, coping styles, and demographic variables. The actual use of pharmacological analgesia was followed up. The data were analyzed using univariate and multivariate regression analyses.

RESULTS

Univariate analysis revealed that women with moderate to severe FOC had a stronger preference for pharmacological analgesia compared to those with none to mild FOC. However, multivariate analysis showed no direct association between FOC and actual usage of pharmacological analgesia. Instead, a stronger preference for pharmacological analgesia increased the likelihood of its actual usage during labor.

CONCLUSIONS

Our study underscores the effect of FOC on preferences for pharmacological analgesia and its potential influence on actual usage during labor. Healthcare providers should consider women's FOC and preferences when evaluating pain management options. Targeted interventions focusing on promoting non-pharmacological techniques should be implemented to optimize labor pain management for women, particularly nulliparous women.

Tools for assessing labour pain: a comprehensive review of research literature

ABSTRACT

The experience of pain associated with labour is complex and challenging to assess. A range of pain measurement tools are reported in the literature. This review aimed to identify current tools used in research to assess labour pain across the past decade and to evaluate their implementation and adequacy when used in the context of labour pain. A literature search was conducted in databases MEDLINE and Cumulative Index of Nursing and Allied Health Literature, using search terms relating to labour, pain, and measurement. A total of 363 articles were selected for inclusion. Most studies (89.9%) assessed pain as a unidimensional experience, with the most common tool being the Visual Analogue Scale, followed by the Numerical Rating Scale. Where studies assessed pain as a multidimensional experience, the most common measurement tool was the McGill Pain Questionnaire. Only 4 studies that used multidimensional tools selected a tool that was capable of capturing positive affective states. Numerous variations in the implementation of scales were noted. This included 35 variations found in the wording of the upper and lower anchors of the Visual Analogue Scale, some assessment tools not allowing an option for "no pain," and instances where only sections of validated tools were used. It is clear that development of a standardised pain assessment strategy, which evaluates the multidimensions of labour pain efficiently and effectively and allows for both positive and negative experiences of pain to be reported, is needed.

Analgesia in Pregnancy

Pain management during labor and delivery is complex and must balance efficacy and toxicity to both the pregnant person and the fetus. There are numerous ways to achieve safe and effective analgesia and anesthesia during labor and delivery, including neuraxial and nonneuraxial techniques. This review describes important anesthetic considerations that should be made when formulating a pain management plan and an overview of common anesthesia-related complications encountered in the obstetric population.

Prolonged Dystocic Labor in Neuraxial Analgesia and the Role of Enkephalin Neurotransmitters: An Experimental Study

The investigation studied the enkephalinergic neuro fibers (En) contained in the Lower Uterine Segment (LUS) during the prolonged dystocic labor (PDL) with Labor Neuraxial Analgesia (LNA). PDL is generally caused by fetal head malpositions in the Occiput Posterior Position (OPP), Persistent Occiput Posterior Position (POPP), in a transverse position (OTP), and asynclitism (A), and it is detected by Intrapartum Ultrasonography (IU). The En were detected in the LUS samples picked up during cesarean section (CS) of 38 patients undergoing urgent CS in PDL, compared to 37 patients submitted to elective CS. Results were statistically evaluated to understand the differences in En morphological analysis by scanning electron microscopy (SEM) and by fluorescence microscopy (FM). The LUS samples analysis showed an important reduction in En in LUS of CS for the PDL group, in comparison with the elective CS group. The LUS overdistension, by fetal head malpositions (OPP, OTP, A) and malrotations, lead to dystocia, modification of vascularization, and En reduction. The En reduction in PDL suggests that drugs used during the LNA, usually local anesthetics and opioids, cannot control the "dystocic pain", that differs from normal labor pain. The IU administration in labor and the consequent diagnosis of dystocia suggest stopping the numerous and ineffective top-up drug administration during LNA, and to shift the labor to operative vaginal delivery or CS.

Parturition in Mammals: Animal Models, Pain and Distress

Parturition is a complex physiological process and involves many hormonal, morphological, physiological, and behavioural changes. Labour is a crucial moment for numerous species and is usually the most painful experience in females. Contrary to the extensive research in humans, there are limited pain studies associated with the birth process in domestic animals. Nonetheless, awareness of parturition has increased among the public, owners, and the scientific community during recent years. Dystocia is a significant factor that increases the level of parturition pain. It is considered less common in polytocous species because newborns' number and small size might lead to the belief that the parturition process is less painful than in monotocous animal species and humans. This review aims to provide elements of the current knowledge about human labour pain (monotocous species), the relevant contribution of the rat model to human labour pain, and the current clinical and experimental knowledge of parturition pain mechanisms in domestic animals that support the fact that domestic polytocous species also experience pain. Moreover, both for women and domestic animal species, parturition's pain represents a potential welfare concern, and information on pain indicators and the appropriate analgesic therapy are discussed.

Efficacy and safety of non-pharmacological interventions for labour pain management: A systematic review and Bayesian network meta-analysis

AIMS AND OBJECTIVES

To compare and rank the efficacy and safety of non-pharmacological interventions in the management of labour pain.

BACKGROUND

Recently, various non-pharmacological interventions have been applied to manage labour pain and have shown positive effects. However, evidence identifying which type of non-pharmacological intervention is more efficient and safer is limited.

DESIGN

Systematic review and Bayesian network meta-analysis based on PRISMA-NMA.

METHODS

Seven databases were searched from database inception-March 2020. Two reviewers independently performed study selection, quality appraisal and data extraction. Conventional meta-analysis was conducted using either fixed-effects model or random-effects model according to statistical heterogeneity. The Bayesian network meta-analysis was conducted using the consistency model.

RESULTS

43 studies involving nine non-pharmacological interventions were included. The Bayesian network meta-analysis showed that acupressure (SMD = -2.00, 95% CrI -3.09 to -0.94), aromatherapy (SMD = -2.01, 95% CrI -3.70 to -0.35) and massage therapy (SMD = -1.26, 95% CrI -2.26 to -0.30) had significant positive effects on alleviating labour pain, with aromatherapy being the most effective. The results also revealed that yoga (SMD = -130.85, 95% CrI -212.01 to -59.32) and acupressure (SMD = -10.14, 95% CrI -20.24 to -0.41) were the most effective interventions for shortening the first stage and the second stage of labour, respectively. There were no significant differences between non-pharmacological interventions and usual care or placebo control on the use of pharmacological methods and neonatal 5-min Apgar score.

CONCLUSIONS

The evidence in this network meta-analysis illustrates that non-pharmacological interventions are effective and safe for labour pain management in low-risk pregnant women. In the future, well-designed studies are needed to validate the conclusion of this network meta-analysis.

RELEVANCE TO CLINICAL PRACTICE

The results support the use of non-pharmacological interventions, especially aromatherapy and acupressure, to relieve labour pain in low-risk pregnant women. Non-pharmacological interventions for labour pain management are recommended to apply according to maternal women's preference and values.

Development of the Labor Pain Relief Attitude Questionnaire for pregnant women (LPRAQ-p)

BACKGROUND

Receiving epidural analgesia during labor can possibly have negative consequences for mother and child. Yet, the use of epidural analgesia rapidly increased in the Netherlands over the last decade. Since antenatal plans for labor pain relief have been related to epidural analgesia use during labor, the aim of the current study was to develop a Labor Pain Relief Attitude Questionnaire for pregnant women (LPRAQ-p).

METHODS

Three focus group interviews were conducted with pregnant women, new mothers and caregivers and 13 candidate items were derived. Psychometric properties were tested with explorative factor analysis in sample I (N = 429) and a subsequent confirmatory factor analysis in a different sample II (N = 432).

RESULTS

The explorative factor analysis suggested a two-factor seven-item solution: a 'women's perception' and 'social environment' subscale. The confirmatory factor analysis confirmed an excellent six-item model fit with appropriate internal consistency. Higher scores on the six-item LPRAQ-p indicate greater willingness for request of pain relief medication during labor. Two-tailed t-tests showed that women with elevated levels of depression and pregnancy-specific distress symptoms, nulliparous women and multiparous women with complications during a previous delivery had greater willingness for request of pain relief medication during labor. Linear regression showed that the most important association with higher scores on the LPRAQ-p were high pregnancy-specific distress symptoms.

CONCLUSIONS

This study showed the LPRAQ-p to be a valid instrument to evaluate attitude towards labor pain relief in pregnant women. High scores on this questionnaire are associated with high levels of pregnancy-specific distress symptoms.

Effects of different analgesic methods used for vaginal delivery on mothers and fetuses

Background/aim

Knowledge regarding pain relief during labor remains insufficient. We aimed to determine and compare the effectiveness and safety of epidural analgesia, combined spinal–epidural analgesia, and parenteral meperidine on both mothers and fetuses.

Materials and methods

This study was designed as an observational case-control study. We collected prospective data from patients whose labor pain management was conducted with meperidine in addition to retrospective cohort data of neuraxial methods; 138 patients were enrolled. Epidural analgesia group consisted of 68 patients, whereas combined spinal-epidural (CSE) analgesia group and meperidine group consisted of 50 and 20 patients, respectively. We compared the delivery patterns, labor durations, pain levels, side effects, maternal satisfaction levels, and neonatal outcomes of the various pain management methods.

Results

Patient demographics, duration of first, second, and third labor stages, and instrumental delivery rates were comparable among groups (P > 0.05). Cesarean section tended to be less frequent in the CSE group. In the meperidine group, visual analog scale (VAS) values and sedation were significantly higher (P < 0.001) and maternal satisfaction lower (P < 0.001). Hypotension tended to be more frequent in the meperidine group. APGAR scores at the 1st and 5th min were similar among the groups and between meperidine subgroups defined by three different administration times (<1 h, 1‒4 h, ≥4 h; P > 0.05).

Conclusion

Neuraxial methods had no effect on instrumental delivery rates. CSE represented a near significant risk reduction in cesarean section. Our results demonstrated that regional analgesia methods were reasonably safe for both mother and fetus, and regional analgesia methods resulted in greater maternal satisfaction and pain control compared to meperidine.

Birthing Consciousness as a Case of Adaptive Altered State of Consciousness Associated With Transient Hypofrontality

In this article, I present the concept of “birthing consciousness,” a psychophysical altered state of women that can occur during natural and undisturbed birth. I demonstrate that this altered state of consciousness (ASC) has phenomenological and cognitive features of hypofrontality; thus, birthing consciousness probably shares a similar brain mechanism to that postulated by the transient-hypofrontality theory (THT). I argue that until recently (with the advent of modern medical intervention), in evolutionary terms, women lacking the proclivity for this specific brain mechanism had a lower chance of reproducing successfully. Hence, I suggest a general and preliminary hypothesis concerning THT: Birthing consciousness is one example of an adaptive pain-induced ASC associated with transient hypofrontality.

Labour Q1 pain - poorly analysed and reported: a systematic review

Background

Modelling and analysing repeated measures data, such as women’s experiences of pain during labour, is a complex topic. Traditional end-point analyses such as t-tests, ANOVA, or repeated measures [rANOVA] have known disadvantages. Modern and more sophisticated statistical methods such as mixed effect models provide flexibility and are more likely to draw correct conclusions from data. The aim of this study is to study how labour pain is analysed in repeated measures design studies, and to increase awareness of when and why modern statistical methods are suitable with the aim of encouraging their use in preference of traditional methods.

Methods

Six databases were searched with the English language as a restriction. Study eligibility criteria included: Original studies published between 1999 and 2016, studying pregnant women in labour with the aim to compare at least two methods for labour pain management, with at least two measurements of labour pain separated by time, and where labour pain was analysed.

After deduplication, all records (n = 2800) were screened by one of the authors who excluded ineligible publication types, leaving 737 records remaining for full-text screening. A sample of 309 studies was then randomly selected and screened by both authors.

Results

Among the 133 (of 309) studies that fulfilled the study eligibility criteria, 7% used mixed effect models, 20% rANOVA, and 73% used end-point analysis to draw conclusions regarding treatment effects for labour pain between groups. The most commonly used end-point analyses to compare groups regarding labour pain were t-tests (57, 43%) and ANOVA (41, 31%). We present a checklist for clinicians to clarify when mixed effect models should be considered as the preferred choice for analysis, in particular when labour pain is measured.

Conclusions

Studies that aim to compare methods for labour pain management often use inappropriate statistical methods, and inaccurately report how the statistical analyses were carried out. The statistical methods used in analyses are often based on assumptions that are not fulfilled or described. We recommend that authors, reviewers, and editors pay greater attention to the analysis when designing and publishing studies evaluating methods for pain relief during labour.

Electronic supplementary material

The online version of this article (10.1186/s12884-018-2089-2) contains supplementary material, which is available to authorized users.

Labor pain in women with and without severe fear of childbirth: A population-based, longitudinal study

BACKGROUND

This prospective study aims to investigate whether severe fear of childbirth increases pain perceptions during birth and whether co-occurring maternal health and birth factors as well as length and weight of the child explain the association.

METHODS

The study sample comprised women with a vaginal delivery and was drawn from the Akershus Birth Cohort. Data from the hospital birth's record and questionnaires at weeks 17-19 and 32 of pregnancy and 8 weeks postpartum were used (n = 1649). Analysis of variance and analysis of covariance were conducted to examine whether ratings of labor pain differed significantly between women with and without severe fear of childbirth and which factors explained the difference.

RESULTS

Women with severe fear of childbirth experienced significantly more labor pain than women without severe fear of childbirth (P < .01). However, when controlling for symptoms of maternal depression and anxiety, use of epidural/spinal anesthetic or nitrous oxide gas, and menstrual pain, this difference was no longer significant (P = .09).

DISCUSSION

Although the results show that labor pain is related to multiple physiological and psychological factors in a complex manner, symptoms of maternal depression and anxiety seem to play a central role for the experience of labor pain, and should therefore be focused on by health practitioners.

Epidural versus non-epidural or no analgesia for pain management in labour

BACKGROUND

Epidural analgesia is a central nerve block technique achieved by injection of a local anaesthetic close to the nerves that transmit pain, and is widely used as a form of pain relief in labour. However, there are concerns about unintended adverse effects on the mother and infant. This is an update of an existing Cochrane Review (Epidural versus non-epidural or no analgesia in labour), last published in 2011.

OBJECTIVES

To assess the effectiveness and safety of all types of epidural analgesia, including combined-spinal-epidural (CSE) on the mother and the baby, when compared with non-epidural or no pain relief during labour.

SEARCH METHODS

We searched Cochrane Pregnancy and Childbirth's Trials Register (ClinicalTrials.gov), the WHO International Clinical Trials Registry Platform (ICTRP) (30 April 2017), and reference lists of retrieved studies.

SELECTION CRITERIA

Randomised controlled trials comparing all types of epidural with any form of pain relief not involving regional blockade, or no pain relief in labour. We have not included cluster-randomised or quasi-randomised trials in this update.

DATA COLLECTION AND ANALYSIS

Two review authors independently assessed trials for inclusion and risks of bias, extracted data and checked them for accuracy. We assessed selected outcomes using the GRADE approach.

MAIN RESULTS

Fifty-two trials met the inclusion criteria and we have included data from 40 trials, involving over 11,000 women. Four trials included more than two arms. Thirty-four trials compared epidural with opioids, seven compared epidural with no analgesia, one trial compared epidural with acu-stimulation, one trial compared epidural with inhaled analgesia, and one trial compared epidural with continuous midwifery support and other analgesia. Risks of bias varied throughout the included studies; six out of 40 studies were at high or unclear risk of bias for every bias domain, while most studies were at high or unclear risk of detection bias. Quality of the evidence assessed using GRADE ranged from moderate to low quality.Pain intensity as measured using pain scores was lower in women with epidural analgesia when compared to women who received opioids (standardised mean difference -2.64, 95% confidence interval (CI) -4.56 to -0.73; 1133 women; studies = 5; I2 = 98%; low-quality evidence) and a higher proportion were satisfied with their pain relief, reporting it to be "excellent or very good" (average risk ratio (RR) 1.47, 95% CI 1.03 to 2.08; 1911 women; studies = 7; I2 = 97%; low-quality evidence). There was substantial statistical heterogeneity in both these outcomes. There was a substantial decrease in the need for additional pain relief in women receiving epidural analgesia compared with opioid analgesia (average RR 0.10, 95% CI 0.04 to 0.25; 5099 women; studies = 16; I2 = 73%; Tau2 = 1.89; Chi2 = 52.07 (P < 0.00001)). More women in the epidural group experienced assisted vaginal birth (RR 1.44, 95% CI 1.29 to 1.60; 9948 women; studies = 30; low-quality evidence). A post hoc subgroup analysis of trials conducted after 2005 showed that this effect is negated when trials before 2005 are excluded from this analysis (RR 1.19, 95% CI 0.97 to 1.46). There was no difference between caesarean section rates (RR 1.07, 95% CI 0.96 to 1.18; 10,350 women; studies = 33; moderate-quality evidence), and maternal long-term backache (RR 1.00, 95% CI 0.89 to 1.12; 814 women; studies = 2; moderate-quality evidence). There were also no clear differences between groups for the neonatal outcomes, admission to neonatal intensive care unit (RR 1.03, 95% CI 0.95 to 1.12; 4488 babies; studies = 8; moderate-quality evidence) and Apgar score less than seven at five minutes (RR 0.73, 95% CI 0.52 to 1.02; 8752 babies; studies = 22; low-quality evidence). We downgraded the evidence for study design limitations, inconsistency, imprecision in effect estimates, and possible publication bias.Side effects were reported in both epidural and opioid groups. Women with epidural experienced more hypotension, motor blockade, fever, and urinary retention. They also had longer first and second stages of labour, and were more likely to have oxytocin augmentation than the women in the opioid group. Women receiving epidurals had less risk of respiratory depression requiring oxygen, and were less likely to experience nausea and vomiting than women receiving opioids. Babies born to women in the epidural group were less likely to have received naloxone. There was no clear difference between groups for postnatal depression, headache, itching, shivering, or drowsiness. Maternal morbidity and long-term neonatal outcomes were not reported.Epidural analgesia resulted in less reported pain when compared with placebo or no treatment, and with acu-stimulation. Pain intensity was not reported in the trials that compared epidural with inhaled analgesia, or continuous support. Few trials reported on serious maternal side effects.

AUTHORS' CONCLUSIONS

Low-quality evidence shows that epidural analgesia may be more effective in reducing pain during labour and increasing maternal satisfaction with pain relief than non-epidural methods. Although overall there appears to be an increase in assisted vaginal birth when women have epidural analgesia, a post hoc subgroup analysis showed this effect is not seen in recent studies (after 2005), suggesting that modern approaches to epidural analgesia in labour do not affect this outcome. Epidural analgesia had no impact on the risk of caesarean section or long-term backache, and did not appear to have an immediate effect on neonatal status as determined by Apgar scores or in admissions to neonatal intensive care. Further research may be helpful to evaluate rare but potentially severe adverse effects of epidural analgesia and non-epidural analgesia on women in labour and long-term neonatal outcomes.

Kinesiologic tape for labor pain control: Randomized controlled trial

Background: Kinesiologic taping has been studied for managing diverse types of dysfunctions and pain, but not for managing pain during labor. Objective: This study evaluated the effectiveness and safety of using kinesiologic tape (KT) during labor relative to pain, maternal satisfaction, and obstetric and neonatal outcomes. Method: The study was a single-blind randomized controlled trial composed of 60 pregnant women divided into two groups. In the kinesiologic tape group (KTG), the tape was applied to the region of spinal nerves T10-L1 and S2-S4; in the control group (CG), the tape was applied to the region of spinal nerves T1-T4. Study participants were low-risk pregnant women with spontaneous onset of labor and no previous Cesarean section. Outcomes evaluated were pain, duration of labor, type of delivery, uterotonic and anesthetic requirement, neonatal vitality, and satisfaction with delivery and tape use. Intention-to-treat analysis was performed, and risk ratios with a 95% CI were estimated. Results: After the first hour of tape use, a significant increase in pain was observed in the CG (p = 0.002). However, there were no differences between groups relative to the remaining outcomes assessed. In the KTG, 59% of participants reported satisfaction with tape use, whereas in the CG, 44% reported satisfaction with tape use. Conclusion: Despite its safety, the KT technique did not prove to effectively control labor pain.

Kinesio Taping for pain control during labor: Protocol of a randomized, controlled trial

This study protocol will evaluate the effectiveness and safety during labor and delivery of the Kinesio Taping bandage for pain sensation, satisfaction of patients, and obstetric and neonatal outcomes. A randomized controlled trial with 60 participants divided into two groups will be conducted. The intervention group will receive bandage application on the vertebral regions corresponding to uterine dermatomes - from T10 to L1 and from S2 to S4. The control group will receive bandage application away from uterine dermatomes, from T1 to T4. The primary endpoint is pain during labor. Secondary endpoints are perinatal outcomes and patient satisfaction with the bandage and with her labor. Pain levels will be evaluated on an hourly basis during labor, and intention-to-treat analysis will be performed. Risk ratios and 95% confidence intervals will be calculated. Findings on effectiveness of pain control with no adverse effects to both the mother and neonate are the first step in evaluating the systematic use of Kinesio Taping during labor. Since self-control may affect birthing experience satisfaction, discovering new alternatives for pain control may allow for a better experience.

Associations between maternal characteristics and women's responses to acupuncture during labour: a secondary analysis from a randomised controlled trial

Background

Patient characteristics are modulators of pain experience after acupuncture treatment for chronic pain. Whether this also applies to labour pain is unknown.

Aim

To examine for associations between maternal characteristics and response to acupuncture in terms of labour pain intensity in close proximity to the treatment (within 60 min) and over a longer time period (up to 240 min), and whether or not epidural analgesia is used, before and after adjustment for obstetric status upon admission to the labour ward.

Methods

Cohort study (n=253) using data collected for a randomised controlled trial. Associations were examined using linear mixed models and logistic regression analyses. Tests of interactions were also applied to investigate whether maternal characteristics were influenced by treatment group allocation.

Results

In close proximity to the treatment, advanced age and cervical dilation were associated with lower pain scores (mean difference (MD) −13.2, 95% CI −23.4 to −2.9; and MD −5.0, 95% CI −9.6 to −0.5, respectively). For the longer time period, labour pain was negatively associated with age (MD −11.8, 95% CI −19.6 to −3.9) and positively associated with dysmenorrhoea (MD 5.5, 95% CI 1.6 to 9.5). Previous acupuncture experience and advanced cervical dilatation were associated with higher and lower use of epidural analgesia (OR 2.7, 95% CI 1.3 to 5.9; and OR 0.3, 95% CI 0.1 to 0.5, respectively). No interactions with treatment allocation were found.

Conclusions

This study did not identify any maternal characteristics associated with women's responses to acupuncture during labour.

Trial registration number

NCT01197950; Post-results.

Depressed mood, anxiety, and the use of labor analgesia

Relatively little is known about mental health and labor pain. The aim of this study was to assess if self-rated antenatal depressed mood and anxiety are associated with pain-related behaviors and self-reported labor pain. We also wanted to replicate our previous finding of altered labor pain behavior in carriers of a specific guanosine triphosphate cyclohydrolase 1 gene (GCH1) haplotype. Ninety-nine women in gestational weeks 37 to 40 filled out questionnaires on depression and anxiety symptoms and later rated their labor pain by use of visual analog scales. Each subject was also genotyped for GCH1. Following adjustment for relevant confounders, women who arrived early to the delivery unit (cervical dilation <5 cm) had a significantly higher antenatal Montgomery-Åsberg Depression Rating Scale (MADRS-S) score, p < 0.05, than late arrivers (cervical dilation >5 cm). Women with increased Spielberger State-Trait Anxiety Inventory (STAI-T) scores reported higher self-rated pain prior to labor analgesia, p < 0.05, than women with low STAI-T scores. No association between the GCH1 pain-protective haplotype and cervical dilation was found, but a previously demonstrated association with increased use of second-line analgesia was confirmed. Depressed mood during pregnancy is associated with early arrival to the delivery department, whereas antenatal anxiety is associated with increased self-rated pain prior to labor analgesia.

Bupivacaine in combination with fentanyl or sufentanil in epidural/intrathecal analgesia for labor: a meta-analysis

This study is to compare the effectiveness of combinational use of bupivacaine with fentanyl (BUPI-FEN) and sufentanil (BUPI-SUF) in epidural/intrathecal analgesia for labor. Electronic databases were searched for relevant research papers published between 1985 and 2014. Meta-analyses of mean differences or odds ratios were performed and statistical heterogeneity between the studies tested by I(2) index. Ten studies recruiting a total of 728 women in labor were selected. Concentrations of the anesthetics used as mean ± sd were bupivacaine 0.115 ± 0.056%, fentanyl 0.0007 ± 0.001%, and sufentanil 0.00017 ± 0.00022%. Duration of analgesia was not significantly different between BUPI-SUF and BUPI-FEN administered mothers (mean difference [95%CI] of -33.55 [-74.94, 7.83] minutes; P = .11) under random effects. The onset of analgesia was also not significantly different between both groups (mean difference [95%CI] of -0.61 [-1.38, 0.16] minutes; P = .12). The number of neonates with Apgar score < 7 was significantly lower in BUPI-FEN group (odd ratio [95%CI] of 0.31 [0.10, 0.95]; P < .05). Pruritus incidence was similar. In conclusion, BUPI-FEN combination exhibits significantly better tolerability at an approximate ratio of 6 FEN:1 SUF, albeit, both fentanyl and sufentanil in combination with bupivacaine provide similar analgesic properties via the epidural or intrathecal routes for labor pain relief.

Epidural versus non-epidural or no analgesia in labour

BACKGROUND

Epidural analgesia is a central nerve block technique achieved by injection of a local anaesthetic close to the nerves that transmit pain and is widely used as a form of pain relief in labour. However, there are concerns regarding unintended adverse effects on the mother and infant.

OBJECTIVES

To assess the effects of all modalities of epidural analgesia (including combined-spinal-epidural) on the mother and the baby, when compared with non-epidural or no pain relief during labour.

SEARCH METHODS

We searched the Cochrane Pregnancy and Childbirth Group's Trials Register (31 March 2011).

SELECTION CRITERIA

Randomised controlled trials comparing all modalities of epidural with any form of pain relief not involving regional blockade, or no pain relief in labour.

DATA COLLECTION AND ANALYSIS

Two of the review authors independently assessed trials for eligibility, methodological quality and extracted all data. We entered data into RevMan and double checked it for accuracy. Primary analysis was by intention to treat; we conducted subgroup and sensitivity analyses where substantial heterogeneity was evident.

MAIN RESULTS

We included 38 studies involving 9658 women; all but five studies compared epidural analgesia with opiates. Epidural analgesia was found to offer better pain relief (mean difference (MD) -3.36, 95% confidence interval (CI) -5.41 to -1.31, three trials, 1166 women); a reduction in the need for additional pain relief (risk ratio (RR) 0.05, 95% CI 0.02 to 0.17, 15 trials, 6019 women); a reduced risk of acidosis (RR 0.80, 95% CI 0.68 to 0.94, seven trials, 3643 women); and a reduced risk of naloxone administration (RR 0.15, 95% CI 0.10 to 0.23, 10 trials, 2645 women). However, epidural analgesia was associated with an increased risk of assisted vaginal birth (RR 1.42, 95% CI 1.28 to 1.57, 23 trials, 7935 women), maternal hypotension (RR 18.23, 95% CI 5.09 to 65.35, eight trials, 2789 women), motor-blockade (RR 31.67, 95% CI 4.33 to 231.51, three trials, 322 women), maternal fever (RR 3.34, 95% CI 2.63 to 4.23, six trials, 2741 women), urinary retention (RR 17.05, 95% CI 4.82 to 60.39, three trials, 283 women), longer second stage of labour (MD 13.66 minutes, 95% CI 6.67 to 20.66, 13 trials, 4233 women), oxytocin administration (RR 1.19, 95% CI 1.03 to 1.39, 13 trials, 5815 women) and an increased risk of caesarean section for fetal distress (RR 1.43, 95% CI 1.03 to 1.97, 11 trials, 4816 women). There was no evidence of a significant difference in the risk of caesarean section overall (RR 1.10, 95% CI 0.97 to 1.25, 27 trials, 8417 women), long-term backache (RR 0.96, 95% CI 0.86 to 1.07, three trials, 1806 women), Apgar score less than seven at five minutes (RR 0.80, 95% CI 0.54 to 1.20, 18 trials, 6898 women), and maternal satisfaction with pain relief (RR 1.31, 95% CI 0.84 to 2.05, seven trials, 2929 women). We found substantial heterogeneity for the following outcomes: pain relief; maternal satisfaction; need for additional means of pain relief; length of second stage of labour; and oxytocin augmentation. This could not be explained by subgroup or sensitivity analyses, where data allowed analysis. No studies reported on rare but potentially serious adverse effects of epidural analgesia.

AUTHORS' CONCLUSIONS

Epidural analgesia appears to be effective in reducing pain during labour. However, women who use this form of pain relief are at increased risk of having an instrumental delivery. Epidural analgesia had no statistically significant impact on the risk of caesarean section, maternal satisfaction with pain relief and long-term backache and did not appear to have an immediate effect on neonatal status as determined by Apgar scores. Further research may be helpful to evaluate rare but potentially severe adverse effects of epidural analgesia on women in labour and long-term neonatal outcomes.

Different SNP combinations in the GCH1 gene and use of labor analgesia

Background

The aim of this study was to investigate if there is an association between different SNP combinations in the guanosine triphosphate cyclohydrolase (GCH1) gene and a number of pain behavior related outcomes during labor. A population-based sample of pregnant women (n = 814) was recruited at gestational week 18. A plasma sample was collected from each subject. Genotyping was performed and three single nucleotide polymorphisms (SNP) previously defined as a pain-protective SNP combination of GCH1 were used.

Results

Homozygous carriers of the pain-protective SNP combination of GCH1 arrived to the delivery ward with a more advanced stage of cervical dilation compared to heterozygous carriers and non-carriers. However, homozygous carriers more often used second line labor analgesia compared to the others.

Conclusion

The pain-protective SNP combination of GCH1 may be of importance in the limited number of homozygous carriers during the initial dilation of cervix but upon arrival at the delivery unit these women are more inclined to use second line labor analgesia.

Influence of pregnancy and labor on the occurrence of nerve fibers expressing the capsaicin receptor TRPV1 in human corpus and cervix uteri

BACKGROUND

Cervical ripening is a prerequisite for a normal obstetrical outcome. This process, including labor, is a painful event that shares features with inflammatory reactions where peripheral nociceptive pathways are involved. The capsaicin and heat receptor TRPV1 is a key molecule in sensory nerves involved in peripheral nociception, but little is known regarding its role in the pregnant uterus. Therefore, the aim of this study was to investigate human corpus and cervix uteri during pregnancy and labor and non-pregnant controls for the presence of TRPV1.

METHODS

We have investigated human uterine corpus and cervix biopsies at term pregnancy and parturition. Biopsies were taken from the upper edge of the hysterotomy during caesarean section at term (n = 8), in labor (n = 8) and from the corresponding area in the non-pregnant uterus after hysterectomy (n = 8). Cervical biopsies were obtained transvaginally from the anterior cervical lip. Serial frozen sections were examined immunohistochemically using specific antibodies to TRPV1 and nerve markers (neurofilaments/peripherin).

RESULTS

In cervix uteri, TRPV1-immunoreactive fibers were scattered throughout the stroma and around blood vessels, and appeared more frequent in the sub-epithelium. Counts of TRPV1-immunoreactive nerve fibers were not significantly different between the three groups. In contrast, few TRPV1-immunoreactive fibers were found in nerve fascicles in the non-pregnant corpus, and none in the pregnant corpus.

CONCLUSION

In this study, TRPV1 innervation in human uterus during pregnancy and labor is shown for the first time. During pregnancy and labor there was an almost complete disappearance of TRPV1 positive nerve fibers in the corpus. However, cervical innervation remained throughout pregnancy and labor. The difference in TRPV1 innervation between the corpus and the cervix is thus very marked. Our data suggest that TRPV1 may be involved in pain mechanisms associated with cervical ripening and labor. Furthermore, these data support the concept that cervix uteri may be the major site from which labor pain emanates. Our findings also support the possibility of developing alternative approaches to treat labor pain.

Glutamate and metabotropic glutamate receptors associated with innervation of the uterine cervix during pregnancy: Receptor antagonism inhibits c-fos expression in rat lumbosacral spinal cord at parturition

Dorsal root ganglia (DRG) neurons connect the spinal cord and uterine cervix, and are activated at parturition with subsequent stimulation of secondary neurons in the spinal dorsal horn and autonomic areas. Neuropeptide neurotransmitters and receptors have been studied in these areas, but amino acid transmitters, e.g., glutamate, an excitatory neurotransmitter involved in sensory and nociceptive processing, have not been characterized. To determine if glutamate is involved in innervation of the cervix, rats were examined for markers of glutamatergic neurons in the L6-S1 spinal cord, DRG and cervix. Metabotropic glutamate receptors mGluR5 in the spinal dorsal horn and their expression over pregnancy were examined in pregnant rats and pregnant rats treated continuously with an antagonist of mGluR5, 2-methyl-6-(phenylethynyl) pyridine (MPEP). Rats were allowed to deliver pups to determine if the antagonist altered the expression of an early response gene protein, Fos, in the L6-S1 cord. Immunohistochemistry showed glutamate- and vesicular glutamate transporter1 (VGluT1)-positive fibers in the cervix, glutamate- and VGluT1-expressing neurons in the DRG, some of which also exhibited retrograde tracer from cervical injections, and VGluT1 and mGluR5 immunoreactivities in the L6-S1 spinal dorsal horns. Expression of mGluR5 receptors increased over pregnancy. Fos-positive neurons were present among mGluR5-immunoreactivity in the spinal dorsal horn. Parturition-induced Fos-positive neurons in the spinal cords were abundant in control rats, but were reduced by 70% in MPEP-treated animals. These results suggest that glutamate is likely involved in the transmission of sensory signals, possibly pain, from the cervix to the spinal cord at parturition.

Epidural versus non-epidural or no analgesia in labour

BACKGROUND

Epidural analgesia is a central nerve block technique achieved by injection of a local anaesthetic close to the nerves that transmit pain and is widely used as a form of pain relief in labour. However, there are concerns regarding unintended adverse effects on the mother and infant.

OBJECTIVES

To assess the effects of all modalities of epidural analgesia (including combined -spinal-epidural) on the mother and the baby, when compared with non-epidural or no pain relief during labour.

SEARCH STRATEGY

We searched the Cochrane Pregnancy and Childbirth Group Trials Register (June 2005).

SELECTION CRITERIA

Randomised controlled trials comparing all modalities of epidural with any form of pain relief not involving regional blockade, or no pain relief in labour.

DATA COLLECTION AND ANALYSIS

Two of the review authors independently assessed trials for eligibility, methodological quality and extracted all data. Data were entered into RevMan and double checked. Primary analysis was by intention-to-treat; sensitivity analyses excluded trials with > 30% of women receiving un-allocated treatment.

MAIN RESULTS

Twenty-one studies involving 6664 women were included, all but one study compared epidural analgesia with opiates. For technical reasons, data on women's perception of pain relief in labour could only be included from one study which found epidural analgesia to offer better pain relief than non-epidural analgesia (weighted mean difference (WMD) -2.60, 95% confidence interval (CI) -3.82 to -1.38, 1 trial, 105 women). However, epidural analgesia was associated with an increased risk of instrumental vaginal birth (relative risk (RR) 1.38, 95% CI 1.24 to 1.53, 17 trials, 6162 women). There was no evidence of a significant difference in the risk of caesarean delivery (RR 1.07, 95% CI 0.93 to 1.23, 20 trials, 6534 women), long-term backache (RR 1.00, 95% CI 0.89 to 1.12, 2 trials, 814 women), low neonatal Apgar scores at five minutes (RR 0.70, 95% CI 0.44 to 1.10, 14 trials, 5363 women), and maternal satisfaction with pain relief (RR 1.18 95% CI 0.92 to 1.50, 5 trials, 1940 women). No studies reported on rare but potentially serious adverse effects of epidural analgesia.

AUTHORS' CONCLUSIONS

Epidural analgesia appears to be effective in reducing pain during labour. However, women who use this form of pain relief are at increased risk of having an instrumental delivery. Epidural analgesia had no statistically significant impact on the risk of caesarean section, maternal satisfaction with pain relief and long-term backache and did not appear to have an immediate effect on neonatal status as determined by Apgar scores. Further research may be helpful to evaluate rare but potentially severe adverse effects of epidural analgesia on women in labour and long-term neonatal outcomes.

Unaltered innervation of the human cervix uteri in contrast to the corpus during pregnancy and labor as revealed by PGP 9.5 immunohistochemistry

OBJECTIVE

To examine the occurrence of the general neuronal marker protein gene product 9.5 (PGP 9.5) in the human corpus (isthmus region) and the cervix uteri during pregnancy and parturition

STUDY DESIGN

Biopsies were taken from the upper edge of the hysterotomy during caesarean section (CS) at term (n=5), in labor (n=5) and from the corresponding area in the non-pregnant uterus after hysterectomy (n=5). Cervical biopsies were obtained transvaginally from the anterior cervical lip. Serial cryostate sections were prepared for immunohistochemistry using polyclonal antibodies to PGP 9.5.

RESULTS

Nerve fibers displaying PGP 9.5 immunoreactivity were observed in all sections from the three groups examined. They were identified in muscle tissue, in the stroma, and around blood vessel walls. A 30-fold decline of immunoreactive nerve fibers was observed in the isthmus part of the corpus uteri at term compared to the non-pregnant. There were no significant differences between the immunoreactivity in the cervix uteri of the three groups

CONCLUSIONS

The innervation of the cervix uteri is dense and unaltered throughout pregnancy and labor. In contrast, the corpus is almost denervated. Further studies are needed to clarify the reason and the impact of these findings.

[Corticotrophin hormone serum levels of parturients submitted to nonpharmacologic anxiety and pain relief method during labor]

This study aimed to analyze the plasma ACTH levels and the correlation between the ACTH levels and pain and anxiety during parturition. Seventeen parturients received routine nursing care (control group--CG) and nineteen (Experimental Group--EG) were stimulated and guided to perform respiration and relaxation techniques. ACTH levels, pain intensity and state-trait anxiety were evaluated. ACTH levels were lower at the beginning of labor, peaked at the end and decreased again in the immediate postpartum period. There was no significant statistical difference between the groups. Lower ACTH levels and partial stress relief in the EG suggest the interference of breathing and relaxation techniques; ACTH levels did not show any correlation with anxiety or pain in any of both groups.

Utilização de técnicas de respiração e relaxamento para alívio de dor e ansiedade no processo de parturição

Objetivou-se avaliar o efeito de técnicas de respiração e de relaxamento sobre a dor e a ansiedade, na parturição. Dezessete primigestas (grupo controle - GC) receberam assistência de rotina e dezenove (grupo experimental - GE) foram orientadas e estimuladas a realizar técnicas de respiração e relaxamento. Avaliou-se a dor, através da escala analógica visual, e a ansiedade, através dos inventários de ansiedade-traço e estado. A intensidade de dor aumentou com a evolução do trabalho de parto para ambos os grupos. O nível de ansiedade na fase latente foi baixo para ambos os grupos; na fase ativa foi médio para o GC e baixo para o GE; na fase de transição foi médio e, no pós-parto, imediato, foi baixo, para ambos os grupos. Concluiu-se que as técnicas utilizadas não reduziram a intensidade de dor, mas promoveram ao GE a manutenção de nível baixo de ansiedade por maior tempo da parturição.