A randomized controlled trial of a new treatment for labor dystocia

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.

Investigating the role of CFTR in human and mouse myometrium

Background

Abnormal cystic fibrosis transmembrane conductance regulator (CFTR) function in cystic fibrosis (CF) has been linked to airway smooth muscle abnormalities including bronchial hyperresponsiveness. However, a role for CFTR in other types of smooth muscle, including myometrium, remains largely unexplored. As CF life expectancy and the number of pregnancies increases, there is a need for an understanding of the potential role of CFTR in myometrial function.

Methods

We investigated the role of CFTR in human and mouse myometrium. We used immunofluorescence to identify CFTR expression, and carried out contractility studies on spontaneously contracting term pregnant and non-pregnant mouse myometrium and term pregnant human myometrial biopsies from caesarean sections.

Results

CFTR was found to be expressed in term pregnant mouse myometrium. Inhibition of CFTR, with the selective inhibitor CFTRinh-172, significantly reduced contractility in pregnant mouse and human myometrium in a concentration-dependent manner (44.89 ± 11.02 term pregnant mouse, 9.23 ± 4.75 term-pregnant human; maximal effect at 60 μM expressed as a percentage of the pre-treatment control period). However, there was no effect of CFTRinh-172 in non-pregnant myometrium.

Conclusion

These results demonstrate decreased myometrial function when CFTR is inhibited, which may have implications on pregnancy and labour outcome and therapeutic decisions for labour in CF patients.

Factors associated with spontaneous vaginal birth in nulliparous women: A descriptive systematic review

PROBLEM

Spontaneous vaginal birth (SVB) rates for nulliparous women are declining internationally.

BACKGROUND

There is inadequate understanding of factors affecting this trend overall and limited large-scale responses to improve women's opportunity to birth spontaneously.

AIM

To undertake a descriptive systematic review identifying factors associated with spontaneous vaginal birth at term, in nulliparous women with a singleton pregnancy.

METHODS

Quantitative studies of all designs, of nulliparous women with a singleton pregnancy and cephalic presentation, who experienced a SVB at term were included. Nine databases were searched (inception to October 2022). Two reviewers undertook quality appraisal; Randomised Controlled Trials (RCTs) with high risk of bias (ROB 2.0) and other designs with (QATSDD) scoring ≤ 50% were excluded.

FINDINGS

Data were abstracted from 90 studies (32 RCTs, 39 cohort, 9 cross-sectional, 4 prevalence, 5 case control, 1 quasi-experimental). SVB rates varied (13%-99%). Modifiable factors associated with SVB included addressing fear of childbirth, low impact antenatal exercise, maternal positioning during second-stage labour and midwifery led care. Complexities arising during pregnancy and regional analgesia were shown to decrease SVB and other interventions, such as routine induction of labour were equivocal.

DISCUSSION

Antenatal preparation (low impact exercise, childbirth education, addressing fear of childbirth) may increase SVB, as does midwifery continuity-of-care. Intrapartum strategies to optimise labour progression emerged as promising areas for further research.

CONCLUSION

Declining SVB rates may be improved through multi-factorial approaches inclusive of maternal, fetal and clinical care domains. However, the variability of SVB rates testifies to the complexity of the issue.

Maternal and newborn plasma oxytocin levels in response to maternal synthetic oxytocin administration during labour, birth and postpartum - a systematic review with implications for the function of the oxytocinergic system

BACKGROUND

The reproductive hormone oxytocin facilitates labour, birth and postpartum adaptations for women and newborns. Synthetic oxytocin is commonly given to induce or augment labour and to decrease postpartum bleeding.

AIM

To systematically review studies measuring plasma oxytocin levels in women and newborns following maternal administration of synthetic oxytocin during labour, birth and/or postpartum and to consider possible impacts on endogenous oxytocin and related systems.

METHODS

Systematic searches of PubMed, CINAHL, PsycInfo and Scopus databases followed PRISMA guidelines, including all peer-reviewed studies in languages understood by the authors. Thirty-five publications met inclusion criteria, including 1373 women and 148 newborns. Studies varied substantially in design and methodology, so classical meta-analysis was not possible. Therefore, results were categorized, analysed and summarised in text and tables.

RESULTS

Infusions of synthetic oxytocin increased maternal plasma oxytocin levels dose-dependently; doubling the infusion rate approximately doubled oxytocin levels. Infusions below 10 milliunits per minute (mU/min) did not raise maternal oxytocin above the range observed in physiological labour. At high intrapartum infusion rates (up to 32 mU/min) maternal plasma oxytocin reached 2-3 times physiological levels. Postpartum synthetic oxytocin regimens used comparatively higher doses with shorter duration compared to labour, giving greater but transient maternal oxytocin elevations. Total postpartum dose was comparable to total intrapartum dose following vaginal birth, but post-caesarean dosages were higher. Newborn oxytocin levels were higher in the umbilical artery vs. umbilical vein, and both were higher than maternal plasma levels, implying substantial fetal oxytocin production in labour. Newborn oxytocin levels were not further elevated following maternal intrapartum synthetic oxytocin, suggesting that synthetic oxytocin at clinical doses does not cross from mother to fetus.

CONCLUSIONS

Synthetic oxytocin infusion during labour increased maternal plasma oxytocin levels 2-3-fold at the highest doses and was not associated with neonatal plasma oxytocin elevations. Therefore, direct effects from synthetic oxytocin transfer to maternal brain or fetus are unlikely. However, infusions of synthetic oxytocin in labour change uterine contraction patterns. This may influence uterine blood flow and maternal autonomic nervous system activity, potentially harming the fetus and increasing maternal pain and stress.

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.

Pharmacological Interventions in Labor and Delivery

While there is not a wide range of pregnancy-specific drugs, there are some very specific high-risk areas of obstetric care for which unique pharmacological approaches have been established. In preterm birth, labor induction and augmentation, and the management of postpartum hemorrhage, these pharmacological approaches have become the bedrock in managing some of the most common and problematic areas of antenatal and intrapartum care. In this review, we summarize the existing established and emerging evidence that supports and broadens these pharmacological approaches to obstetric management and its impact on clinical practice. It is clear that existing therapeutics are limited. They have largely been developed from our knowledge of the physiology of the myometrium and act on hormonal receptors and their signaling pathways or on ion channels influencing excitability. Newer drugs in development are mostly refinements of these two approaches, but novel agents from plants and improved formulations are also discussed.

Amniotomy and early oxytocin infusion vs amniotomy and delayed oxytocin infusion for labour augmentation amongst nulliparous women at term: A randomised controlled trial

OBJECTIVE

to compare the effect of amniotomy with early vs delayed oxytocin infusion on successful vaginal delivery.

DESIGN

randomised controlled trial of nulliparous women with spontaneous labour at term.

SETTING

labour suite of a university teaching hospital in Kuala Lumpur, Malaysia.

PARTICIPANTS

240 women were included (120 randomised into two arms).

INTERVENTIONS

the randomisation sequence was generated using a computer randomisation program in two blocks: oxytocin infused early following amniotomy; and oxytocin infused 2 h after amniotomy.

MEASUREMENTS AND FINDINGS

labour duration, mode of delivery, oxytocin dosage used, uterine hyperstimulation, postpartum haemorrhage, Apgar score and admission to the neonatal intensive care unit were recorded. No differences in vaginal delivery rate (62.9% vs 70.9%; p = 0.248) and second-stage labour were found between the early and delayed oxytocin infusion groups (21.2 ± 18.3 min vs 25.5 ± 19.9 min; p = 0.220). The mean interval from amniotomy to vaginal delivery was significantly shorter for the early group (5.8 ± 1.7 h vs 7.0 ± 1.9 h; p = 0.001), and more women in the early group delivered during/before the planned review at 4 h after amniotomy (53.6% vs 10.6%; p<0.001). Maximum oxytocin usage was lower in the early group (5.6 ± 4.4 mL/hour vs 6.8 ± 5.3 mL/hour; p = 0.104).

KEY CONCLUSIONS

early oxytocin augmentation following amniotomy could be employed in low-risk primigravida, given that it is associated with a shorter labour duration without jeopardising maternal or neonatal outcomes.

IMPLICATIONS FOR PRACTICE

low-risk primigravida benefit from early oxytocin infusion following amniotomy, and this can be offered as an additional practice in labour room care.

Amniotic fluid lactate (AFL): a new predictor of labor outcome in dystocic deliveries

PURPOSE OF THIS REVIEW

Even today, hundreds of thousands of women die or suffer high levels of morbidity associated with childbirth. One of the most common causes is halted labor progress, or labor dystocia. There have been no developments in the diagnosis or treatment of dystocic deliveries since Friedman designed the Partogram in the 1950s. Oxytocin is the only treatment for dystocic labor. Sometimes, oxytocin is a lifesaver for the woman, especially in severe postpartum hemorrhages. At the same time, it is also one of the most overused drugs in obstetric care. This review article is meant to provide a short overview of the current knowledge of uterine metabolism during labor, uterine lactate production, and its association with labor dystocia. The article also intends to reflect new ways of thinking regarding practical recommendations for treating labor dystocia and offer a look at the future of dystocic labor management.

Body mass index and labor outcome associated with the level of amniotic fluid lactate. A cross-sectional study of women with labor dystocia

INTRODUCTION

Obesity is a globally growing problem. Labor dystocia is associated with obstetric complications, especially among obese pregnant women. Previous studies have shown an association between the level of lactate produced by uterine myocytes during contractions and the level of lactate in the amniotic fluid (AFL). A relationship between a high level of AFL and labor dystocia has also been demonstrated. However, it is still unknown whether the observation applies to all women with labor dystocia, regardless of body mass index (BMI). Aims: This study investigated whether there was any difference in the level of AFL in the three BMI groups and whether there was a difference in labor outcomes between high and low AFL in the different groups.

MATERIALS AND METHODS

This cross-sectional study included 1683 women from three different countries. Healthy nulliparous women in active labor were included, and they were grouped according to BMI as normal weighted (<25), overweight (≥25-29), and obese (≥30), respectively. AFL was categorized as high (≥10.1 mmol/l) and low (<10.1 mmol/l). The main outcome was the frequency of cesarean section.

RESULTS

No difference in AFL levels was found between the three BMI groups at delivery (mean values of 8.2 vs. 8.3 vs. 8.4 mmol/l, p = .3). Obese women with high AFL had a higher frequency of cesarean section than normal-weighted women (16.2 vs. 20.7 vs. 29.2%). Other risk factors associated with cesarean section varied among the different BMI groups.

CONCLUSIONS

This study showed no difference in the mean level of AFL between women with different BMIs. Further, high AFL was associated with a higher frequency of cesarean section in all three BMI groups, suggesting that the level of AFL can in the future be used as a predictor of labor outcome among women with labor dystocia despite their BMI.

Effect of pre-operative bicarbonate infusion on maternal and perinatal outcomes among women with obstructed labour in Mbale hospital: A double blind randomized controlled trial

INTRODUCTION

Oral bicarbonate solution is known to improve both maternal and perinatal outcomes among women with abnormal labour (dystocia). Its effectiveness and safety among women with obstructed labour is not known.

OBJECTIVE

To determine the effect and safety of a single-dose preoperative infusion of sodium bicarbonate on maternal and fetal blood lactate and clinical outcomes among women with obstructed labour (OL) in Mbale hospital.

METHODS

We conducted a double blind, randomised controlled trial from July 2018 to September 2019. The participants were women with OL at term (≥37 weeks gestation), carrying a singleton pregnancy with no other obstetric emergency, medical comorbidity or laboratory derangements.

INTERVENTION

A total of 477 women with OL were randomized to receive 50ml of 8.4% sodium bicarbonate (238 women) or 50 mL of 0.9% sodium chloride (239 women). In both the intervention and controls arms, each participant was preoperatively given a single dose intravenous bolus. Every participant received 1.5 L of normal saline in one hour as part of standard preoperative care.

OUTCOME MEASURES

Our primary outcome was the mean difference in maternal venous blood lactate at one hour between the two arms. The secondary outcomes were umbilical cord blood lactate levels at birth, neonatal sepsis and early neonatal death upto 7 days postnatal, as well as the side effects of sodium bicarbonate, primary postpartum hemorrhage, maternal sepsis and mortality at 14 days postpartum.

RESULTS

The median maternal venous lactate was 6.4 (IQR 3.3-12.3) in the intervention and 7.5 (IQR 4.0-15.8) in the control group, with a statistically non-significant median difference of 1.2 mmol/L; p-value = 0.087. Vargha and Delaney effect size was 0.46 (95% CI 0.40-0.51) implying very little if any effect at all.

CONCLUSION

The 4.2g of preoperative intravenous sodium bicarbonate was safe but made little or no difference on blood lactate levels.

TRIAL REGISTRATION

PACTR201805003364421.

Amniotic fluid lactate level as a diagnostic tool for prolonged labour

Prolonged labour can lead to postpartum complications and adverse outcomes for both mother and baby. Measurable parameters can help in the active management of labour, timely diagnosis of dystocia and in the choice of the method of delivery. Progressive uterine contractions are necessary to complete labour successfully. Myometrial fatigue during prolonged labour causes a change from aerobic to anaerobic metabolism, resulting in an accumulation of intramuscular lactic acid and probably a subsequent increase in amniotic fluid lactate concentration. High amniotic fluid lactate level has been associated with ineffective uterine contractions leading to labour arrest. A considerable number of studies conducted so far indicate that the level of lactate in amniotic fluid may be a new non-invasive diagnostic tool for early prediction of prolonged labour and the need for immediate obstetric intervention. Low amniotic fluid lactate level may facilitate a decision to continue vaginal labour by oxytocin augmentation. A high level of amniotic fluid lactate is associated with surgical obstetric procedures. Measuring amniotic fluid lactate level might simplify the patient's allocation to a group, which will benefit from the administration of oxytocin and to a group that will not benefit from further prolongation of labour. This study aimed to briefly review current knowledge on amniotic fluid lactate concentrations measured using standard biochemical methods during the first stage of labour following normal pregnancy, as a possible diagnostic tool for prolonged labour. For this purpose, PubMed, EMBASE, Medline (1990 to July 2020) trials register and reference lists of relevant articles were searched.

Randomized controlled trial of oral bicarbonate treatment for labor stagnation

AIM

The aim of this study was to determine the effect of oral sodium bicarbonate solution on delivery outcome of primiparous women with labor stagnation.

METHODS

This randomized controlled trial study was performed on 142 primiparous pregnant women referred to Jiroft University hospitals who had stagnation during labor. In the intervention group, in addition to oxytocin, 4.26 g of sodium bicarbonate dissolved in 200 mL of water were given orally. The control group received only oxytocin. Data were analyzed by t-test and chi-square test.

RESULTS

The mean interval of dilatation stopping to delivery in the intervention group was significantly lower than the control group (202.34 vs 304.08 min, P = 0.001). The mean duration of the first and second stages of labor in the intervention group was lower than the control group (280.44 vs 397.16 and 35.00 vs 51.72 min respectively, P = 0.001). There was no statistically significant difference between the intervention and control groups in the rate of cesarean section and Apgar score. In the intervention group, the rate of spontaneous delivery was significantly higher (65 vs 56 cases, P = 0.03) than the control group.

CONCLUSION

The results of the present study could suggest the use of oral bicarbonate in stagnation as a cheap and no-cost method to facilitate normal vaginal delivery.

Effect of preoperative bicarbonate infusion on maternal and perinatal outcomes of obstructed labour in Mbale Regional Referral Hospital: a study protocol for a randomised controlled trial

INTRODUCTION

To improve maternal and fetal outcomes among patients with obstructed labour (OL) in low-resource settings, the associated electrolyte and metabolic derangements must be adequately corrected. Oral fluid intake during labour and preoperative intravenous fluid replacement following OL corrects the associated dehydration and electrolyte changes, but it does not completely reverse the metabolic acidosis, that is, a cause of intrapartum birth asphyxia and a risk factor for primary postpartum haemorrhage due to uterine atony. Sodium bicarbonate is a safe, effective, cheap and readily available acid buffer, that is widely used by sportspeople to improve performance. It also appears to improve fetal and maternal outcomes in abnormally progressing labour. However, its effects on maternal and fetal outcomes among patients with OL is unknown. We aim at establishing the effect of a single-dose preoperative infusion of sodium bicarbonate on maternal and fetal lactate levels and clinical outcomes among patients with OL.

METHODS AND ANALYSIS

This will be a double blind, randomised controlled clinical phase IIb trial. We will randomise 478 patients with OL to receive either 50 mL of placebo with standard preoperative infusion of normal saline (1.5 L) or 4.2 g of sodium bicarbonate solution (50 mL of 50 mmol/L) with the preoperative infusion of normal saline (1.5 L). The primary outcome will be mean lactate levels in maternal capillary blood at 1 hour after study drug administration and in the arterial cord blood at birth. We will use the intention-to-treat analysis approach. Secondary outcomes will include safety, maternal and fetal morbidity and mortality up to 14 days postpartum.

ETHICS AND DISSEMINATION

Makerere University School of Medicine Research and Ethics Committee and Uganda National Council for Science and Technology have approved the protocol. Each participant will give informed consent at enrollment.

TRIAL REGISTRATION NUMBER

PACTR201805003364421.

The Myometrium: From Excitation to Contractions and Labour

We start by describing the functions of the uterus, its structure, both gross and fine, innervation and blood supply. It is interesting to note the diversity of the female's reproductive tract between species and to remember it when working with different animal models. Myocytes are the overwhelming cell type of the uterus (>95%) and our focus. Their function is to contract, and they have an intrinsic pacemaker and rhythmicity, which is modified by hormones, stretch, paracrine factors and the extracellular environment. We discuss evidence or not for pacemaker cells in the uterus. We also describe the sarcoplasmic reticulum (SR) in some detail, as it is relevant to calcium signalling and excitability. Ion channels, including store-operated ones, their contributions to excitability and action potentials, are covered. The main pathway to excitation is from depolarisation opening voltage-gated Ca²⁺ channels. Much of what happens downstream of excitability is common to other smooth muscles, with force depending upon the balance of myosin light kinase and phosphatase. Mechanisms of maintaining Ca²⁺ balance within the myocytes are discussed. Metabolism, and how it is intertwined with activity, blood flow and pH, is covered. Growth of the myometrium and changes in contractile proteins with pregnancy and parturition are also detailed. We finish with a description of uterine activity and why it is important, covering progression to labour as well as preterm and dysfunctional labours. We conclude by highlighting progress made and where further efforts are required.

Effects of Increased Frequency, High Dose, and Pulsatile Oxytocin Regimens on Abnormal Labor Delivery

Background

The current guideline for oxytocin regimens in the abnormal labor of delivery is continuous infusion. The objective of the present study was to compare effects and safety measures of various available regimens of oxytocin in abnormal labor delivery.

Material/Methods

In this clinical experimental study, a total of 900 pregnant women admitted for delivery were randomized into 5 group with 162 each. Pregnant women received oxytocin as continuous administration of 16 mU/min (Group I), 1 mU/min (group II), 4 mU/min (group III), 5 mU/min quarter-hourly (group IV), and through a syringe pump (group V). Measurement of the expense of delivery, the ratio of the instrumental delivery, and the other secondary outcome measures was performed to find the best regimen of oxytocin. The 2-tailed paired t test and Mann-Whitney U test following Dunnett’s multiple comparison tests were used at 95% confidence level.

Results

Pulsatile delivery had least risk of instrumental delivery as compared to continuous infusion (p<0.0001, q=6.663) and normal-frequency low-dose (p<0.0001, q=5.638) of oxytocin. The time required from infusion to delivery was longer for group II (p=0.001, q=2.925), group IV (p<0.0001, q=4.829), and group V (p<0.0001, q=41.456) than for group I. The expense of delivery was: group I < group II < group IV < group III < group V.

Conclusions

High-dose and pulsatile preparation of oxytocin had reduced risks of operative delivery vs. continuous administration.