Tocolysis: A Review of the Literature

Phenanthroline relaxes uterine contractions induced by diverse contractile agents by decreasing cytosolic calcium concentration

Uterine contractions during labor and preterm labor are influenced by a complex interplay of factors, including hormones and inflammatory mediators. This complexity may contribute to the limited efficacy of current tocolytics for preterm labor, a significant challenge in obstetrics with 15 million cases annually and approximately 1 million resulting deaths worldwide. We have previously shown that the myometrium expresses bitter taste receptors (TAS2Rs) and that their activation leads to uterine relaxation. Here, we investigated whether the selective TAS2R5 agonist phenanthroline can induce relaxation across a spectrum of human uterine contractions and whether the underlying mechanism involves changes in intracellular Ca2+ signaling. We performed experiments using samples from pregnant women undergoing scheduled cesarean delivery, assessing responses to various inflammatory mediators and oxytocin with and without phenanthroline. Our results showed that phenanthroline concentration-dependently inhibited contractions induced by PGF2α, U46619, 5-HT, endothelin-1 and oxytocin. Furthermore, in hTERT-infected human myometrial cells exposed to uterotonics, phenanthroline effectively suppressed the increase in intracellular Ca2+ concentration induced by PGF2α, U46619, oxytocin, and endothelin-1. These results suggest that the selective TAS2R5 agonist may not only significantly reduce uterine contractions but also decrease intracellular Ca2+ levels. This study highlights the potential development of TAS2R5 agonists as a new class of uterine relaxants, providing a novel avenue for improving the management of preterm labor.

Association of Antenatal Terbutaline and Respiratory Support Requirements in Preterm Neonates

BACKGROUND

Before the advent of antenatal steroids, early non-invasive respiratory support (NIV), and intratracheal surfactant, antenatal terbutaline was also used to improve lung compliance and reduce the incidence of respiratory distress syndrome (RDS).

OBJECTIVES

The objective of this paper was to study the association between antenatal terbutaline and endotracheal intubation (ET) within the first 24 hours of life, RDS, bronchopulmonary dysplasia (BPD), and intraventricular hemorrhage (IVH) in infants with the gestational age (GA) of <32 weeks, and to study the association between antenatal terbutaline, and ET or NIV within the first 24 hours of life, and RDS in infants with the GA of 32 to 36 weeks.

METHOD

This was a retrospective medical record review of preterm infants delivered at a single tertiary care center from October 2016 to December 2020. Multivariable logistic regression was used to explore the association between antenatal terbutaline and neonatal respiratory support.

RESULT

1,794 infants were included, 234 (13.0%) had the GA of <32 weeks and 1,560 (86.9%) had the GA of 32 to 36 weeks. Antenatal terbutaline, corticosteroid, or both agents were administered in 561 (31.3%), 1,461 (81.4%), and 555 (30.9%), respectively. Antenatal terbutaline was significantly associated with a reduction in ET (adjusted odds ratio [aOR] = 0.40, 95% confident interval [CI] 0.19-0.82, p = 0.012) in infants with the GA of <32 weeks, but not in infants with the GA of 32-36 weeks. Antenatal terbutaline was not associated with RDS or BPD but was significantly associated with a reduction in grade III-IV IVH (aOR 0.11, CI 0.01-0.98; p = 0.048), in infants with the GA of <32 weeks.

CONCLUSION

In a state-of-the-art neonatal care setting, antenatal terbutaline was associated with a reduction in ET during the first 24 hours in infants with the GA of <32 weeks. The use of antenatal terbutaline to improve acute neonatal respiratory outcomes merits reconsideration.

KEY POINTS

· The neonatal respiratory benefits of antenatal terbutaline in the era of antenatal corticosteroids were uncertain.. · Terbutaline is associated with a reduction in endotracheal intubation in a modern care setting.. · The role of terbutaline, and potentially other betamimetics, to improve neonatal respiratory outcomes merits reconsideration..

Trends in neonatal morbidity and mortality for very low birthweight infants: a 20-year single-center experience

OBJECTIVE

To describe trends in mortality and morbidity rates of very low birth weight infants as well as their pre-, peri- and postnatal characteristics over a period of 20 years' time.

METHODS

Retrospective study in all very low birth weight infants admitted to the neonatal intensive care unit of the University Hospitals Ghent from 1 January 2000, to 31 December 2020. Mortality was the primary outcome variable with major morbidities being co-primary outcome variables. Pre-, peri- and postnatal characteristics are secondary outcome variables. We compared pre-, peri- and postnatal characteristics, as well as major morbidities between different groups with comparable rates of mortality.

RESULTS

We included a total of 2037 very low birth weight infants and divided them in 3 epochs based on stepwise reductions in mortality in 2008 and 2013: 2000-2007 (n = 718), 2008-2012 (n = 506) and 2013-2020 (n = 813). Mortality decreased significantly over the years in all gestational ages, but predominantly in those with the youngest gestational age. Changes in obstetric and neonatal care were observed over time. Most significant changes were the increased use of antenatal corticosteroids, magnesium sulfate and surfactant. Intraventricular hemorrhage grade III/IV decreased significantly in all gestational ages. Significant increase in retinopathy of prematurity was observed. Bronchopulmonary dysplasia at 36 weeks and discharge home with oxygen is increasing in the total group. In those born below 26 weeks a slight increase in all major morbidities was observed especially of patent ductus arteriosus and retinopathy of prematurity. Increase of all other major morbidities seems to stabilize in epoch 3. The number of infants surviving without any major morbidity increases to almost 1/2 in all very low birth weight infants and to 1/10 in those born 24-25 weeks gestation.

CONCLUSION

Analysis of the real-life experience showed that survival in very low birth weight infants significantly increased over time. Evolution of major morbidities will have to be carefully watched in the future.

Nanomedicine strategies to improve therapeutic agents for the prevention and treatment of preterm birth and future directions

The World Health Organisation (WHO) estimates 15 million babies worldwide are born preterm each year, with 1 million infant mortalities and long-term morbidity in survivors. Whilst the past 40 years have provided some understanding in the causes of preterm birth, along with development of a range of therapeutic options, notably prophylactic use of progesterone or uterine contraction suppressants (tocolytics), the number of preterm births continues to rise. Existing therapeutics used to control uterine contractions are restricted in their clinical use due to pharmacological drawbacks such as poor potency, transfer of drugs to the fetus across the placenta and maternal side effects from activity in other maternal systems. This review focuses on addressing the urgent need for the development of alternative therapeutic systems with improved efficacy and safety for the treatment of preterm birth. We discuss the application of nanomedicine as a viable opportunity to engineer pre-existing tocolytic agents and progestogens into nanoformulations, to improve their efficacy and address current drawbacks to their use. We review different nanomedicines including liposomes, lipid-based carriers, polymers and nanosuspensions highlighting where possible, where these technologies have already been exploited e.g. liposomes, and their significance in improving the properties of pre-existing therapeutic agents within the field of obstetrics. We also highlight where active pharmaceutical agents (APIs) with tocolytic properties have been used for other clinical indications and how these could inform the design of future therapeutics or be repurposed to diversify their application such as for use in preterm birth. Finally we outline and discuss the future challenges.

Tocolytic Therapy Inhibiting Preterm Birth in High-Risk Populations: A Systematic Review and Meta-Analysis

This systematic review aimed to identify the benefits and possible harms of tocolytic therapy for preterm labour management in the context of pregnant women with extremely preterm birth, multiple gestations, or growth-restricted foetuses. A comprehensive search using MEDLINE, Embase, the Cochrane Central Register of Controlled Trials, CINAHL, and the WHO Global Index Medicus databases was conducted from 10 to 15 July 2021. We included randomized controlled trials and non-randomized studies that assessed the effects of tocolysis compared with placebo or no treatment. We found 744 reports and, finally, nine studies (three randomized controlled trials and six cohort studies) pertaining to women with <28 weeks of gestation were included. No eligible studies were identified among women with a multiple pregnancy or a growth-restricted foetus. A meta-analysis of the trial data showed that there were no clear differences in perinatal death nor for a delay in birth. Non-randomized evidence showed that tocolysis delayed birth by 7 days, though there was no clear difference for preterm birth. In summary, it remains unclear whether tocolytic therapy for inhibiting preterm labour is beneficial for these subgroups of women and their newborns. Further well-designed randomized controlled trials and observational studies are needed to address the lack of evidence regarding tocolytic agents in these populations.

Adjunct Therapy at Time of Examination-Indicated Cervical Cerclage in Singleton Pregnancies: A Systematic Review and Meta-analysis

OBJECTIVE

Physical examination-indicated cerclage for cervical insufficiency prolongs gestation, but evidence on the addition of adjuncts to further prolong latency is limited. The aim of this systematic review and meta-analysis was to compare gestational latency between those who did and did not receive adjunct antibiotic or tocolytic therapy at the time of examination-indicated cerclage.

STUDY DESIGN

Electronic databases (1966-2020) were searched for randomized controlled trials (RCTs) and cohort studies comparing adjunct antibiotic or tocolytic use versus nonuse at time of examination-indicated cerclage, defined as placement for cervical dilation ≥1 cm, in a current singleton pregnancy. Studies including individuals with intra-amniotic infection, cerclage in place, nonviable gestation, or ruptured membranes were excluded. The primary outcome was latency from cerclage placement to delivery. Secondary outcomes included preterm birth, preterm premature rupture of membranes, birth weight, and neonatal survival. Risk of bias was assessed using standardized tools. Heterogeneity was assessed using χ 2 and I 2 tests. Results were pooled and analyzed using a random-effects model. This study is registered with The International Prospective Register of Systematic Reviews (PROSPERO) with registration no.: CRD42021216370.

RESULTS

Of 923 unique records, 163 were reviewed in full. Three met inclusion criteria: one RCT and two retrospective cohorts. The included RCT (n = 50) and one cohort (n = 142) compared outcomes with and without adjunct use of antibiotic and tocolytic, while the second cohort (n = 150) compared outcomes with and without adjunct tocolytic, with a subpopulation also receiving antibiotics. The RCT was nested within one of the cohorts, and therefore only one of these two studies was utilized for any given outcome to eliminate counting individuals twice. Risk of bias was "critical" for one cohort study, "moderate" for the other cohort study, and "some concerns" for the RCT. Gestational latency could not be pooled and meta-analyzed. Adjunct tocolytic-antibiotic therapy was not associated with a decrease in risk of preterm delivery <28 weeks (relative risk [RR] = 0.90, 95% confidence interval [CI]: 0.65-1.26; χ 2 = 0.0, I 2 = 0.0%) or neonatal survival to discharge (RR = 1.11, 95% CI: 0.91-1.35; χ 2 = 0.05, I 2 = 0.0%).

CONCLUSION

There is not enough evidence to robustly evaluate the use of adjunct tocolytics or antibiotics at time of examination-indicated cerclage to prolong latency.

KEY POINTS

· Limited data on adjunct antibiotic tocolytics at cerclage.. · Widely variable practices at time of cerclage identified.. · Role of adjunct therapies at time of examination-indicated cerclage remains unclear..

Chinese Herbal Medicines Have Potentially Beneficial Effects on the Perinatal Outcomes of Pregnant Women

Introduction: Tocolytic treatment is beneficial to pregnant women with a risk of premature labor or miscarriage. However, previous reports have shown that progestogen might not be effective and ritodrine may increase the risk of maternal vascular-related diseases. Chinese herbal products (CHP) are used as alternative therapies for pregnant women. The goal was to evaluate the efficacy of combined tocolytic therapy and CHP therapy in pregnancy outcomes for pregnant women in Taiwan.

Materials and Methods: We conducted a retrospective cohort study based on the National Health Insurance Research Database. A total of 47,153 pregnant women treated with tocolytics aged 18–50 years from 2001 to 2015 were selected from two million random samples. According to the medical use of tocolytics and CHP, we divided the users into two groups: western medicine (WM) only (n = 40,961) and WM/CHP (n = 6,192) groups. A propensity score (PS)-matched cohort (6,192 pairs) was established based on baseline confounders. All participants were followed up to perinatal outcomes. Conditional logistic regression analysis was used to examine the effects of CHP use on the odds of miscarriage and preterm birth.

Results: The adjusted odds ratio (OR) for premature birth in the WM/CHP group (n = 411, 6.64%) was significantly lower than in the WM group (n = 471, 7,61%) (0,86, 95% confidence interval [CI], 0.74–0.99). Further subgroup analysis based on the usage of formulae that activate blood and remove stasis or purgative formulae, the adjusted OR of preterm birth of those using these formulae was significantly lower in the WM/CHP group (n = 215, 6.32%) than that in the WM group (n = 265, 7.77%) (OR: 0.79, 95% CI: 0.65–0.96).

Conclusion: We found that the combination of CHP and tocolytics can be beneficial to pregnant women in the prevention of premature birth. Further research is required to investigate causal relationships.

Tocolytic Treatment for the Prevention of Preterm Birth from a Taiwanese Perspective: A Survey of Taiwanese Obstetric Specialists

Preterm birth represents a great burden to the healthcare system, resulting in the consideration for the use of tocolytic therapy to provide a "better time" for delivery in order to buy time to accelerate fetal lung maturity, thereby minimizing prematurity-related morbidity and mortality. However, the benefits and potential side effects and risks of tocolytic treatment for preterm birth should be carefully balanced. Although many countries and societies provide guidelines or consensuses for the management for preterm birth, there is no standardized national guideline or consensus in Taiwan. As such, great heterogeneity is suspected in preterm labor management, contributing to the uncertainty of attitudes and practice patterns of obstetric specialists in Taiwan. This study attempts to understand the attitudes and practice patterns regarding tocolytic therapy in Taiwan. A paper-based survey was conducted at the 2020 Taiwan Society of Perinatology Conference on 8 December 2020, exploring how obstetric specialists would use tocolytics under nine different clinical scenarios, such as a short cervix, preterm labor, maintenance tocolysis, preterm premature rupture of membranes, etc. Three hundred ten specialists attended the conference, and 77 responded to the survey with a response rate of 24.8%. According to the survey, many of these specialists would prescribe tocolytics for less evidence-based indications, including 22% for abdominal tightness, 46% for a short cervix, 60% for maintenance tocolysis, and 89% for repeat tocolysis, with the preferred first line medication being ritodrine and nifedipine. We concluded that tocolysis is widely accepted and practiced in Taiwan. More research is needed to include Taiwan-specific economic and cultural factors as well as associated adverse effects and patients' outcomes.

Evaluation of the Fetal Therapy Evidence in Lower Urinary Tract Obstruction: Would an ERAS Guideline Improve Outcomes?

BACKGROUND

Pregnancies that are prenatally identified to have fetal anomalies are complex and require expert multidisciplinary care. As many conditions can impact the fetus prenatally and require intervention, an enhanced recovery after surgery (ERAS) for lower urinary tract obstruction (LUTO) is being evaluated to determine the level of evidenced-based data available.

PROBLEM

The percutaneous ultrasound-guided fetal surgery procedure for bladder neck obstruction is the focus for elements of preoperative counseling, intraoperative procedure/risk complications, and postoperative management.

METHODS

A quality improvement review Squire 2.0 (2000-2020) was undertaken for the percutaneous LUTO fetal surgery shunting (lower urinary tract obstruction), process and procedure which require 2 process pathways, one to evaluate the fetal candidate and a second to treat. This structured review is focused on identifying the process elements to allow the determination of the number of evidenced-based elements that would allow for audit and measurement of the clinical element variance for comparative feedback to the individual surgical provider or surgery center.

INTERVENTIONS

Titles and abstracts were screened to identify potentially relevant articles with priority given to meta-analyses, systematic reviews, randomized controlled studies, nonrandomized controlled studies, reviews, and case series.

RESULTS

A series of potential clinical elements for the diagnostic fetal evaluation and for the 3 protocol areas of surgical care for the procedures (pre-, intra-, and postoperative care) are identified using an ERAS-like process.

CONCLUSIONS

The identified clinical elements have the potential for ERAS-LUTO fetal therapy guideline. Multidisciplinary collaboration (surgeon, anesthesia, nursing, imaging, and laboratory) is required for ERAS quality improvement in the pre-, intra-, and postoperative processes. Process elements in each of the operative areas can be audited, evaluated, compared, and modified/improved.

Preterm Labor and Birth: A Clinical Review

When caring for women experiencing preterm labor and birth, nurses play a significant role as bedside experts, advocates, patient educators, and key members of the maternity care team. Enhanced expertise on clinical and professional knowledge of preterm labor and birth is crucial in prevention and treatment. As preterm birth rates continue to rise, perinatal nurses as well-informed clinical experts have the opportunity to offer innovative education, holistic assessments, and communication through shared decision-making models. Educating pregnant women about early recognition of preterm labor warning signs and symptoms allows for timely diagnosis, interventions, and treatment. Informed and collaborative nursing practice improves quality of clinical care based on individualized interactions. A clinical review of preterm labor and preterm birth is presented for perinatal nurses.

Tocolytic effect of the monoterpenic phenol isomer, carvacrol, on the pregnant rat uterus

Despite the wide application of carvacrol (CAR) in different biological and medical areas, there is still insufficient electrophysiological data on the mechanisms of action of CAR, particularly in the pregnant uterine function. The aim of this study was to evaluate the in vitro tocolytic effect of CAR on the contractility of isolated pregnant rat uterus in the presence of a calcium channel antagonist (nifedipine) and a cyclooxygenase inhibitor (indomethacin). The uteri were isolated from pregnant Wistar rats at 16-18 days of pregnancy and suspended in an isolated organ bath chamber containing a Ringer's physiological solution and aerated with 95% O₂and 5% CO₂. Samples were used in functional tests to evaluate the inhibitory effect of CAR at increasing concentrations on the rhythmic spontaneous, oxytocin-induced phasic, K⁺-induced tonic, and Ca²⁺-induced contractions. The differences in inhibitory concentration-50 and E_maxamong the compounds were determined using the one-way ANOVA followed by a post hoc Student-Newman-Keuls or Bonferroni test, in all casesP < 0.05 was considered statistically significant. Nifedipine was used as positive controls where required. CAR caused a significant concentration-dependent inhibition of the uterine contractions induced by the pharmaco- and electro-mechanic stimuli. We showed that the inhibitory effects of CAR depends on the type of muscle contraction stimuli, and that it acts stronger in spontaneous rhythmic activity and in contractions of isolated rat uterus induced by Ca²⁺. Nifedipine was more potent than CAR and indomethacin on the uterine contractility (P < 0.05), but none of them was more effective than nifedipine. Therefore, the tocolytic effect induced by CAR was associated with the blockade of the calcium channels in the pregnant rat uterus. This property placed CAR as a potentially safe and effective adjuvant agent in cases of preterm labor, an area of pharmacological treatment that requires urgent improvement.

Dysregulation of bile acids increases the risk for preterm birth in pregnant women

Preterm birth (PTB) is the leading cause of perinatal mortality and newborn complications. Bile acids are recognized as signaling molecules regulating a myriad of cellular and metabolic activities but have not been etiologically linked to PTB. In this study, a hospital-based cohort study with 36,755 pregnant women is conducted. We find that serum total bile acid levels directly correlate with the PTB rates regardless of the characteristics of the subjects and etiologies of liver disorders. Consistent with the findings from pregnant women, PTB is successfully reproduced in mice with liver injuries and dysregulated bile acids. More importantly, bile acids dose-dependently induce PTB with minimal hepatotoxicity. Furthermore, restoring bile acid homeostasis by farnesoid X receptor activation markedly reduces PTB and dramatically improves newborn survival rates. The findings thus establish an etiologic link between bile acids and PTB, and open an avenue for developing etiology-based therapies to prevent or delay PTB.

The diagnostic value of fetal fibronectin testing in clinical practice

AIM

To evaluate the clinical management to withhold treatment for preterm labor in symptomatic women with an intermediate cervical length and negative fetal fibronectin (fFN) testing.

METHODS

A retrospective cohort study was performed in a tertiary care teaching hospital in the Netherlands. Pregnant women with a gestational age between 23⁺⁵ to 34⁺⁰ weeks, with the presence of regular uterine contractions accompanied by a cervical length between 15 and 30 mm and intact membranes, who underwent fFN testing were included to obtain the diagnostic value of fFN testing for preterm delivery within 7 days.

RESULTS

Fetal fibronectin testing has an extremely high negative predictive value (100%) and sensitivity (100%) for delivery within 7 days, in singleton and multiple pregnancies. However, specificity (64%) and positive predictive value (10%) of fFN testing in singleton pregnancies are low. Blood present on the fFN sample does not affect the reliability of the fFN test; the negative predictive value remains 100%.

CONCLUSION

Women with symptoms of early preterm labor, intact membranes, a cervical length between 15 and 30 mm and negative fFN testing do not deliver within 7 days. Administration of corticosteroids and tocolytics can safely be withhold. Furthermore, blood on the fFN sample does not change the reliability of the fFN test.

Periviability: A Review of Key Concepts and Management for Perinatal Nursing

One of the most complex clinical problems in obstetrics and neonatology is caring for pregnant women at the threshold of viability. Births near viability boundaries are grave events that carry a high prevalence of neonatal death or an increased potential for severe lifelong complications and disabilities among those who survive. Compared with several decades ago, premature infants receiving neonatal care by today's standards have better outcomes than those born in other eras. However, preterm labor at periviability represents a more complex counseling and management challenge. Although preterm birth incidence between 20/7 and 25/7 weeks has remained unchanged, survival rates at earlier gestational ages have increased as perinatal and neonatal specialties have become more adept at caring for this at-risk population. Women face difficult choices about obstetric and neonatal interventions in light of uncertainties around survival and outcomes. This article reviews current neonatal statistics in reference to short- and long-term outcomes, key concepts in obstetric clinical management of an anticipated periviable birth, and counseling guidance to ensure shared-decision making.

Maintenance tocolysis: a reappraisal of clinical evidence

INTRODUCTION

Maintenance tocolysis, mostly defined as the continuation of tocolytic treatment beyond 48 h, remains a matter of debate. There is no sufficient evidence from randomized controlled trials, that maintenance tocolysis is able to prolong pregnancy significantly and to reduce severe neonatal morbidity and mortality. Hence, it is not recommended in current guidelines. On the contrary, maintenance tocolysis is commonly used in clinical practice and subject of current clinical-scientific investigations.

TOCOLYTICS FOR MAINTENANCE TREATMENT

None of the conventional tocolytics (beta-sympathomimetics, calcium-channel blockers, magnesium, cyclooxygenase inhibitors, and oxytocin receptor antagonists) have proven to be appropriate for maintenance treatment. Progesterone and 17-α-hydroxyprogesterone caproate have shown promising results in low-quality randomized trials, but not in high-quality studies.

DISCUSSION

Basically, the value of studies regarding maintenance tocolysis is limited by a considerable heterogeneity, its mostly low quality, significant differences in methodology as well as the inadequate statistical power due to the small number of women studied. So far, maintenance tocolysis is a case-by-case decision outweighing the benefits and harms of tocolytic treatment.