Magnesium Sulfate for Preterm Labor and Preterm Birth

Monitoring of inflammatory preterm responses via myometrial cell based multimodal electrophysiological and optical biosensing platform

Preterm birth (PTB) remains a leading cause of neonatal morbidity and mortality, with inflammation-induced PTB posing a significant challenge due to its complex pathophysiology. To address this, we developed an in vitro platform utilizing hTERT-immortalized human myometrial (hTERT-HM) cells integrated with a multielectrode array (MEA) biosensing system and optical calcium imaging. Compared to primary uterine myometrial cells, hTERT-HM cells exhibit superior reproducibility, high scalability, and convenient manipulation, facilitating the consistent and large-scale investigations. This advanced system facilitates simultaneous real-time monitoring of electrophysiological activity and intracellular calcium transient, providing detailed insights into uterine cell behavior during inflammatory PTB. Our study revealed that oxytocin (OT) induces regular contractions in hTERT-HM cells, and the synergistic effect of OT and lipopolysaccharide (LPS) disrupts electrophysiological patterns and calcium signaling, closely mimicking the pathophysiology of inflammation-induced PTB. Meanwhile, magnesium sulfate is validated to effectively suppress OT-induced calcium release and mitigate LPS-triggered irregular electrophysiological signals. By integrating advanced biosensing technologies and advantages of hTERT-HM cells, this platform offers a reliable, reproducible model to investigate the mechanisms of inflammation-driven PTB and further develop targeted therapeutic interventions.

Comparative effectiveness and safety of nifedipine and magnesium sulfate as treatment options for preterm birth: a systematic review and meta-analysis

OBJECTIVES

Preterm birth (PTB) is a major cause of neonatal morbidity and mortality worldwide. Effective use of tocolytic agents may improve perinatal outcomes. This study aims to compare the effectiveness and safety of nifedipine and magnesium sulfate in the treatment of PTB.

DESIGN

A systematic review and meta-analysis.

DATA SOURCES

China National Knowledge Infrastructure, China Science and Technology Journal Database, WanFang, PubMed, Embase, Web of Science and Cochrane were searched from inception to 1 December 2024.

ELIGIBILITY CRITERIA

We included randomised controlled trials (RCTs) and cohort studies that compare the efficacy and safety of magnesium sulfate versus nifedipine in treating PTB.

DATA EXTRACTION AND SYNTHESIS

Two researchers independently screened studies and extracted data. Risk of bias was assessed using the Cochrane risk-of-bias assessment tool for RCTs and the modified Newcastle-Ottawa Scale for non-randomised studies. Meta-analysis was conducted using Review Manager V.5.4.

RESULTS

In all, 50 articles were included in this review, comprising 6072 cases (n=3014 for the magnesium sulfate group; n=3058 for the nifedipine group). Compared with the magnesium sulfate group, the nifedipine group was more favourable in terms of time to onset of action and prolongation of days of gestation, as well as higher neonatal 1 min Apgar scores. The use of magnesium sulfate was associated with a higher incidence of maternal side effects, specifically tachycardia, flushing, palpitations, dizziness and nausea. In addition, the magnesium sulfate group also showed a higher incidence of neonatal respiratory distress syndrome than the nifedipine group.

CONCLUSION

Compared with magnesium sulfate, nifedipine is more effective with a faster onset of action and a longer prolonging pregnancy. Additionally, nifedipine may be safer for fewer maternal side effects and better neonatal outcomes. Further studies are needed to confirm the long-term safety and efficacy of these treatments.

Uterine first-pass effect: Unlocking the potential of vaginally administered ritodrine-loaded thermosensitive gel for uterine drug delivery

Preterm birth (PTB) remains a leading cause of infant mortality and morbidity, significantly affecting the long-term health, welfare, and development of newborns. Tocolytics, such as ritodrine, a β2-adrenergic receptor agonist, are widely used in developing countries due to their affordability for preventing PTB by inhibiting uterine contractions. However, ritodrine's short half-life necessitates frequent administration, and prolonged high-dose usage often leads to serious maternal side effects, prompting discontinuation. The uterine first-pass effect, where vaginally administered drugs preferentially target the uterus, can enhance drug concentration in uterine tissue while minimizing systemic absorption and side effects. This study designed a kind of ritodrine-loaded thermosensitive gel (Gel@Rit) to intervene in PTB by exploiting the uterine first-pass effect and investigate its underlying mechanisms. The gel, formulated with poloxamer, demonstrated excellent temperature sensitivity and viscosity, ensuring sustained ritodrine release in vitro. Plasma pharmacokinetic and tissue distribution studies in pregnant mice confirmed the uterine first-pass effect, showing significantly higher drug concentrations in the uterus and markedly lower plasma levels following Gel@Rit administration. The distinctive drug-time curve in Gel@Rit-treated mice, along with uterine tissue fluorescence profiles, elucidated four mechanisms of uterine localization: diffusion through reproductive tract cavities, penetration via vaginal and uterine structures, diffusion through systemic circulation, and retrograde transvaginal veno-uterine artery exchange. This study provides valuable insights into vaginal drug delivery research methodologies, advancing therapeutic strategies for uterine-related conditions and benefiting clinical outcomes in PTB prevention.

Vaginal Progesterone for Pregnancy Prolongation After Arrested Preterm Labor: A Randomized Clinical Trial

Importance

Women with arrested preterm labor (APTL) are at very high risk for spontaneous preterm delivery (SPTD), the leading cause of neonatal mortality and morbidity. To date, no maintenance therapy has been found to be effective for pregnancy prolongation. A few clinical trials with considerable methodological limitations have demonstrated some efficacy for 400 mg vaginal micronized progesterone (VMP) in women with APTL.

Objective

To investigate the effectiveness of daily 400 mg VMP for the prolongation of pregnancy after APTL.

Design, Setting, and Participants

This randomized clinical trial was conducted between December 19, 2018, and February 27, 2023, in 3 university-affiliated medical centers in Israel. Participants included women with singleton and twin pregnancies after APTL following tocolysis at 24 weeks 0 days to 34 weeks 0 days' gestation. Women with a history of preterm delivery or asymptomatic cervical shortening in the current pregnancy were excluded.

Interventions

Participants were randomly allocated to receive VMP 200 mg twice a day or no treatment until 36 weeks 6 days' gestation.

Main Outcomes and Measures

The primary end points were mean number of days from study enrollment to delivery and the rate of SPTD prior to 37 weeks' gestation.

Results

A total of 129 participants were enrolled (65 in the VMP group and 64 in the no-treatment group). Mean (SD) age was 27.6 (5.1) years. Between the VMP and no-treatment groups, there was no difference in pregnancy prolongation (mean [SD], 40.0 [17.8] vs 37.4 [20.3] days; P = .44) and the rate of SPTD (16 [25%] vs 19 [30%]; relative risk, 0.8; 95% CI, 0.5-1.5; P = .52). In twin pregnancies, including 12 and 15 pairs in the VMP and no-treatment groups, respectively, VMP prolonged pregnancy (mean [SD], 43.7 [18.1] vs 26.1 [15.2] days; P = .02), postponed the delivery week (36.5 [1.4] vs 34.7 [2.2] weeks; P = .01), shortened the length of stay in the neonatal intensive care unit (4.9 [10.6] vs 13.2 [18.5] days; P = .03) and overall hospital stay (8.3 [9.6] vs 15.1 [17.2] days; P = .03), and was associated with a higher birth weight (2444 [528] vs 2018 [430] g; P = .01).

Conclusions and Relevance

These findings show that VMP given in a dosage of 200 mg twice a day following APTL is not an effective treatment to prolong pregnancy or prevent SPTD. However, VMP demonstrated beneficial effects in twin pregnancies, warranting further investigation.

Trial Registration

ClinicalTrials.gov Identifier: NCT02430233.

Preventing Preterm Birth: Exploring Innovative Solutions

This review examines the complexities of preterm birth (PTB), emphasizes the pivotal role of inflammation in the pathogenesis of preterm labor, and assesses current available interventions. Antibiotics, progesterone analogs, mechanical approaches, nonsteroidal anti-inflammatory drugs, and nutritional supplementation demonstrate a limited efficacy. Tocolytic agents, targeting uterine activity and contractility, inadequately prevent PTB by neglecting to act on uteroplacental inflammation. Emerging therapies targeting toll-like receptors, chemokines, and interleukin receptors exhibit promise in mitigating inflammation and preventing PTB.

Maternal urinary metal(loid)s and risk of preterm birth: A cohort study in the Tibetan Plateau

Maternal metal(loid)s exposure has been related to preterm birth (PTB), but the results are still inconclusive. Previous studies have mainly discussed the harmful metal(loid)s, neglecting beneficial ones. We examined the association of maternal metal(loid)s with PTB and gestational age (GA) in a birth cohort from the Tibetan Plateau. We measured 29 metal(loid)s in urine samples from 1081 pregnant women in the third trimester. Information regarding demographics, socioeconomic status, diet, medication, and lifestyle was collected through standardized interviews. The associations of single metal(loid)s with PTB or GA were evaluated using a generalized linear mixed-effects model or linear mixed-effects model. Elastic net and Bayesian kernel machine regressions were used to explore the joint associations. Magnesium (Mg), Copper (Cu), and Tin (Sn) were the main "harmful" metal(loid)s positively and negatively associated with PTB or GA, respectively. Mg was the dominant "harmful" metal(loid)s associated with PTB in a J-shape. A one-fold increase in Mg was associated with a 38% increased risk of PTB [OR (95% CI) = 1.38 (1.15, 1.65), PFDR＜0.05] and 0.17 weeks shortening of GA [β (95% CI) = -0.25 (-0.35, -0.14), PFDR＜0.05]. Cesium (Cs), rubidium (Rb), and Molybdenum (Mo) were the main "beneficial" metals. Cs dominated the "beneficial" associations and was negatively associated with PTB in a linear manner. A one-fold increase in Cs was associated with a 67% decreased risk of PTB [OR (95% CI) = 0.43 (0.27, 0.67), PFDR＜0.05] and 0.24 weeks of prolonged GA [β (95% CI) = 0.35 (0.13, 0.56), PFDR＜0.05]. Ethnicity and living altitude modified the association of Mg and Cu with PTB or GA. In conclusion, Maternal urinary metal(loid)s were bi-directionally associated with PTB in a population in the Tibetan Plateau. Mg and Cs were the dominant "harmful" and "beneficial" metal(loid)s, respectively.

Sow Nutrition, Uterine Contractions, and Placental Blood Flow during the Peri-Partum Period and Short-Term Effects on Offspring: A Review

The birth process is a crucial event for piglet survival. Along with increasing litter sizes, not only has the duration of parturition increased, but placental blood flow per piglet has reduced and placental area per piglet has become smaller, making these piglets more susceptible for hypoxia. Diminishing the risk of piglet hypoxia by either reducing the total duration of parturition or increasing fetal oxygenation may reduce the incidence of stillbirth and early post-partum mortality. This review discusses options to do so by nutritionally supporting the sow in the final pre-partum period, after discussing the role of uterine contractions and placental blood flow. Providing sufficient energy seems to be a logical first step, but also other nutrients needed for uterine contractions, such as calcium, or enhancing uterine blood flow by using nitrate seem promising. These nutrient requirements may depend on litter size.

Postpartum Respiratory Depression

Postpartum respiratory depression is a complex, multifactorial issue that encompasses a patient's baseline preexisting conditions, certain pregnancy-specific conditions or complications, as well as the iatrogenic element of various medications given in the peripartum period. In this review, we discuss many of these factors including obesity, sleep-disordered breathing, chronic lung disease, neuromuscular disorders, opioids, preeclampsia, peripartum cardiomyopathy, postpartum hemorrhage, amniotic fluid embolism, sepsis, acute respiratory distress syndrome (ARDS), and medications such as analgesics, sedatives, anesthetics, and magnesium. Current recommendations for screening, treatment, and prevention are also discussed.

Landscape of Preterm Birth Therapeutics and a Path Forward

Preterm birth (PTB) remains the leading cause of infant morbidity and mortality. Despite 50 years of research, therapeutic options are limited and many lack clear efficacy. Tocolytic agents are drugs that briefly delay PTB, typically to allow antenatal corticosteroid administration for accelerating fetal lung maturity or to transfer patients to high-level care facilities. Globally, there is an unmet need for better tocolytic agents, particularly in low- and middle-income countries. Although most tocolytics, such as betamimetics and indomethacin, suppress downstream mediators of the parturition pathway, newer therapeutics are being designed to selectively target inflammatory checkpoints with the goal of providing broader and more effective tocolysis. However, the relatively small market for new PTB therapeutics and formidable regulatory hurdles have led to minimal pharmaceutical interest and a stagnant drug pipeline. In this review, we present the current landscape of PTB therapeutics, assessing the history of drug development, mechanisms of action, adverse effects, and the updated literature on drug efficacy. We also review the regulatory hurdles and other obstacles impairing novel tocolytic development. Ultimately, we present possible steps to expedite drug development and meet the growing need for effective preterm birth therapeutics.

Magnesium levels in relation to rates of preterm birth: a systematic review and meta-analysis of ecological, observational, and interventional studies

CONTEXT

Experimental studies suggest that magnesium levels in pregnant women may affect the length of gestation, as magnesium affects the activity of smooth muscle in the uterus. Little is known about the association between magnesium levels or supplementation and the rate of preterm birth.

OBJECTIVE

The aim of this systematic review was to summarize the data on magnesium soil levels and preterm birth rates from ecological, observational, and interventional studies.

DATA SOURCES

Soil magnesium levels were obtained from US Geological Survey data, and preterm birth rates were acquired from the March of Dimes Foundation. Relevant epidemiological and clinical studies published until April 2019 in peer-reviewed journals were retrieved from PubMed, Google Scholar, and related reference lists.

STUDY SELECTION

Original studies published in English, conducted in humans, and in which magnesium (dietary/supplemental intake or biomarkers) was an exposure and preterm birth was an outcome were included.

DATA EXTRACTION

Eleven studies were included in the systematic review. Meta-analysis was performed on 6 studies. Overall relative risk (RR) and corresponding 95%CIs for risk of preterm birth in relation to magnesium supplementation were estimated by a random-effects model.

RESULTS

The ecological study revealed an inverse correlation between magnesium content in soil and rates of preterm birth across the United States (r = -0.68; P < 0.001). Findings from 11 observational studies generally support an inverse association between serum magnesium levels and rates of preterm birth. Of the 6 eligible randomized controlled trials, which included 3068 pregnant women aged 20 to 35 years and 352 preterm infants, the pooled RR was 0.58 (95%CI, 0.35-0.96) for women in the magnesium supplementation group compared with women in the control group.

CONCLUSIONS

Accumulated evidence from ecological, observational, and interventional studies consistently indicates that adequate magnesium intake during pregnancy may help reduce the incidence of preterm birth.

Atosiban Combined with Ritodrine for Late Threatened Abortion or Threatened Premature Labor Patients with No Response to Ritodrine: A Clinical Trial

Background

Premature labor is an important cause of infant death and long-term disability. This study aimed to explore the safety and effectiveness of combining the tocolytic agents atosiban and ritodrine to extend gestation.

Material/Methods

The study included 52 patients with late threatened abortion and threatened premature labor between 20^0/7 and 33^6/7 weeks’ gestation who were administrated continuous tocolytic agents for 48 h. Patients were divided into a research group receiving ritodrine combined with atosiban, owing to having no response to ritodrine alone (n=30), and a control group receiving ritodrine alone (n=22). The mean infusion rate and duration of tocolytic administration, gestation extension, pregnancy outcomes, and adverse effects were recorded. Routine blood tests, including C-reactive protein, and cultures for leukorrhea, candida, and mycoplasma were performed before and 1 week after treatment.

Results

Patients receiving ritodrine with atosiban had a mean gestation extension of 42.53±31.70 days. The extension of gestation of the research group was statistically shorter than that of the control group (P<0.05). The fetal loss rate, newborn birth weight, and Apgar score at 1 min were similar between the 2 groups (all, P>0.05). The research group had a lower incidence of palpitations than the control group (P<0.05).

Conclusions

For patients with late threatened abortion or threatened premature labor not controlled with ritodrine alone, ritodrine combined with atosiban extends gestation and improves pregnancy outcomes. For patients with abnormal uterine contractions, routine testing for reproductive tract infection should be performed. When infection is present, anti-infective therapy should be administered.

Different impacts of various tocolytic agents on increased risk of postoperative hemorrhage in preterm labor women undergoing Cesarean delivery: A population-based cohort study

Tocolytic agents, commonly used for inhibiting preterm labor, pose the risk of uterine atony, leading to postpartum hemorrhage. This study elucidated the effects of different tocolytic agents on postoperative hemorrhage among women in preterm labor undergoing Cesarean delivery (CD). Data from Taiwan National Health Insurance Research Database were analyzed. The risk (adjusted hazard ratio [aHR] and 95% confidence intervals [CI]) of postoperative hemorrhage in CD women with preterm labor diagnosis using tocolytic agents (Tocolysis group) comparing to CD women not using tocolytic agents (Control group) were determined. Impacts of different tocolytic agents in this regard were also investigated. Our data revealed that the incidence (11.7% vs 2.6%, P < .001) and risk (aHR: 1.21, 95% CI: 1.12-1.31, P < .001) of postoperative hemorrhage were significantly higher in the Tocolysis group (n = 15,317) than in the Control group (n = 244,096). Ritodrine was the most frequently used tocolytic agent (80.5%), followed by combination therapy (using more than one tocolytic agents) (8.5%), magnesium sulfate (MgSO4, 4.6%), calcium channel blockers (3.8%), betamimetics other than ritodrine (1.9%), prostaglandin synthase inhibitors (0.5%), and nitrates (0.1%). Barring those using calcium channel blockers and combination therapy, the use of MgSO4 (aHR: 1.43, P = .001), betamimetics other than ritodrine (aHR: 1.71, P < .001), prostaglandin synthase inhibitors (aHR: 2.67, P < .001) and nitrates (aHR: 3.30, P = .001) was associated with higher risks of postoperative hemorrhage compared with ritodrine. In conclusion, CD women with preterm labor diagnosis using tocolytic agents exhibit an increased risk of postoperative hemorrhage and that this risk varies with the use of different tocolytic agents.

Effect of magnesium sulfate on baroreflex during acute hypoxemia in chronically instrumented fetal sheep

AIM

To investigate the effects of magnesium sulfate on fetal baroreflex in normoxemia or acute fetal hypoxemia.

METHODS

Fetal baroreflex response was elicited using phenylephrine (30 μg) in saline and magnesium sulfate in 8 chronically treated and instrumented fetal sheep. Hypoxemia was induced using nitrogen gas inflow for 30 min. Baroreflex, calculated as the ratio of the fetal heart rate change to the mean arterial pressure, was monitored after magnesium sulfate administration and in rapid and nonrapid eye movement (NREM) sleep states. Baroreflex was assessed in response to hypoxemia in control groups in both the rapid and NREM sleep states.

RESULTS

Baroreflex was not significantly affected by saline, magnesium sulfate and rapid or NREM sleep states in normoxemic sheep. Hypoxemia increased the baroreflex in the saline-treated group (hypoxemic vs normoxemic rapid eye movement sleep: 4.37 ± 2.48 vs 2.72 ± 0.83; P < 0.05; hypoxemic vs normoxemic NREM sleep: 4.30 ± 1.47 vs 3.15 ± 0.83; P < 0.001). Magnesium sulfate decreased the baroreflex in the hypoxemic fetuses (magnesium sulfate hypoxemic vs. control normoxemic fetuses: 1.42 ± 0.92 vs 3.15 ± 0.83, P < 0.05).

CONCLUSION

The hypoxemic fetal sheep, from the ewes that were receiving magnesium sulfate, showed a significantly reduced in the baroreflex response. In clinical practice, baroreflex-related decelerations in hypoxemic fetuses of mothers receiving magnesium sulfate should be carefully interpreted.

Tocolysis: A Review of the Literature

Importance

Preterm delivery represents an important cause of infant morbidity and mortality. Various tocolytics have been studied with the objective of stopping preterm labor, increasing gestational age at delivery, and preventing complications related to preterm birth.

Objective

This review aims to summarize the major classes of tocolytics and review the evidence regarding use of each.

Evidence Acquisition

A PubMed search of the following terms was performed to gather relevant data: "tocolytic," "preterm labor," "preterm delivery," "PPROM," "magnesium," "indomethacin," "nifedipine," and "betamimetics."

Results

The benefits and risks of nonsteroid anti-inflammatory drugs, calcium channel blockers, magnesium, and betamimetics are reviewed. Calcium channel blockers afford superior outcomes in terms of prolonging gestation and decreasing neonatal morbidity and mortality with the fewest adverse effects.

Conclusions and Relevance

Tocolytics, particularly calcium channel blockers, may provide benefit to pregnant women and their infants. Their use should be tailored to the particular clinical circumstances of the patient and used in conjunction with other management strategies (e.g., administration of corticosteroids for fetal lung maturation or magnesium for neuroprotection and transfer to a tertiary medical center). Further research and professional guidelines are needed on optimal use of these agents.

Acute Tocolysis - a Critical Analysis of Evidence-Based Data

Tocolysis is among the most common obstetric measures. The objective is to prolong the pregnancy by at least 48 hours to complete foetal lung maturation and for the in-utero transfer of the pregnant woman to a perinatal centre. The indication for tocolysis is regular, premature contractions (≥ 4/20 min) and a dynamic shortening of the cervical length/cervical opening between 22 + 0 to 33 + 6 weeks of pregnancy. In this connection, the cervical length measured on ultrasound and the determination of biomarkers in the cervicovaginal secretions can be important decision-making aids. Beta sympathomimetics should no longer be used due to the high rate of severe maternal adverse effects. Given controversial data, magnesium sulphate is no longer recommended for tocolysis in current guidelines. Atosiban is as effective for prolonging pregnancy as beta sympathomimetics and nifedipine, has the lowest rate of maternal adverse effects, but also the highest drug costs. Nifedipine and indomethacin are recommended in international guidelines for acute tocolysis, however there are indications of increased neonatal morbidity following indomethacin. Current problems are, above all, the lack of randomised, controlled comparative and placebo-controlled studies, the data which are controversial to some extent, and the insufficient evidence of tocolytics to significantly improve the neonatal outcome.

A double-blinded, randomized, placebo-controlled trial assessing the effects of nifedipine on embryo transfer: Study protocol

INTRODUCTION

Implantation failure is the main factor affecting the success rate of in vitro fertilization (IVF) procedures. Studies have reported that uterine contractions (UCs) at the time of embryo transfer (ET) were inversely related to implantation and pregnancy rate, hence reducing the success of IVF treatment. Various pharmacological agents, with the exception of calcium channel blocker (CCB), have been investigated to reduce UC. In this regard, we are presenting a proposal for a double-blind randomized placebo-controlled trial. The trial aims to determine whether nifedipine, a CCB with potent smooth muscle relaxing activity and an excellent safety profile, can improve the outcome of ET.

METHODS AND ANALYSES

We will recruit 100 infertile women into one of 2 groups: placebo (n = 50) and nifedipine 20 mg (n = 50). Study participants will be admitted 30 minutes prior to ET and given either tablet after their baseline vital signs have been recorded. They will then undergo ET and be observed for adverse events for another 30 minutes post-ET. The primary outcome will be implantation rate and clinical pregnancy rate. Secondary outcomes include adverse events, miscarriage and pregnancy, and neonatal outcomes. Resulting data will then be analyzed using t test, Chi-square test, and multivariate test to compare outcomes between the 2 groups for any statistical significance. This protocol has been designed in accordance with the SPIRIT 2013 Guidelines.

The combination tocolytic effect of magnesium sulfate and an oxytocin receptor antagonist in myometrium from singleton and twin pregnancies

BACKGROUND

Preterm birth at <37 weeks of gestation is the most common and costly complication of pregnancy and remains the leading cause of neonatal morbidity, death, and reduced achievement in surviving infants. Magnesium sulfate is 1 class of tocolytics for threatened preterm labor; however, its clinical efficacy has been questioned. Twin pregnancies are at increased risk of preterm delivery compared with singleton gestations, which suggests that there is twin-specific risk to preterm delivery in twins. The prevention strategies that are applied to singleton pregnancies, however, have not been shown to be effective in twin pregnancies.

OBJECTIVE

The purpose of this study was to compare the relaxant effect of magnesium sulfate on spontaneous and oxytocin-augmented contractions of human myometrium from singleton and twin pregnancies and to examine whether the effect of oxytocin on magnesium sulfate's potency could be reversed with the use of the oxytocin receptor antagonist, atosiban.

STUDY DESIGN

Myometrium was obtained at the time of prelabor cesarean section (36-40 weeks of gestation) from women with singleton (n=23) or twin (n=12) pregnancy. Isometric tension recordings were made on myometrial strips that were mounted in organ baths that were superfused with physiologic saline solution. Strips were exposed to rising concentrations of magnesium sulfate, and the effect on spontaneous contractions or stimulated with oxytocin (0.5 nmol/L) and in the presence or absence of atosiban (100 nmol/L) was recorded. The contractile characteristics after each application of magnesium sulfate, which included amplitude of contraction and activity integral, were measured. Concentration-response curves were fitted with the use of nonlinear regression and comparison of the negative logarithm of the 50% reduction in activity values.

RESULTS

Magnesium sulfate exerted an equal concentration-dependent inhibitory effect on spontaneous myometrial contractions from both singleton and twin myometrium (P>.05). The application of oxytocin produced a significant rightward shift in the concentration-response curves (P<.0001), but no differences were found between pregnancy groups (P>.05). The addition of atosiban shifted concentration-response curves significantly back to the left for amplitude of contraction and activity integral in singletons (P<.0001). However, only activity integral was significantly reversed in twins (P<.01).

CONCLUSION

Magnesium sulfate is equipotent in suppressing contractions in singleton and twin myometrium. Oxytocin (0.5 nmol/L) significantly reduces the tocolytic potency of magnesium sulfate, which may explain, in part, magnesium sulfate's poor efficacy in vivo; however, this can be reversed partially by the use of an oxytocin receptor antagonist. Combination tocolysis that involves oxytocin receptor antagonists requires further investigation.

Magnesium in pregnancy

Magnesium deficiency is prevalent in women of childbearing age in both developing and developed countries. The need for magnesium increases during pregnancy, and the majority of pregnant women likely do not meet this increased need. Magnesium deficiency or insufficiency during pregnancy may pose a health risk for both the mother and the newborn, with implications that may extend into adulthood of the offspring. The measurement of serum magnesium is the most widely used method for determining magnesium levels, but it has significant limitations that have both hindered the assessment of deficiency and affected the reliability of studies in pregnant women. Thus far, limited studies have suggested links between magnesium inadequacy and certain conditions in pregnancy associated with high mortality and morbidity, such as gestational diabetes, preterm labor, preeclampsia, and small for gestational age or intrauterine growth restriction. This review provides recommendations for further study and improved testing using measurement of red cell magnesium. Pregnant women should be counseled to increase their intake of magnesium-rich foods such as nuts, seeds, beans, and leafy greens and/or to supplement with magnesium at a safe level.

Risks and Benefits of Magnesium Sulfate Tocolysis in Preterm Labor (PTL)

The U.S. Food and Drug Administration issued a drug safety communication on 05/30/2013 recommending "against prolonged use of magnesium sulfate to stop preterm labor (PTL) due to bone changes in exposed babies." In September of 2013, The American Congress of Obstetrics and Gynecologists issued Committee Opinion No. 573 " Magnesium Sulfate Use in Obstetrics" , which supports the short term use of MgSO4 to prolong pregnancy (up to 48 hrs.) to allow for the administration of antenatal corticosteroids." Are these pronouncements by respected organizations short sighted and will potentially result in more harm than good? The FDA safety communication focuses on bone demineralization (a few cases with fractures) with prolonged administration of MgSO4 (beyond 5-7 days). It cites 18 case reports in the Adverse Event Reporting System with an average duration of magnesium exposure of 9.6 weeks (range 8-12 wks). Other epidemiologic studies showed transient changes in bone density which resolved in the short duration of follow up. Interestingly, the report fails to acknowledge the fact that these 18 fetuses were in danger of PTD and the pregnancy was prolonged by 9.6 weeks (e.g. extending 25 weeks to 34.6 wks), thus significantly reducing mortality and morbidity. Evidence does support the efficacy of MgSO4 as a tocolytic medication. The decision to use magnesium, the dosage to administer, the duration of use, and alternative therapies are physician judgments. These decisions should be made based on a reasonable assessment of the risks of the clinical situation (PTL) and the treatments available versus the benefits of significantly prolonging pregnancy.

Practice Bulletin No. 159: Management of Preterm Labor

Preterm birth is the leading cause of neonatal mortality and the most common reason for antenatal hospitalization . In the United States, approximately 12% of all live births occur before term, and preterm labor preceded approximately 50% of these preterm births . Although the causes of preterm labor are not well understood, the burden of preterm births is clear-preterm births account for approximately 70% of neonatal deaths and 36% of infant deaths as well as 25-50% of cases of long-term neurologic impairment in children . A 2006 report from the Institute of Medicine estimated the annual cost of preterm birth in the United States to be $26.2 billion or more than $51,000 per premature infant . However, identifying women who will give birth preterm is an inexact process. The purpose of this document is to present the various methods proposed to manage preterm labor and to review the evidence for the roles of these methods in clinical practice. Identification and management of risk factors for preterm labor are not addressed in this document.

Use and attitudes of obstetricians toward 3 high-risk interventions in MFMU Network hospitals

OBJECTIVE

We sought to evaluate the frequency of, and factors associated with, the use of 3 evidence-based interventions: antenatal corticosteroids for fetal lung maturity, progesterone for prevention of recurrent preterm birth, and magnesium sulfate for fetal neuroprotection.

STUDY DESIGN

A self-administered survey was conducted from January through May 2011 among obstetricians from 21 hospitals that included 30 questions regarding their knowledge, attitudes, and practice of the 3 evidence-based interventions and the 14-item short version of the Team Climate for Innovation survey. Frequency of use of each intervention was ascertained from an obstetrical cohort of women between January 2010 and February 2011.

RESULTS

A total of 329 obstetricians (74% response rate) who managed 16,946 deliveries within the obstetrical cohort participated in the survey. More than 90% of obstetricians reported that they incorporated each intervention into routine practice. Actual frequency of administration in women eligible for the treatments was 93% for corticosteroids, 39% for progesterone, and 71% for magnesium sulfate. Provider satisfaction with quality of treatment evidence was 97% for corticosteroids, 82% for progesterone, and 57% for magnesium sulfate. Obstetricians perceived that barriers to treatment were most frequent for progesterone (76%), 30% for magnesium sulfate, and 17% for corticosteroids. Progesterone use was more frequent among patients whose provider reported the quality of the evidence was above average to excellent compared with poor to average (42% vs 25%, respectively; P < .001), and they were satisfied with their knowledge of the intervention (41% vs 28%; P = .02), and was less common among patients whose provider reported barriers to hospital or pharmacy drug delivery (31% vs 42%; P = .01). Corticosteroid administration was more common among patients who delivered at hospitals with 24 hours a day-7 days a week maternal-fetal medicine specialist coverage (93% vs 84%; P = .046), CONCLUSION: Obstetricians in Maternal-Fetal Medicine Units Network hospitals frequently use these evidence-based interventions; however, progesterone use was found to be related to their assessment of evidence quality. Neither progesterone nor the other interventions were associated with overall climate of innovation within a hospital as measured by the Team Climate for Innovation. National Institutes of Health Consensus Conference Statements may also have an impact on use; there is such a statement for antenatal corticosteroids but not for progesterone for preterm prevention or magnesium sulfate for fetal neuroprotection.

Does magnesium sulfate delay the active phase of labor in women with premature rupture of membranes? A randomized controlled trial

OBJECTIVE

Administration of many drugs including magnesium sulfate (MS) has considerable influences on pregnancy outcomes. The present study investigates the effects of MS administration on reaching the active phase of labor in women with premature rupture of membrane (PROM) and subsequent fetal complications.

MATERIALS AND METHODS

A double blind, randomized, placebo-controlled trial was performed among primipara women referred to the PROM center in Tehran, Iran between March 2010 and August 2012. Patients were equally allocated into two groups; the intervention group who received MS (n = 46) and the control (placebo) group (n = 46). Both groups received a corticosteroid, 1g oral azithromycin (oral) and 2 g ampicillin (IV) every 6 hours for 48 hours, followed by amoxicillin (500 mg orally 3 times daily) for an additional 5 days. None of the research staff were aware of the treatment allocation of patients in order for blinding purposes.

RESULTS

Administration of MS in intervention group increases this period 2.7 times compared to the control group. In women whose gestational age was <30 weeks, MS administration increased the active phase of labor up to 77%. Administration of magnesium sulfate reduced the risk of respiratory distress syndrome significantly (p = 0 .002), without producing any adverse pregnancy outcomes.

CONCLUSION

Magnesium sulfate increases delay in reaching the active phase of labor in mothers with PROM, without producing adverse birth outcomes. (Registration ID in IRCT; IRCT2012091810876N1).

Factors affecting maternal serum magnesium levels during long-term magnesium sulfate tocolysis in singleton and twin pregnancy

AIM

Our aim was to determine factors that affect maternal serum magnesium (Mg) levels, to help ensure the safety and efficacy of long-term magnesium sulfate (MgSO4 ) therapy for threatened preterm labor in singleton and twin pregnancies.

MATERIAL AND METHODS

We retrospectively and arbitrarily studied 100 patients (singleton pregnancy, n = 65; twin pregnancy, n = 35) who received i.v. MgSO4 for >48 h for tocolysis of threatened preterm labor. We used multiple regression analysis to investigate the functional relations between the candidate factors and maternal serum Mg levels.

RESULTS

MgSO4 was administered as a loading dose of 3 g for 1 h followed by a maintenance dose of 1.0-2.0 g/h. There were no maternal severe adverse events related to the elevated Mg levels in any of the subjects. The results of multiple regression analysis revealed that total dose of MgSO4 for 24 h before blood collection (g/day), total serum protein level (g/dL), serum total calcium level (mg/dL), serum creatinine level (mg/dL) and maternal bodyweight (kg) significantly affected maternal serum Mg levels in both singleton and twin pregnancies (all P-values were < 0.001). Gestational age (weeks) and period of MgSO4 administration (days) at blood collection had no significant effect in singleton or twin pregnancies.

CONCLUSION

Our study statistically shows that dose of MgSO4 , total serum protein level, serum total calcium level, serum creatinine level and maternal bodyweight are key factors to achieving safe and effective long-term tocolysis with MgSO4 in not only singleton but also twin pregnancies.

Antenatal magnesium sulfate exposure and acute cardiorespiratory events in preterm infants

OBJECTIVE

Antenatal magnesium (anteMg) is used for various obstetric indications including fetal neuroprotection. Infants exposed to anteMg may be at risk for respiratory depression and delivery room (DR) resuscitation. The study objective was to compare the risk of acute cardiorespiratory events among preterm infants who were and were not exposed to anteMg.

STUDY DESIGN

This was a retrospective analysis of prospective data collected in the Eunice Kennedy Shriver National Institute of Child Health and Human Development Neonatal Research Network's Generic Database from April 1, 2011, through March 31, 2012. The primary outcome was DR intubation or respiratory support at birth or on day 1 of life. Secondary outcomes were invasive mechanical ventilation, hypotension treatment, neonatal morbidities, and mortality. Logistic regression analysis evaluated the risk of primary outcome after adjustment for covariates.

RESULTS

We evaluated 1544 infants <29 weeks' gestational age (1091 in anteMg group and 453 in nonexposed group). Mothers in the anteMg group were more likely to have higher education, pregnancy-induced hypertension, and antenatal corticosteroids, while their infants were younger in gestation and weighed less (P < .05). The primary outcome (odds ratio [OR], 1.2; 95% confidence interval [CI], 0.88-1.65) was similar between groups. Hypotension treatment (OR, 0.70; 95% CI, 0.51-0.97) and invasive mechanical ventilation (OR, 0.54; 95% CI, 0.41-0.72) were significantly less in the anteMg group.

CONCLUSION

Among preterm infants age <29 weeks' gestation, anteMg exposure was not associated with an increase in cardiorespiratory events in the early newborn period. The safety of anteMg as measured by the need for DR intubation or respiratory support on day 1 of life was comparable between groups.

Prevention of preterm birth in modern obstetrics

Spontaneous preterm labor is a complex process characterized by the interplay of multiple different pathways. Prevention of preterm labor and delivery is also complicated. The most effective interventions for prevention of preterm birth (PTB) are progestin prophylaxis and lifestyle modifications, with cerclage placement also playing a role in selected populations. Interventions such as activity modification, home tocometry, and routine antibiotic use have fallen out of favor because of lack of effectiveness and possibility of harm. The solution to the problem of PTB remains elusive, and researchers and clinicians must collaborate to find a cure for preterm labor.

Oxidative stress damage as a detrimental factor in preterm birth pathology

Normal term and spontaneous preterm births (PTB) are documented to be associated with oxidative stress (OS), and imbalances in the redox system (balance between pro- and antioxidant) have been reported in the maternal-fetal intrauterine compartments. The exact mechanism of labor initiation either at term or preterm by OS is still unclear, and this lack of understanding can partially be blamed for failure of antioxidant supplementation trials in PTB prevention. Based on recent findings from our laboratory, we postulate heterogeneity in host OS response. The physiologic (at term) and pathophysiologic (preterm) pathways of labor are not mediated by OS alone but by OS-induced damage to intrauterine tissues, especially fetal membranes of the placenta. OS damage affects all major cellular elements in the fetal cells, and this damage promotes fetal cell senescence (aging). The aging of the fetal cells is predominated by p38 mitogen activated kinase (p38MAPK) pathways. Senescing cells generate biomolecular signals that are uterotonic, triggering labor process. The aging of fetal cells is normal at term. However, aging is premature in PTB, especially in those PTBs complicated by preterm premature rupture of the membranes, where elements of redox imbalances and OS damage are more dominant. We postulate that fetal cell senescence signals generated by OS damage are likely triggers for labor. This review highlights the mechanisms involved in senescence development at term and preterm by OS damage and provides insight into novel fetal signals of labor initiation pathways.

Short-term tocolytics for preterm delivery - current perspectives

Administration of short-term tocolytic agents can prolong pregnancy for women in preterm labor. Prolonging pregnancy has many benefits because it allows for other proven interventions, such as antenatal corticosteroid administration, to be accomplished. This review provides an overview of currently utilized tocolytic agents and the evidence demonstrating their efficacy for prolonging pregnancy by at least 48 hours. General pharmacological principles for the clinician regarding drugs in pregnancy are also briefly discussed. In general, while the choice of the best first-line short-term tocolytic drug is not clear, it is evident that use of these agents has a clear place in current obstetric therapeutics.

Proteomic analysis of cervical vaginal fluid proteins among women in recurrent preterm labor

OBJECTIVE

Proteomic analysis of four cervical-vaginal fluid (CVF) proteins to identify biomarkers of recurrent preterm birth (rPTB) in at-risk women prior to onset of preterm labor.

METHODS

Nested case control study from 2007 to 2011 of women with prior spontaneous preterm birth(s) (PTB) who underwent serial CVF sampling. Mass spectrometry analysis was used and ELISA analysis was performed to validate candidates.

RESULTS

108 patients were enrolled and 10 cases and 20 gestational age matched controls were analyzed after exclusions. Of 748 CVF proteins identified, 72 had statistically significant (p < 0.05) expression differences and 38 were highly differentially expressed (p < 0.01). Four candidate proteins were abundant and involved in immune/inflammatory response, but ELISA analysis did not confirm altered expression patterns.

CONCLUSION

The lack of confirmation of potential biomarkers identified by mass spectrometry and ELISA demonstrates the challenges of validating PTB biomarkers and suggests that a panel of biomarkers would improve the predictive value of CVF testing.

A comparison of three tocolytics for preterm labor: a randomized clinical trial

OBJECTIVE

To compare the efficacy and maternal side effects of nifedipine (N), magnesium sulfate (M), and indomethacin (I) for acute tocolysis.

METHODS

In this single center randomized trial, women in preterm labor 24-32 weeks' gestation received intravenous M, oral N, or I suppositories. The primary outcomes of interest were arrest of preterm labor (>48 h, ≥7 days), gestational age at delivery, and maternal side effects.

RESULTS

Over a 38-month period, 301 women were allocated to receive M (90), N (114), or I (90). Gestational age at delivery (p = 0.551) or arrest of labor >48 h, >7 days were similar between the three groups (p = 0.199, 0.654). Hypotension and tachycardia were more common in N patients compared to women receiving M or I (p = 0.003, 0.009). Patients receiving I had more fetal ductal constriction or oligohydramnios compared to M or N (p = 0.001, 0.020) but, I women were tested more often. There was one case of pulmonary edema in the M group and one with plural effusion in the N group.

CONCLUSION

There were no differences in efficacy or in major maternal safety issues between the three tocolytic agents. Since there is no FDA approved tocolytic to treat preterm labor, clinicians should use the tocolytic that has afforded them the best results with the least maternal/neonatal side effects.

Ritodrine for intractable uterine pain due to extrapelvic malignant tumor metastases: a case report

BACKGROUND

Effective pain management is an essential component of cancer treatment as approximately 75% of all cancer patients experience excruciating nociceptive pain even at maximum safe doses of nonsteroidal anti-inflammatory drugs and/or opioids. We report a case where ritodrine hydrochloride effectively controlled refractory pain due to uterine metastases from thymic carcinoma.

CASE PRESENTATION

A 40-year-old woman presented at our hospital with chest discomfort, severe right femoral pain, and intermittent hypogastralgia. Computed tomography, magnetic resonance imaging, and positron emission tomography revealed a large mass in the anterior mediastinum, multiple nodules in the lungs, and multiple metastases on the uterus, lumbar vertebrae, and pelvic bones. Needle biopsies of the mediastinal and uterine cervical tumors revealed undifferentiated carcinoma of the thymus metastasizing to the uterus. Oxycodone and nonsteroidal anti-inflammatory drugs relieved the right femoral pain but not the hypogastralgia. We speculated that hypogastralgia did not result from somatalgia but from splanchnodynia. Ritodrine was administered in an effort to inhibit uterine contractions and to reduced the refractory pain and improved her quality of life.

CONCLUSION

Ritodrine relieved the pain caused by uterine contraction due to metastases and enhanced the quality of life.

Effect of magnesium sulfate exposure on term neonates

OBJECTIVE

To compare neonatal intensive care unit and special care unit (NICU) admission rates between term neonates exposed to antenatal magnesium sulfate (MS) and those unexposed.

STUDY DESIGN

We performed a retrospective cohort study of all singleton neonates ≥37 weeks born to women with pre-eclampsia from August 2006 to July 2008. Cases were defined by antenatal exposure to MS and controls by absence of MS exposure. The primary outcome was NICU admission. Data were analyzed via univariable and multivariable regression analyses.

RESULT

In all, 28 (14.7%) out of 190 MS-exposed neonates ≥37 weeks were admitted to the NICU, compared with 4 (5.4%) of 74 non-exposed neonates (P=0.04). This association persisted after controlling for potential confounding variables including severe pre-eclampsia and cesarean delivery (AOR 3.69, 1.13 to 11.99). NICU admission was associated in a dose-dependent relationship with total hours and mean dose of MS exposure. Number needed to harm with MS was 11 per NICU admission. Among neonates admitted to the NICU, MS-exposed were more likely to require fluid and nutritional support than unexposed neonates (60.7 vs 0%, P=0.04), and trended toward more frequent requirement for respiratory support and greater length of stay.

CONCLUSION

In term neonates, MS exposure may be associated independently with NICU admission in a dose-dependent relationship. Requirements for fluid and nutritional support are common in this group, likely due to feeding difficulties in exposed neonates. Assessment of acute care needs among all neonates exposed to MS for maternal eclampsia prophylaxis should be considered.

Magnesium sulfate during anticipated preterm birth for infant neuroprotection

Advances in medical care of preterm infants, including the widespread use of surfactant and antenatal steroids, and improvements in ventilation management, have increased the survival rates of some of the most vulnerable infants. Yet, the risk of neurologic impairment and long-term medical complications remains a concern. Recently, the use of magnesium sulfate during anticipated preterm birth has been identified as a potential treatment to reduce adverse neurologic outcomes among preterm infants. This article discusses the use of magnesium sulfate for anticipated preterm birth to reduce neurologic impairment in preterm infants, including current clinical practice guidelines and implications for nurses.

Biological mechanisms for nutritional regulation of maternal health and fetal development

This review paper highlights mechanisms for nutritional regulation of maternal health and fetal development. Malnutrition (nutrient deficiencies or obesity) in pregnant women adversely affects their health by causing or exacerbating a plethora of problems, such as anaemia, maternal haemorrhage, insulin resistance, and hypertensive disorders (e.g. pre-eclampsia/eclampsia). Maternal malnutrition during gestation also impairs embryonic and fetal growth and development, resulting in deleterious outcomes, including intrauterine growth restriction (IUGR), low birthweight, preterm birth, and birth defects (e.g. neural tube defects and iodine deficiency disorders). IUGR and preterm birth contribute to high rates of neonatal morbidity and mortality. Major common mechanisms responsible for malnutrition-induced IUGR and preterm birth include: (i) abnormal growth and development of the placenta; (ii) impaired placental transfer of nutrients from mother to fetus; (iii) endocrine disorders; and (iv) disturbances in normal metabolic processes. Activation of a series of physiological responses leading to premature and sustained contraction of the uterine myometrium also results in preterm birth. Recent epidemiologic studies have suggested a link between IUGR and chronic metabolic disease in children and adults, and the effects of IUGR may be carried forward to subsequent generations through epigenetics. While advanced medical therapies, which are generally unavailable in low-income countries, are required to support preterm and IUGR infants, optimal nutrition during pregnancy may help ameliorate many of these problems. Future studies are necessary to develop effective nutritional interventions to enhance fetal growth and development and alleviate the burden of maternal morbidity and mortality in low- and middle-income countries.

Association of cord blood magnesium concentration and neonatal resuscitation

OBJECTIVE

To assess the relationship between umbilical cord blood magnesium concentration and level of delivery room resuscitation received by neonates.

STUDY DESIGN

This was a secondary analysis of a controlled fetal neuroprotection trial that enrolled women at imminent risk for delivery between 24 and 31 weeks' gestation and randomly allocated them to receive either intravenous magnesium sulfate or placebo. The cohort included 1507 infants with data available on total cord blood Mg concentration and delivery room resuscitation. Multivariate logistic regression was used to estimate the association between cord blood Mg concentration and highest level of delivery room resuscitation, using the following hierarchy: none, oxygen only, bag-mask ventilation with oxygen, intubation, and chest compressions.

RESULTS

There was no relationship between cord blood Mg and delivery room resuscitation (OR, 0.92 for each 1.0-mEq/L increase in Mg; 95% CI, 0.83-1.03). Maternal general anesthesia was associated with increased neonatal resuscitation (OR, 2.51; 95% CI, 1.72-3.68). Each 1-week increase in gestational age at birth was associated with decreased neonatal resuscitation (OR, 0.63; 95% CI, 0.60-0.66).

CONCLUSION

Cord blood Mg concentration does not correlate with the level of delivery room resuscitation of infants exposed to magnesium sulfate for fetal neuroprotection.

Different magnesium sulphate regimens for neuroprotection of the fetus for women at risk of preterm birth

BACKGROUND

The effectiveness of antenatal magnesium sulphate for neuroprotection of the fetus, infant, and child prior to very preterm birth, when given to women considered at risk of preterm birth, has been established. There is currently no consensus as to the regimen to use in terms of the dose, duration, the use of repeat dosing and timing.

OBJECTIVES

To assess the comparative effectiveness and adverse effects of different magnesium sulphate regimens for neuroprotection of the fetus in women considered at risk of preterm birth.

SEARCH METHODS

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

SELECTION CRITERIA

Randomised trials comparing different magnesium sulphate regimens when used for neuroprotection of the fetus in women considered at risk of preterm birth. We planned to include cluster trials. We planned to exclude quasi-randomised trials and those with a crossover design. We planned to include trials published as full-text papers, along with those published in abstract form only.

DATA COLLECTION AND ANALYSIS

We planned that at least two review authors would assess trial eligibility.

MAIN RESULTS

No eligible completed trials were identified.

AUTHORS' CONCLUSIONS

Although strong evidence supports the use of antenatal magnesium sulphate for neuroprotection of the fetus prior to very preterm birth, no trials comparing different treatment regimens have been completed. Research should be directed towards comparisons of different dosages and other variations in regimens, evaluating both maternal and infant outcomes.

Tocolytic therapy for acute preterm labor

The pathophysiology leading to preterm labor is not well understood and often multifactorial; initiating factors include intrauterine infection, inflammation, ischemia, overdistension, and hemorrhage. Given these different potential causes, directing therapy for preterm labor has been difficult and suboptimal. To date, no single drug has been identified as successful in treating all of the underlying mechanisms leading to preterm labor. In addition, the methodology of many of the tocolytic studies is limited by lack of sufficient patient numbers, lack of comparison with a placebo, and inconsistent use of glucocorticoids. The limitations in these individual studies make it difficult to evaluate the efficacy of a single tocolytic by meta-analysis. Despite these limitations, the goals for tocolysis for preterm labor are clear: To complete a course of glucocorticoids and secure the appropriate level of neonatal care for the fetus in the event of preterm delivery. The literature demonstrates that many tocolytic agents inhibit uterine contractility. The decision as to which tocolytic agent should be used as first-line therapy for a patient is based on multiple factors, including gestational age, the patient’s medical history, common and severe side effects, and a patient’s response to therapy. In a patient at less than 32 weeks gestation, indomethacin may be a reasonable first choice based on its efficacy, ease of administration, and minimal side effects. Concurrent administration of magnesium for neuroprotection may be given. At 32 to 34 weeks, nifedipine may be a reasonable first choice because it does not carry the fetal risks of indomethacin at these later gestational ages, is easy to administer, and has limited side effects relative to beta-mimetics. In an effort to review a commonly faced obstetrical complication, this article has provided a summary of the most commonly used tocolytics, their mechanisms of action, side effects, and clinical data regarding their efficacy.

Magnesium sulfate: past, present, and future

First used anecdotally for the control of eclamptic seizures in the early 1900s, magnesium sulfate remains 1 of the most commonly used medications in obstetric practice today. Over the past 95 years, there have been countless research studies investigating the efficacy of magnesium sulfate for the management of eclampsia, preeclampsia, preterm labor, and most recently for prevention of cerebral palsy. The majority of this evidence undeniably supports the use of magnesium sulfate as the drug of choice for the prevention and treatment of eclampsia when evidence of severe disease is present. On the other hand, studies have not shown magnesium sulfate to be comparably more effective than other tocolytics for treating preterm labor, nor is there agreement on whether the evidence supports its use as a neuroprotective agent for prevention of cerebral palsy. The exact mechanism of action of magnesium sulfate remains largely hypothetical, and parenteral use has the potential to cause significant morbidity in high doses. This article reviews magnesium sulfate's remarkable history in obstetric practice and includes a summary of the evidence related to each of the controversies. An initial review of the physiology of magnesium sulfate is essential to understanding pharmacodynamic actions, dosing guidelines, and safety requirements.

Inhibition of epoxy-eicosanoid degradation improves the tocolytic effects of indomethacin in the uterus from pregnant women

The incidence of preterm birth is an increasing problem. Indomethacin, a non-specific cyclooxygenase inhibitor, has been largely used as tocolytic in the treatment of preterm labor. The aim of the present study was to assess a putative synergistic tocolytic effect between the inhibition of the production of prostanoids and stabilization of epoxides fatty acids, particularly arachidonate on spontaneous uterine contractile activity. The experimental work was performed on uterine biopsies from consenting women undergoing elective cesarean delivery at term. Isometric tension measurements were performed on fresh human myometrial strips. Contractile activities have been monitored upon individual and combined treatments of indomethacin, DDMS, an inhibitor of hydroxy-eicosanoids production and AUDA, an inhibitor of epoxy-eicosanoids degradation. Interestingly, a significant and consistent synergic effect was observed when indomethacin and AUDA were simultaneously added, raising the possibility of a combined clinical use of cyclooxygenase and sEH inhibitors in attempt to treat preterm labor.

The risk of necrotizing enterocolitis after indomethacin tocolysis

BACKGROUND

Postnatal indomethacin is reportedly associated with an increased incidence of necrotizing enterocolitis (NEC) in preterm infants. Because indomethacin readily crosses the placenta, we hypothesized that antenatal indomethacin (AI) would increase the risk for NEC in preterm infants.

OBJECTIVE

The goal of this study was to explore the association between AI and NEC in preterm infants.

METHODS

Medical records of preterm infants, 23 to 32 weeks' gestational age, without major congenital anomalies, were reviewed. Maternal and neonatal data were abstracted. Association of AI within 15 days before delivery (predictor variable) and classification of NEC according to modified Bell's stage 2a or higher in the first 15 days after delivery (early NEC [primary outcome variable]) was explored by using bivariate analyses, multivariate logistic regression, and propensity score analysis.

RESULTS

Of 628 eligible infants, 63 received AI and 28 developed early NEC. AI exposure was significantly associated with multiple gestation, race, antenatal corticosteroids and magnesium sulfate, lower birth weight and gestational age, umbilical arterial catheter placement, respiratory distress syndrome, postnatal vasopressors and antibiotics, patent ductus arteriosus, sepsis, NEC, intraventricular hemorrhage, and mortality. On multivariate logistic regression controlling for covariates, AI was significantly associated with early NEC (adjusted odds ratio: 7.193 [95% confidence interval: 2.514-20.575]; number needed to harm: 5). The results remained significant when analyses were repeated using AI exposure within 5 days before delivery as a predictor variable; on analyses stratified according to gestational age; and on propensity score analysis.

CONCLUSIONS

AI was associated with NEC in preterm infants in the first 15 days of life in this study, as were multiple other clinical factors.

Using prophylactic, but not tocolytic, magnesium sulfate to reduce cerebral palsy related to prematurity: what dose, and what about infant mortality?

Strategies for the prevention of cerebral palsy (CP) remain incompletely characterized. Recognizing that half of all cases are associated with preterm delivery (Australian CP Register Report, 2009), research protocols aimed at reducing its prevalence have focused on interventions in pregnancies at risk for preterm birth. Compelling data from recent clinical trials have led to an emerging consensus favoring the use of antenatal magnesium sulfate for preterm neuroprophylaxis. Unresolved, however, is the critical question regarding the "best dose". Acknowledging that any substance in high enough doses becomes toxic, the "best dose" is really the least dose that achieves efficacy, while minimizing potential toxicity among susceptible fetuses. Importantly, credible evidence from these CP prevention trials indicates that antenatal magnesium sulfate, if dosed appropriately, may also decrease infant mortality--a worthy goal in its own right. Accordingly, whether we achieve (a) reduction in CP only, (b) simultaneous reduction in CP and infant mortality, or (c) CP reduction offset by possibly increased pediatric mortality, may depend on selection of dose. In this Opinion paper, we review the findings of all major randomized trials that tested the magnesium hypothesis for prevention of CP. In addition, we discuss future research, in progress, that is hoped to refine estimates of best dose.

Magnesium sulfate as a second-line tocolytic agent for preterm labor: a randomized controlled trial in Kyushu Island

Objectives. We evaluated the efficacy of magnesium sulfate as a second-line tocolysis for 48 hours. Materials and Methods. A multi-institutional, simple 2-arm randomized controlled trial was performed. Forty-five women at 22 to 34 weeks of gestation were eligible, whose ritodrine did not sufficiently inhibit uterine contractions. After excluding 12 women, 33 were randomly assigned to either magnesium alone or combination (ritodrine and magnesium). The treatment was determined as effective if the frequency of uterine contraction was reduced by 30% at 48 hours of the treatment. Results. After magnesium sulfate infusion, 90% prolonged their pregnancy for >48 hours. Combination therapy was effective in 95% (18/19), which was significantly higher than 50% (7/14) for magnesium alone. Conclusion. This randomized trial revealed that combination therapy significantly reduced uterine contractions, suggesting that adjuvant magnesium with ritodrine is recommended, rather than changing into magnesium alone, when uterine contractions are intractable with ritodrine infusion.