Fetal cardiovascular function during prolonged magnesium sulfate tocolysis

Antenatal magnesium sulphate and delayed passage of meconium: A multicentre study

INTRODUCTION

The published evidence on the association between magnesium sulphate (MgSO₄) and delayed passage of meconium (DPM) is contradictory.

OBJECTIVES

To determine whether there is an association between the administration of MgSO₄ to the mother and DPM in the neonate, and to analyse serum magnesium levels in neonates in relation to the cumulative dose of MgSO₄ administered to the mother.

POPULATION AND METHODS

Retrospective and prospective descriptive and analytical study conducted in patients delivered at or before 32 weeks of gestation in 2 tertiary care hospitals. Delayed passage of meconium was defined as failure to pass meconium within 48 h of birth and/or need for rectal stimulation on 2 or more occasions to pass stool and/or interval of at least 48 h between the first and second bowel movements.

RESULTS

The study included 283 patients (204 retrospectively and 79 prospectively), of who 152 (53.7%) experienced DPM. Delayed passage of meconium was not associated with antenatal MgSO₄ administration, the cumulative maternal MgSO4 dose or neonatal serum magnesium levels. Older gestational age (OR, 0.8; confidence interval [CI], 0.69-0.93; P = 0.003) was an independent protective factor against DPM, while the need for advanced resuscitation (OR, 2.24; CI 1.04-4.86; P = 0.04) was a risk factor for DPM.

CONCLUSION

The neonatal serum levels of magnesium reached with the doses of MgSO₄ administered to mothers were not associated with DPM. Lower gestational age and the need for advanced resuscitation were predictors associated with an increased risk of DPM.

A Review on the Vagus Nerve and Autonomic Nervous System During Fetal Development: Searching for Critical Windows

The autonomic nervous system (ANS) is one of the main biological systems that regulates the body's physiology. Autonomic nervous system regulatory capacity begins before birth as the sympathetic and parasympathetic activity contributes significantly to the fetus' development. In particular, several studies have shown how vagus nerve is involved in many vital processes during fetal, perinatal, and postnatal life: from the regulation of inflammation through the anti-inflammatory cholinergic pathway, which may affect the functioning of each organ, to the production of hormones involved in bioenergetic metabolism. In addition, the vagus nerve has been recognized as the primary afferent pathway capable of transmitting information to the brain from every organ of the body. Therefore, this hypothesis paper aims to review the development of ANS during fetal and perinatal life, focusing particularly on the vagus nerve, to identify possible "critical windows" that could impact its maturation. These "critical windows" could help clinicians know when to monitor fetuses to effectively assess the developmental status of both ANS and specifically the vagus nerve. In addition, this paper will focus on which factors-i.e., fetal characteristics and behaviors, maternal lifestyle and pathologies, placental health and dysfunction, labor, incubator conditions, and drug exposure-may have an impact on the development of the vagus during the above-mentioned "critical window" and how. This analysis could help clinicians and stakeholders define precise guidelines for improving the management of fetuses and newborns, particularly to reduce the potential adverse environmental impacts on ANS development that may lead to persistent long-term consequences. Since the development of ANS and the vagus influence have been shown to be reflected in cardiac variability, this paper will rely in particular on studies using fetal heart rate variability (fHRV) to monitor the continued growth and health of both animal and human fetuses. In fact, fHRV is a non-invasive marker whose changes have been associated with ANS development, vagal modulation, systemic and neurological inflammatory reactions, and even fetal distress during labor.

Impact of tocolysis-intent magnesium sulfate and beta-adrenergic agonists on perinatal brain damage in infants born between 28-36 weeks' gestation

AIMS

Magnesium sulfate has neuroprotective effects in preterm infants. Whether other antepartum treatments interfere with the neuroprotective actions is not well known. This study aims to explore the impacts of antenatal administration of Magnesium sulfate or beta-2 adrenergic agonists as tocolytic agents on the developing brain in premature infants.

METHODS

This is a retrospective cohort study in four tertiary perinatal centers in Japan. We collected data of pregnant women and infants born between 28 and 36 weeks for tocolytic agents, gestational age, sex, antenatal corticosteroid, fetal growth restriction, pathological chorioamnionitis, low umbilical arterial pH values (<7.1), multiple pregnancy, mode of delivery and institutions after excluding clinical chorioamnionitis, non-reassuring fetal status or major anomalies. Tocolytic agents were categorized into four groups: no-tocolysis, magnesium sulfate, beta-2 adrenergic agonists and the combination of them. We conducted multiple comparisons with multivariate analyses using generalized linear regression models to compare the prevalence of a poor perinatal outcome defined as infant's death, brain damage, particularly cerebral palsy and developmental delay.

RESULTS

Among 1083 infants, 39% were no-tocolysis, 47% were magnesium sulfate, 41% were beta-2 adrenergic agonists and 27% were combination group, including the duplication. The incidence of poor perinatal outcome was decreased by magnesium sulfate (OR 0.27, 95% CI 0.10-0.72), but not changed significantly by beta-2 adrenergic agonists (OR 1.28, 95% CI 0.63-2.59) or the combination group (OR 2.24, 95% CI 0.67-7.54), compared with the no-tocolysis.

CONCLUSION

The combination therapy for tocolysis with beta-2 adrenergic agonists diminished the magnesium sulfate neuroprotective action after adjusting for covariables.

Effect of magnesium sulfate on fetal heart rate patterns in the second stage of labor

OBJECTIVE

To estimate the effect of maternal exposure to magnesium sulfate on fetal heart rate characteristics during active labor.

METHODS

Within a 4-year retrospective cohort study of consecutive term deliveries reaching the second stage of labor, we compared women exposed to magnesium for severe preeclampsia to all women not exposed. Primary outcome was the electronic fetal monitoring tracing in the 30 minutes preceding delivery. Secondary outcomes were fetal acidemia and nursery disposition. Attributable risk estimates and multivariable logistic regression were used to estimate the association between magnesium exposure and fetal heart rate characteristics. Unadjusted risk estimates for the association between fetal heart rate characteristics and neonatal outcomes were generated stratified by group.

RESULTS

Of 5,387 women, 248 (4.6%) were exposed to magnesium. Magnesium exposure was associated with lower fetal heart rate baseline (136.9 ± 12.3 beats per minute compared with 139.0 ± 13.5 beats per minute; P=.02), increased risk of baseline less than 120 beats per minute (adjusted odds ratio [OR] 1.76, 95% confidence interval [CI] 1.21-2.56), and increased risk of absent or minimal variability (adjusted OR 2.41, 95% CI 1.78-3.27). More than 20% increased frequency of ever absent or minimal variability was attributable to magnesium (attributable risk 0.21, 95% CI 0.15-0.27). There were no significant differences in presence or number of accelerations or decelerations; however, magnesium was associated with fewer prolonged decelerations (adjusted OR 0.64, 95% CI 0.49-0.84). After excluding women with adverse neonatal outcomes, these associations remained.

CONCLUSION

Maternal exposure to magnesium is associated with lower fetal heart rate baseline within the accepted normal range, decreased variability, and fewer prolonged decelerations without evidence of adverse effect on neonatal outcome.

LEVEL OF EVIDENCE

II.

Antenatal exposure to magnesium sulfate and the incidence of patent ductus arteriosus in extremely low birth weight infants

OBJECTIVE

Magnesium sulfate (MgSO(4)) is the most commonly used tocolytic agent in the US and is also employed as a prophylactic agent against seizures in pre-eclamptic women. MgSO(4) crosses the placenta and its concentration in the newborn usually exceeds that of maternal levels. The purpose of this study was to explore the relationship between antenatal exposure to MgSO(4) and the incidence of patent ductus arteriosus (PDA) in extremely low birth weight infants.

STUDY DESIGN

A total of 954 neonates with birth weights between 500 and 1000 g, born at the University of Miami/Jackson Memorial Hospital between January 1995 and December 2004 and surviving for more than 3 days, were followed until death or discharge from the hospital. The incidence of PDA in infants exposed to MgSO(4) was compared with those not exposed and comparisons were also made between infants exposed to different maternal doses of MgSO(4).

RESULTS

The incidence of PDA was significantly higher in the group of infants exposed to MgSO(4) compared with the unexposed control group (67 vs. 60%, P<0.018). When stratified by gestational age the differences were significant only in the group of infants with a gestational age of >or=26 weeks (58 vs. 49%, P<0.039). Logistic regression analysis to adjust for co-variables indicated an increased risk of PDA with higher doses of MgSO(4) (odds ratio 1.33 confidence interval (CI) 1.12 to 1.58, per 50 g of MgSO(4)).

CONCLUSION

Antenatal exposure to MgSO(4) is associated with a higher risk of PDA in extremely low birth weight infants and this effect is more significant and dose-related in more mature infants.

Cord blood lipoprotein profile after magnesium sulphate treatment in pre-eclamptic patients

AIM

To determine lipoprotein metabolism alterations in magnesium-exposed neonates of women with pre-eclampsia.

METHODS

The study group comprised seven singleton neonates of women with pre-eclampsia at term and treated with magnesium sulphate. Controls were 26 neonates of uncomplicated pregnancies of term delivery. Total serum magnesium concentrations were analysed by the photometric colour method. Total serum cholesterol, triglycerides and high-density lipoprotein cholesterol (HDL-C) levels were determined by enzymatic colour methods, while apoprotein (apo) A-I and apo B values were measured by immunoturbidimetry. Low-density lipoprotein cholesterol (LDL-C) levels were calculated by Friedewald's formula. Very-low-density lipoprotein cholesterol levels, total cholesterol/ HDL-C, apo B/apo A-I, LDL-C/apo B, LDL-C/HDL-C, and HDL-C/apo A-I ratios were determined by calculation.

RESULTS

Magnesium levels of magnesium-exposed neonates were found to be 1.6 times higher than those of controls. Magnesium-exposed neonates had lower serum apo A-I levels, and they had higher apo B/apo A-I and HDL-C/apo A-I ratios when compared to controls.

CONCLUSION

The lipoprotein profile became more atherogenic in magnesium-exposed neonates as it may be a potential risk factor of cardiovascular heart disease.

Fetal endoscopic surgery: indications and anaesthetic management

Fetal intervention for certain life-threatening conditions has progressed from being primarily experimental in nature to the standard of care in certain circumstances. While surgical techniques have advanced over the past few years, the anaesthetic goals for these interventions have remained the same; namely, minimizing maternal and fetal risk as well as maximizing the chances of a successful fetal intervention and optimize the conditions necessary to carry the fetus to term gestation. Fetal endoscopic techniques allow access to the fetus without the need for a hysterotomy incision, thus improving the chances of controlled post-operative tocolysis and term gestation after fetal intervention. This procedure, however, is not without associated risks to both fetus and mother. This chapter will address the fetal diseases that may benefit from fetoscopic intervention, the rationale behind why maternal and fetal anaesthesia is required, the various anaesthetics used for these cases and specific considerations of both maternal and fetal physiology that aid in the determination of the best anaesthetic technique for individual cases. Methods of intra-operative fetal monitoring and fetal resuscitation will also be discussed.

The effect of intrapartum magnesium sulfate therapy on fetal cardiac troponin I levels at delivery

OBJECTIVE

To determine whether intrapartum magnesium sulfate (MgSO4) therapy for seizure prophylaxis in pre-eclampsia-eclampsia is associated with biochemical evidence of subacute fetal myocardial damage at delivery.

STUDY DESIGN

Troponin I, a cardiac-specific protein used to detect myocardial injury, was measured from the umbilical vein at delivery in term pregnancies complicated by pre-eclampsia and uncomplicated control pregnancies. Women with pre-eclampsia received intravenous MgSO4 as a 6-g load followed by 2 g/hour until delivery. Clinical characteristics and fetal troponin levels were compared between groups.

RESULTS

There was no difference in troponin I concentrations between term patients with intrapartum MgSO4 therapy and controls who did not receive MgSO4 (median 0.86 ng/ml, range 0.72-1.10 vs. 0.89 ng/ml, range 0.68-1.50; p = 1.0). There was also no statistically significant difference in the number of patients with a troponin I level of > or = 1.0 ng/ml between groups (30.8% (4/13) vs. 15.4% (4/26); p = 0.4).

CONCLUSIONS

Our findings suggest that, in term fetuses that are not growth impaired, exposure to intrapartum MgSO4 is not associated with subacute myocardial injury.

Magnesium sulfate as a tocolytic agent

Although magnesium sulfate is widely used as a tocolytic agent in the hope of preventing spontaneous preterm birth, there is a paucity of data from large well-designed randomized clinical studies demonstrating the efficacy of magnesium sulfate therapy. Given the potential for untoward side effects and the inherent risks of magnesium sulfate therapy, a thorough understanding of the potential risks and benefits of this agent is needed. To accomplish this understanding we have provided a detailed review the history, pharmacology, physiology, maternal/fetal side effects, and tocolytic efficacy of magnesium sulfate.