Maternal receipt of magnesium sulfate does not seem to reduce the risk of neonatal white matter damage

Periventricular- intraventricular hemorrhage in the premature infant- A historical perspective

The objective of this chapter is to trace the evolution of intraventricular hemorrhage in the premature infant highlighting the importance of the germinal matrix, a critical role for cerebral blood flow changes in the genesis of hemorrhage, clinical factors that increase the bleeding risk, and potential preventative strategies. In 1976, neuropathological studies demonstrated capillary rupture within the germinal matrix as the precursor of hemorrhage. In 1980, introduction of cranial ultrasound facilitated diagnosis of intraventricular hemorrhage. In 1979, loss of cerebral autoregulation in sick newborn infants was demonstrated. In the 1980's, studies demonstrated the importance of intravascular factors in provoking hemorrhage. In 1983, the association of cerebral blood flow velocity fluctuations and subsequent hemorrhage was demonstrated. In 1994, antenatal steroids use to accelerate lung development was recommended. This was associated with an unanticipated reduction in hemorrhage. In the mid 1990's early indomethacin administration was associated with a reduction of severe hemorrhage.

Risk Factors for Periventricular Leukomalacia in Preterm Infants: A Systematic Review, Meta-analysis, and GRADE-Based Assessment of Certainty of Evidence

BACKGROUND

We analyzed the certainty of evidence (CoE) for risk factors of periventricular leukomalacia (PVL) in preterm neonates, a common morbidity of prematurity.

METHODS

Medline, CENTRAL, Embase, and CINAHL were searched. Cohort and case-control studies and randomised randomized controlled trials were included. Data extraction was performed in duplicate. A random random-effects meta-analysis was utilizedused. CoE was evaluated as per Grading of Recommendations Assessment, Development and Evaluation (GRADE) guidelines.

RESULTS

One hundred eighty-six studies evaluating 95 risk factors for PVL were included. Of the 2,509,507 neonates assessed, 16,569 were diagnosed with PVL. Intraventricular hemorrhage [adjusted odds ratio: 3.22 (2.52-4.12)] had moderate CoE for its association with PVL. Other factors such as hypocarbia, chorioamnionitis, PPROM >48 hour, multifetal pregnancy reduction, antenatal indomethacin, lack of antenatal steroids, perinatal asphyxia, ventilation, shock/hypotension, patent ductus arteriosus requiring surgical ligation, late-onset circulatory collapse, sepsis, necrotizing enterocolitis, and neonatal surgery showed significant association with PVL after adjustment for confounders (CoE: very low to low). Amongst the risk factors associated with mother placental fetal (MPF) triad, there was paucity of literature related to genetic predisposition and defective placentation. Sensitivity analysis revealed that the strength of association between invasive ventilation and PVL decreased over time (P < 0.01), suggesting progress in ventilation strategies. Limited studies had evaluated diffuse PVL.

CONCLUSION

Despite decades of research, our findings indicate that the CoE is low to very low for most of the commonly attributed risk factors of PVL. Future studies should evaluate genetic predisposition and defective placentation in the MPF triad contributing to PVL. Studies evaluating exclusively diffuse PVL are warranted.

Magnesium sulfate use for fetal neuroprotection

PURPOSE OF REVIEW

The aim of this review is to describe the proposed mechanisms of action of magnesium sulfate for fetal neuroprotection, different dosing regimens of the drug that have shown benefit, and to review recent pharmacokinetic studies of the drug to better inform clinicians regarding expected benefits and remaining research questions.

RECENT FINDINGS

Retrospective secondary analysis of the beneficial effects of antenatal magnesium sulfate trial database and prospective pharmacokinetic/pharmacodynamic modeling indicate magnesium sulfate administration for duration longer than 18 h, given within 12 h of delivery, and maintaining a maternal serum level of 4.1 mg/dl may maximize the neuroprotective benefits of the drug.

SUMMARY

Magnesium sulfate in some dosage given before very preterm pregnancy delivery is beneficial for fetal neuroprotection. The exact dose, duration, and timing of administration to maximize this benefit may be more precisely studied using pharmacokinetic/pharmacodynamic modeling techniques before conducting larger randomized trials.

Antenatal magnesium sulphate and adverse neonatal outcomes: A systematic review and meta-analysis

BACKGROUND

There is widespread, increasing use of magnesium sulphate in obstetric practice for pre-eclampsia, eclampsia, and preterm fetal neuroprotection; benefit for preventing preterm labour and birth (tocolysis) is unproven. We conducted a systematic review and meta-analysis to assess whether antenatal magnesium sulphate is associated with unintended adverse neonatal outcomes.

METHODS AND FINDINGS

CINAHL, Cochrane Library, LILACS, MEDLINE, Embase, TOXLINE, and Web of Science, were searched (inceptions to 3 September 2019). Randomised, quasi-randomised, and non-randomised trials, cohort and case-control studies, and case reports assessing antenatal magnesium sulphate for pre-eclampsia, eclampsia, fetal neuroprotection, or tocolysis, compared with placebo/no treatment or a different magnesium sulphate regimen, were included. The primary outcome was perinatal death. Secondary outcomes included pre-specified and non-pre-specified adverse neonatal outcomes. Two reviewers screened 5,890 articles, extracted data, and assessed risk of bias following Cochrane Handbook and RTI Item Bank guidance. For randomised trials, pooled risk ratios (RRs) or mean differences, with 95% confidence intervals (CIs), were calculated using fixed- or random-effects meta-analysis. Non-randomised data were tabulated and narratively summarised. We included 197 studies (40 randomised trials, 138 non-randomised studies, and 19 case reports), of mixed quality. The 40 trials (randomising 19,265 women and their babies) were conducted from 1987 to 2018 across high- (16 trials) and low/middle-income countries (23 trials) (1 mixed). Indications included pre-eclampsia/eclampsia (24 trials), fetal neuroprotection (7 trials), and tocolysis (9 trials); 18 trials compared magnesium sulphate with placebo/no treatment, and 22 compared different regimens. For perinatal death, no clear difference in randomised trials was observed between magnesium sulphate and placebo/no treatment (RR 1.01; 95% CI 0.92 to 1.10; 8 trials, 13,654 babies), nor between regimens. Eleven of 138 non-randomised studies reported on perinatal death. Only 1 cohort (127 babies; moderate to high risk of bias) observed an increased risk of perinatal death with >48 versus ≤48 grams magnesium sulphate exposure for tocolysis. No clear secondary adverse neonatal outcomes were observed in randomised trials, and a very limited number of possible adverse outcomes warranting further consideration were identified in non-randomised studies. Where non-randomised studies observed possible harms, often no or few confounders were controlled for (moderate to high risk of bias), samples were small (200 babies or fewer), and/or results were from subgroup analyses. Limitations include missing data for important outcomes across most studies, heterogeneity of included studies, and inclusion of published data only.

CONCLUSIONS

Our findings do not support clear associations between antenatal magnesium sulphate for beneficial indications and adverse neonatal outcomes. Further large, high-quality studies (prospective cohorts or individual participant data meta-analyses) assessing specific outcomes, or the impact of regimen, pregnancy, or birth characteristics on these outcomes, would further inform safety recommendations. PROSPERO: CRD42013004451.

The complex aetiology of cerebral palsy

Cerebral palsy (CP) is the most prevalent, severe and costly motor disability of childhood. Consequently, CP is a public health priority for prevention, but its aetiology has proved complex. In this Review, we summarize the evidence for a decline in the birth prevalence of CP in some high-income nations, describe the epidemiological evidence for risk factors, such as preterm delivery and fetal growth restriction, genetics, pregnancy infection and other exposures, and discuss the success achieved so far in prevention through the use of magnesium sulfate in preterm labour and therapeutic hypothermia for birth-asphyxiated infants. We also consider the complexities of disentangling prenatal and perinatal influences, and of establishing subtypes of the disorder, with a view to accelerating the translation of evidence into the development of strategies for the prevention of CP.

Fetal Neuroprotection by Magnesium Sulfate: From Translational Research to Clinical Application

Despite improvements in perinatal care, preterm birth still occurs regularly and the associated brain injury and adverse neurological outcomes remain a persistent challenge. Antenatal magnesium sulfate administration is an intervention with demonstrated neuroprotective effects for preterm births before 32 weeks of gestation (WG). Owing to its biological properties, including its action as an N-methyl-d-aspartate receptor blocker and its anti-inflammatory effects, magnesium is a good candidate for neuroprotection. In hypoxia models, including hypoxia-ischemia, inflammation, and excitotoxicity in various species (mice, rats, pigs), magnesium sulfate preconditioning decreased the induced lesions’ sizes and inflammatory cytokine levels, prevented cell death, and improved long-term behavior. In humans, some observational studies have demonstrated reduced risks of cerebral palsy after antenatal magnesium sulfate therapy. Meta-analyses of five randomized controlled trials using magnesium sulfate as a neuroprotectant showed amelioration of cerebral palsy at 2 years. A meta-analysis of individual participant data from these trials showed an equally strong decrease in cerebral palsy and the combined risk of fetal/infant death and cerebral palsy at 2 years. The benefit remained similar regardless of gestational age, cause of prematurity, and total dose received. These data support the use of a minimal dose (e.g., 4 g loading dose ± 1 g/h maintenance dose over 12 h) to avoid potential deleterious effects. Antenatal magnesium sulfate is now recommended by the World Health Organization and many pediatric and obstetrical societies, and it is requisite to maximize its administration among women at risk of preterm delivery before 32 WG.

The ELGAN study of the brain and related disorders in extremely low gestational age newborns

BACKGROUND

Extremely low gestational age newborns (ELGANs) are at increased risk for structural and functional brain abnormalities.

AIM

To identify factors that contribute to brain damage in ELGANs.

STUDY DESIGN

Multi-center cohort study.

SUBJECTS

We enrolled 1506 ELGANs born before 28 weeks gestation at 14 sites; 1201 (80%) survived to 2 years corrected age. Information about exposures and characteristics was collected by maternal interview, from chart review, microbiologic and histological examination of placentas, and measurement of proteins in umbilical cord and early postnatal blood spots.

OUTCOME MEASURES

Indicators of white matter damage, i.e. ventriculomegaly and echolucent lesions, on protocol cranial ultrasound scans; head circumference and developmental outcomes at 24 months adjusted age, i.e., cerebral palsy, mental and motor scales of the Bayley Scales of Infant Development, and a screen for autism spectrum disorders.

RESULTS

ELGAN Study publications thus far provide evidence that the following are associated with ultrasongraphically detected white matter damage, cerebral palsy, or both: preterm delivery attributed to preterm labor, prelabor premature rupture of membranes, or cervical insufficiency; recovery of microorganisms in the placenta parenchyma, including species categorized as human skin microflora; histological evidence of placental inflammation; lower gestational age at delivery; greater neonatal illness severity; severe chronic lung disease; neonatal bacteremia; and necrotizing enterocolitis.

CONCLUSIONS

In addition to supporting a potential role for many previously identified antecedents of brain damage in ELGANs, our study is the first to provide strong evidence that brain damage in extremely preterm infants is associated with microorganisms in placenta parenchyma.

High dose magnesium sulfate exposure induces apoptotic cell death in the developing neonatal mouse brain

BACKGROUND

Magnesium sulfate (MgSO4) is often used as a treatment for pre-eclampsia/eclampsia and preterm labor, resulting in the exposure of a significant number of neonates to this drug despite a lack of evidence suggesting that it is safe, or effective as a tocolytic. While there is evidence that MgSO4 may be neuroprotective in perinatal brain injury, recent reviews have suggested that the effects are dependent upon dose, and that higher doses may actually increase neonatal morbidity and mortality. There is a lack of evidence investigating the neurotoxic effects of neonatal magnesium (Mg) exposure on the developing brain, specifically in terms of neurodevelopmental apoptosis, a cell-killing phenomenon known to be potentiated by other drugs with mechanisms of action at Mg-binding sites (i.e. NMDA receptor antagonists such as MK-801, ketamine, and PCP).

OBJECTIVE

To investigate the effects of Mg exposure on the neonatal mouse brain at different postnatal ages to determine whether MgSO4 treatment causes significant cell death in the developing mouse brain.

METHODS

C57Bl/6 mice were treated with four doses of MgSO4 (250 mg/kg) on postnatal days 3 (P3), 7 (P7) or 14 (P14). Caspase-3 immunohistochemistry, cupric silver staining, and electron microscopy techniques were used to examine Mg-treated brains for neurotoxic effects.

RESULTS

Qualitative evaluation using cupric silver staining revealed widespread damage throughout the brain in P7 animals. Results of electron microscopy confirmed that the cell death process was apoptotic in nature. Quantitative evaluation of damage to the cortex, caudate-putamen, hippocampus, thalamus, and cerebellum showed that Mg treatment caused significant brain damage in animals treated on P3 and P7, but not P14.

CONCLUSIONS

Administration of high doses of Mg may be detrimental to the fetal brain, particularly if exposure occurs during critical periods of neurodevelopment.

Neuroprotective effect of long-term MgSO4 administration after cerebral hypoxia-ischemia in newborn rats is related to the severity of brain damage

Previous studies have shown contradictory results regarding magnesium-mediated neuroprotection in animal models of perinatal asphyxia. The aim of this study is to investigate the effects of MgSO(4) postasphyxial treatment on hypoxia-ischemia (HI)-induced brain injury in neonatal rats and the possibility that this effect is related to the severity of brain damage. Seven-day-old rats underwent unilateral carotid artery ligation followed by 1 or 2 hours of hypoxia (8% O(2)) and MgSO(4) administration. Adenosine triphosphate/phosphocreatine and glutamate/glutamine measurements and neuropathological evaluation of the hippocampus were used to assess the effects of HI and MgSO(4). HI caused time-dependent changes in energy stores, amino acid concentrations, and brain damage. Administration of MgSO(4) after 1 hour but not after 2 hours of hypoxia resulted in significant prevention of HI-induced brain injury. MgSO(4) administration results in a significant protection against moderate HI-induced brain damage, whereas it fails to offer a similar effect against severe brain damage.

Verbal and memory skills in males with Duchenne muscular dystrophy

Duchenne muscular dystrophy (DMD) is a progressive pediatric disorder that affects both muscle and brain. Children with DMD have mean IQ scores that are about one standard deviation lower than population means, with lower Verbal IQ than Performance IQ scores. For the present study, verbal skills and verbal memory skills were examined in males with DMD with the Clinical Evaluation of Language Fundamentals, 3rd edition, and the California Verbal Learning Test for Children. Performance of 50 males with DMD (age range 6-14 y, mean 9 y 4 mo [SD 2 y 1 mo]) was compared to normative values. Two subsets of the probands were also compared with two comparison groups: unaffected siblings (n=24; DMD group age range 6-12 y, mean 9 y 1 mo [SD 1 y 8 mo]; sibling age range 6-15 y, mean 9 y 11 mo [SD 2 y 4 mo]) and males with cerebral palsy (CP); (n=23; DMD group age range 6-9 y, mean 7 y 8 mo [SD 1 y 2 mo]; CP age range 6-8 y, mean 6 y 8 mo [SD 0 y 8 mo]). Results demonstrated that although males with DMD performed slightly more poorly than normative values, they performed comparably to the controls on most measures. Consistent deficits were observed only on tests requiring immediate repetition for verbal material (Recalling Sentences, and Concepts and Directions). On other language tasks, including tests of understanding and use of grammar, and understanding of semantic relationships, the males with DMD performed well. Moreover, the males with DMD performed well on multiple indices of verbal recall, and there was no evidence of declarative memory deficits. DMD is a single-gene disorder that is selectively associated with decreased verbal span capacity, but not impaired recall.

Social behavior problems in boys with Duchenne muscular dystrophy

Duchenne muscular dystrophy (DMD) is a chronic, progressive pediatric disease that affects both muscle and brain. The objectives of the study were to examine parent reported behavior in children with DMD, investigate the influence of chronic illness, intellectual ability and etiology on behavior, and determine whether a specific behavioral profile is associated with DMD. Parental ratings of boys with DMD (n = 181) on the Child Behavior Checklist behavior scales were examined and compared to reported findings of children with other chronic illnesses, unaffected siblings of boys with DMD (n = 86), and children with cerebral palsy (CP) (n = 42). Increased ratings of general behavior problems were reported, and neither physical progression nor intellectual level contributed to behavioral ratings. Among the children with DMD, the Social Problem behavior scale had the greatest number of "clinically significant" ratings (34%). Between-group comparisons showed significantly more boys with DMD were rated as having social behavior problems than either the sibling or CP comparison groups. In addition to the increase in reported behavioral problems likely related to the effects of chronic illness, boys with DMD may be at heightened risk for specific social behavior problems. The specificity of the findings of the behavior profile in DMD may be partially due to the lack of dystrophin isoforms in the central nervous system, and not solely a reactive response to the illness.

Risk factors and clinical outcomes of pulmonary interstitial emphysema in extremely low birth weight infants

OBJECTIVE

We studied the ante- and postnatal risk factors and clinical outcomes associated with pulmonary interstitial emphysema (PIE) in extremely low birth weight infants (ELBW, <1000 g at birth) in the present era of tocolytics, antenatal steroid and postnatal surfactant administration.

STUDY DESIGN

This was a retrospective case-controlled study of all ELBW admitted consecutively during a designated study-period in a level III nursery. Data were analyzed by performing univariate and multivariate analysis as applicable.

RESULTS

Infants with PIE had lower 1 and 5 min Apgar scores (P=0.04 and 0.003 respectively), increased surfactant utilization (P=0.004), higher maximum inspired oxygen concentration (P=0.04) and mean airway pressure administration (P=0.02) during the first week of life, and increased neonatal mortality (P=0.01). They received higher antenatal doses of magnesium sulfate (MgSO(4)) (P=0.02). 56% of infants with PIE were exposed to more than 10 g of MgSO(4) (Mg10), compared to 15% in non-PIE group (P=0.01). The multivariate logistic regression analysis including significant co-variates revealed an independent association between Mg10 and PIE (P=0.01, Odds ratio 19.8, 95% CI 1.5-263).

CONCLUSION

Pulmonary interstitial emphysema is associated with increased mortality in ELBW infants. Mg10 is an independent risk factor for PIE in this population.

Neonatal color Doppler US study: normal values of cerebral blood flow velocities in preterm infants in the first month of life

The aim of this study is to generate normal reference values of cerebral blood flow velocities (CBFV) and Doppler indices (DI) in the anterior (ACA) and the middle (MCA) cerebral arteries during the first month of life in "healthy" preterm infants. CBFV were obtained with color Doppler technique in seventy selected preterm infants divided in four groups of gestational age (GA) (25 to 28; 29 to 30; 31 to 32; 33 to 35 wk). Our data demonstrate that CBFV increase with rising GA, birth weight (BW) and postnatal age. Additionally, we can provide the median values, tenth and ninetieth percentiles of CBFV and DI, in the ACA and MCA in each GA group as reference normal values of CBFV and DI in preterm newborn.

Oxygen and glucose deprivation induces major dysfunction in the somatosensory cortex of the newborn rat

The mechanisms and functional consequences of ischemia-induced injury during perinatal development are poorly understood. Subplate neurons (SPn) play a central role in early cortical development and a pathophysiological impairment of these neurons may have long-term detrimental effects on cortical function. The acute and long-term consequences of combined oxygen and glucose deprivation (OGD) were investigated in SPn and compared with OGD-induced dysfunction of immature layer V pyramidal cortical neurons (PCn) in somatosensory cortical slices from postnatal day (P)0-4 rats. OGD for 50 min followed by a 10-24-h period of normal oxygenation and glucose supply in vitro or in culture led to pronounced caspase-3-dependent apoptotic cell death in all cortical layers. Whole-cell patch-clamp recordings revealed that the majority of SPn and PCn responded to OGD with an initial long-lasting ischemic hyperpolarization accompanied by a decrease in input resistance (R(in)), followed by an ischemic depolarization (ID). Upon reoxygenation and glucose supply, the recovery of the membrane potential and R(in) was followed by a Na+/K+-ATPase-dependent postischemic hyperpolarization, and in almost half of the investigated SPn and PCn by a postischemic depolarization. Whereas neither a moderate (2.5 mm) nor a high (4.8 mm) increase in extracellular magnesium concentration protected the SPn from OGD-induced dysfunction, blockade of NMDA receptors with MK-801 led to a significant delay and decrease of the ID. Our data demonstrate that OGD induces apoptosis and a profound dysfunction in SPn and PCn, and underline the critical role of NMDA receptors in early ischemia-induced neuronal damage.

Brain lesions in newborns exposed to high-dose magnesium sulfate during preterm labor

High-dosage, tocolytic magnesium sulfate (MgSO4) administered to pregnant women during preterm labor can be toxic, and sometimes lethal, for their newborns (Cochrane Database of Systematic Reviews (relative mortality risk 2.82, 95% confidence interval 1.2-6.6)). Based on the results of the Magnesium and Neurologic Endpoints Trial and the work of many others, a unifying triangular concept is proposed to account for the increased prevalence of brain lesions, with their likely resultant mortality, in neonates and infants exposed to high-dose MgSO4 in the context of preterm labor. We review the evidence that: (1) elevated circulating levels of serum ionized magnesium occurring in mothers, and therefore in their babies, at the time of delivery are associated with subsequent neonatal intraventricular hemorrhage (IVH); (2) neonatal IVH is strongly associated with lenticulostriate vasculopathy (LSV), an unusual mineralizing lesion involving the thalami and basal ganglia of the neonate; and, (3) exposure to 50 g or more of tocolytic MgSO4 during preterm labor is associated with the development of LSV.

Antenatal Glucocorticoids Increase Early Total Thyroxine Levels in Premature Infants

BACKGROUND

Hypothyroxinemia is associated with adverse neonatal outcomes including white matter damage, cerebral palsy, poor neurodevelopment and death. It has become increasingly important to understand the natural history and modifiers of thyroid function in the premature infant. It is standard obstetrical practice to offer antenatal glucocorticoids to pregnant women with threatened preterm delivery. Few studies have investigated the effect of antenatal glucocorticoids on neonatal thyroid function.

OBJECTIVE

To examine the association between antenatal exposure to glucocorticoids and early total thyroxine (T4) levels among extremely premature infants.

METHODS

We studied 521 infants born at 4 medical centers. Entry criteria included a gestational age of 23-28 weeks and a serum thyroxine level obtained in the first postnatal week. Receipt of antenatal glucocorticoids was recorded as none, partial, or complete. A complete course consisted of two doses of betamethasone or four doses of dexamethasone within a 48-hour period between 2 and 7 days of delivery. Early total T4 levels were obtained from state-mandated newborn screening programs.

RESULTS

Controlling for potential maternal, perinatal and neonatal confounding variables, infants exposed to a complete course of antenatal glucocorticoids had total T4 levels 0.8 microg/dl higher than their peers who were not exposed to a complete course of antenatal glucocorticoids (p = 0.03).

CONCLUSIONS

Extremely premature infants who received a complete course of antenatal glucocorticoids had significantly higher total thyroxine levels in the first postnatal week. Maternal, perinatal, and early neonatal variables did not completely explain this association. We speculate that antenatal glucocorticoids influence early neonatal thyroid function.

The combined maternal administration of magnesium sulfate and aminophylline reduces intraventricular hemorrhage in very preterm neonates

OBJECTIVE

To determine whether the adjunctive administration of aminophylline and magnesium sulfate to mothers at risk for preterm birth can reduce the rate of intraventricular hemorrhage in neonates born at less than 30 weeks of gestation.

STUDY DESIGN

A prospective study was conducted to determine whether the rate of intraventricular hemorrhage was different in patients at risk for preterm delivery treated with ritodrine, magnesium sulfate, aminophylline, and corticosteroids (group A) versus patients treated with ritodrine and corticosteroids (group B). During the study period (January 1996 to December 2001), 125 patients enrolled in the study. Treatment was assigned by alternative allocation, and the study was designed to compare the rate of intraventricular hemorrhage in neonates born before the 30th week of gestation (primary outcome), 78 newborns in group A and 68 in group B. The proportion of neonates with intraventricular hemorrhage was calculated, and data were analyzed with Student t test, chi 2 , and logistic regression analysis.

RESULTS

The frequency of severe respiratory distress syndrome needing surfactant replacement and high-pressure positive ventilation, patent ductus arteriosus, and retinopathy of prematurity was not different between the 2 groups. However, the rate of intraventricular hemorrhage was lower in neonates born before 30 weeks whose mothers received adjunctive aminophylline and magnesium sulphate (group A) than in the group that did not receive these 2 agents (group B). The overall frequency of intraventricular hemorrhage was 5.1% (4/78) versus 20.6% (14/68) ( P < .001), and the frequency of intraventricular hemorrhage grade 3-4 was 1.3% (1/78) versus 10.3 % (7/68; P < .001), respectively.

CONCLUSION

Adjunctive maternal administration of aminophylline and magnesium sulfate was associated with a significant reduction in the rate of intraventricular hemorrhage in neonates born before 30 completed weeks.

Antenatal risk factors associated with the development of lenticulostriate vasculopathy (LSV) in neonates

OBJECTIVE

To determine the antenatal risk factors associated with neonatal lenticulostriate vasculopathy (LSV).

STUDY DESIGN

Women in preterm labor were randomized to magnesium sulfate (MgSO4), other tocolytic, or saline control. The surviving babies underwent head ultrasounds (HUS) (weeks of life 1, 2, and 4) and periodic developmental examinations (months 4, 8, 12, and 18).

RESULTS

Of 140 infants, 17.1% (24) had neonatal intraventricular hemorrhage (IVH), and 10.0% (14) had LSV (half of the latter (7 of 14) had both IVH and LSV). In a regression model in which other risk factors were controlled for, the association between antenatal exposures to tocolytic MgSO4 >or=50 g and LSV were significant (adjusted odds ratio (OR), 8.3; 95% confidence interval (CI), 1.5 to 45.0; p=0.01).

CONCLUSION

Based on our data and their analyses, we infer that antenatal exposure to high-dosage, tocolytic MgSO4 may be associated with LSV.

The effects of systemic magnesium sulfate infusion on brain magnesium concentrations and energy state during hypoxia-ischemia in newborn miniswine

The mechanism of neuroprotection associated with systemically administered magnesium remains unclear. This investigation examined the acute effects of systemically administered MgSO4 on brain extracellular ([Mg]ecf) and intracellular ([Mg]i) fluid Mg concentrations, specific brain phosphorylated metabolites, and brain intracellular pH. Miniswine were studied with P-31 magnetic resonance spectra, to derive [Mg]i, and brain microdialysis probes, to measure [Mg]ecf. Animals were infused with MgSO4 (n = 5, 275 mg/kg over 30 min followed by 100 mg/kg over 30 min, designated MgHI) or Na2SO4 (n = 5, designated NaHI), and both groups underwent hypoxia-ischemia (HI) over the last 15 min of the infusions. Groups differed in plasma [Mg] at the completion of HI (9.1 +/- 1.5 versus 1.1 +/- 0.6 mM for MgHI and NaHI, respectively, p < 0.05). MgHI had elevations of [Mg]ecf (0.23 +/- 0.11 and 0.40 +/- 0.14 mM at control and completion of HI, respectively), and [Mg]ecf was unchanged for NaHI (p < 0.05 versus MgHI). At the completion of HI, MgHI had greater decreases in nucleoside triphosphate (NTP) (48 +/- 6% of control), and more brain acidosis after HI (6.01 +/- 0.07) compared with NaHI (NTP, 70 +/- 3% of control; brain pH, 6.51 +/- 0.14, both p < 0.05 versus MgHI). [Mg]i increased to elevated values during HI in both MgHI and NaHI (p < 0.05 versus control of each group) and remained higher in MgHI over the next 25 min (p < 0.05 versus NaHI). There were inverse correlations during HI between [Mg]i and brain NTP (r2 = 0.73 and 0.59 for MgHI and NaHI, respectively), and brain acidosis (r2 = 0.85 and 0.85 for MgHI and NaHI, respectively) in each group. These findings indicate complex effects of Mg on the brain. Elevation of [Mg]ecf may be beneficial with regards to excitatory neurotransmitters. However, greater disturbance of brain NTP concentration, more acidosis, and the increase in [Mg]i may offset any benefit. The results warrant further investigation using indicators of neuronal injury to determine whether Mg supplementation provides neuroprotection.

Labor and delivery factors in brain damage, disabling cerebral palsy, and neonatal death in low-birth-weight infants

OBJECTIVE

We assessed the relationships between active labor and neonatal death, neonatal brain damage, and disabling cerebral palsy in low-birth-weight infants.

STUDY DESIGN

A population-based cohort of 961 infants with birth weights of 580 to 2000 g and gestational ages >or=26 completed weeks. Neonatal brain damage was assessed by ultrasound scanning in the first weeks of life; disabling cerebral palsy was assessed at 2 years of age (corrected for gestational age).

RESULTS

After being controlled for possible confounders, active labor was associated significantly with an increased risk of parenchymal echodensities/lucencies and/or ventricular enlargement (odds ratio, 2.3; 95% CI, 1.2-4.5) but not with germinal matrix/intraventricular hemorrhage (odds ratio, 1.3; 95% CI, 0.8-2.1), neonatal death (odds ratio, 1.8; 95% CI, 0.8-4.0), or disabling cerebral palsy (odds ratio, 1.6; 95% CI, 0.7-3.7). In vertex presentations only, active labor was associated with a nearly 4-fold increase in risk of neonatal death (odds ratio, 3.8; 95% CI, 1.3-10.9). In nonvertex presentations only, active labor was associated strongly with parenchymal echodensities/lucencies and/or ventricular enlargement (odds ratio, 4.3; 95% CI, 1.2-15.6) and disabling cerebral palsy (odds ratio, 8.2; 95% CI, 1.4-49.9).

CONCLUSION

The only adverse outcome that was associated consistently with active labor was parenchymal echodensities/lucencies and/or ventricular enlargement. Fetal presentation modified the relationships between active labor and adverse outcomes. Delivery mode (whether vaginal or cesarean delivery) was not associated with any of the outcomes that were evaluated.

A comparison of breastfed children with nutritional rickets who present during and after the first year of life

This study compares the patient characteristics of breastfed children in Baltimore, Maryland from 1990 to 2000 diagnosed with nutritional rickets at 12 months or younger to those older than 12 months to gain a better understanding of nutritional and environmental factors. All 30 of the patients were African American. Patients 12 months or younger (n=15) compared to those older than 12 months (n=15) were more likely to be born during the summer and to present with seizures and hypocalcemia. We recommend vitamin D supplementation of all breastfed infants at an early age and that supplementation continue throughout the duration of breastfeeding.

Initiation of breastfeeding among mothers of very low birth weight infants

OBJECTIVE

To examine factors that predict the initiation of expressed milk feedings and the transition to direct breastfeedings among mothers of very low birth weight (VLBW) infants.

METHODS

The sample consists of 361 mother-infant pairs enrolled in a follow-up study of children aged 6 to 8 years who were born weighing <1501 g in 1 of 5 hospitals between 1991-1993. Chart review at birth provided data on neonatal characteristics and demographic factors at delivery were obtained by postpartum maternal interview. Information regarding infant feeding practices was obtained at follow-up.

RESULTS

In this study, 60% of mothers initiated expressed milk feedings for their VLBW infants. However, the duration of these feedings was brief with 52% of infants receiving 1 to 3 months or less of human milk feedings. Greater educational attainment, private insurance, and breastfeeding experience were each independently associated with the decision to provide expressed milk feedings. Only 27% of mothers reported directly breastfeeding their VLBW infants. The transition from expressed milk feedings to direct breastfeedings was positively associated with sociodemographic factors including maternal age, insurance status, and breastfeeding experience as well as the length of hospitalization, an indicator of infant health.

CONCLUSIONS

Sociodemographic factors were associated with both the decision to initiate expressed milk feedings and the transition to direct breastfeedings. However, factors relating to infant health only influenced the transition to direct breastfeedings. Intervention programs need to consider the sociodemographic factors that influence infant feeding decisions as well as specific challenges encountered by mothers of VLBW infants.

Parental stress in mothers of boys with duchenne muscular dystrophy

OBJECTIVE

To examine parental stress in mothers of boys with Duchenne muscular dystrophy (DMD).

METHOD

Stress and its predictors were examined in mothers of boys with DMD (n = 112). Comparisons were made with mothers of healthy children (n = 800), children with cerebral palsy (CP; n = 28), siblings of boys with DMD (n = 46), and longitudinally (n = 16).

RESULTS

The presence of problem child behaviors consistently predicted maternal stress. Stress related to child behavior was higher in the DMD versus the normative group. No differences in stress were found in the DMD versus CP groups. Stress related to boys with DMD versus siblings was not significantly different. Over time, maternal stress related to child variables diminished.

CONCLUSION

Stress in mothers of boys with DMD is elevated, possibly due to increased problem behaviors, particularly in social interactions, rather than due to the physical demands of the disease alone.

Hemorrhagic-ischemic cerebral injury in the preterm infant: current concepts

PV-IVH and adjacent white matter injury remains a significant problem in the premature infant. The potential mechanisms contributing to injury are complex and involve factors related to blood flow and its regulation, as well as cellular mediators including cytokines, free radical formation, and excitotoxin release. Although a reduction in the occurrence of severe IVH can be achieved with indomethacin, it does translate into long-term neurodevelopmental benefit. This reinforces the concept of a more diffuse injury to brain in sick premature infants than is apparent from the appearance of current neuroimaging techniques.

Periventricular leukomalacia, inflammation and white matter lesions within the developing nervous system

Periventricular leukomalacia (PVL) occurring in premature infants, represents a major precursor for neurological and intellectual impairment, and cerebral palsy in later life. The disorder is characterized by multifocal areas of necrosis found deep in the cortical white matter, which are often symmetrical and occur adjacent to the lateral ventricles. There is no known cure for PVL. Factors predisposing to PVL include birth trauma, asphyxia and respiratory failure, cardiopulmonary defects, premature birth/low birthweight, associated immature cerebrovascular development and lack of appropriate autoregulation of cerebral blood flow in response to hypoxic-ischemic insults. The intrinsic vulnerability of oligodendrocyte precursors is considered as central to the pathogenesis of PVL. These cells are susceptible to a variety of injurious stimuli including free radicals and excitotoxicity induced by hypoxic-ischemic injury (resulting from cerebral hypoperfusion), lack of trophic stimuli, as well as secondary associated events involving microglial and astrocytic activation and the release of pro-inflammatory cytokines TNF-alpha and IL-6. It is yet unclear whether activated astrocytes and microglia act as principal participants in the development of PVL lesions, or whether they are representatives of an incidental pathological response directed towards repair of tissue injury in PVL. Nevertheless, the accumulated evidence points to a pathological contribution of microglia towards damage. The topography of lesions in PVL most likely reflects a combination of the relatively immature cerebrovasculature together with a failure in perfusion and/or hypoxia during the greatest period of vulnerability occurring around mid-to-late gestation. Mechanisms underlying the pathogenesis of PVL have so far been related to prenatal ischemic injury to the brain initiated within the third trimester, which result in global cognitive and developmental delay and motor disturbances. Over the past few years, several epidemiological and experimental studies have implicated intrauterine infection and chorioamnionitis as causative in the pathogenesis of PVL. In particular, recent investigations have shown that inflammatory responses in the fetus and neonate can contribute towards neonatal brain injury and development-related disabilities including cerebral palsy. This review presents current concepts on the pathogenesis of PVL and emphasizes the increasing evidence for an inflammatory pathogenic component to this disorder, either resulting from hypoxic-ischemic injury or from infection. These findings provide the basis for clinical approaches targeted at protecting the premature brain from inflammatory damage, which may prove beneficial for treating PVL, if identified early in pathogenesis.

Association between the use of antenatal magnesium sulfate in preterm labor and adverse health outcomes in infants

OBJECTIVE

The purpose of this study was to determine whether the use of antenatal magnesium sulfate prevents adverse outcomes (neonatal intraventricular hemorrhage, periventricular leucomalacia, death, and cerebral palsy).

STUDY DESIGN

In a controlled trial, we randomized mothers in preterm labor to magnesium sulfate, "other" tocolytic, or placebo. At delivery, umbilical cord blood was collected for the later determination of serum ionized magnesium levels. Neonatal cranial ultrasound scans were obtained periodically for the diagnosis of intraventricular hemorrhage and periventricular leucomalacia. Among survivors, the diagnosis of cerebral palsy was made at age 18 months.

RESULTS

Children with adverse outcomes had higher umbilical cord magnesium levels at delivery. In regression models that controlled for confounders, which included very low birth weight, magnesium remained a significant risk factor (adjusted odds ratio, 3.7; 95% CI, 1.1-11.9; P =.03).

CONCLUSION

Contrary to original hypotheses, this randomized trial found that the use of antenatal magnesium sulfate was associated with worse, not better, perinatal outcome in a dose-response fashion.

Association between maternal serum ionized magnesium levels at delivery and neonatal intraventricular hemorrhage

OBJECTIVES

To determine whether magnesium sulfate (MgSO(4)) exposure is associated with a reduced risk for neonatal intraventricular hemorrhage (IVH).

STUDY DESIGN

In a randomized, controlled trial, women in preterm labor were randomly assigned to receive MgSO(4), "other" tocolytic, or saline control. At delivery, we collected maternal antecubital and umbilical cord blood for determination of serum ionized magnesium levels. Neonatal IVH was diagnosed by cranial ultrasonogram.

RESULTS

Among 144 infants, 24 were diagnosed with IVH. Using crude intention-to-treat analysis, we found that 18% (13/74) of survivors exposed after birth to MgSO(4) had IVH compared with 16% (11/70) of babies who were not exposed. Infants who had IVH were more likely to have been delivered by mothers with higher serum ionized magnesium (Mg) levels (0.75 vs 0.56 mmol/L) (P =.01). Using multivariable logistic regression, we confirmed that higher Mg levels are a significant predictor of neonatal IVH (adjusted odds ratio, 15.8; 95% CI, 1.4-175.0) even when adjusted for birth weight, gestational age, antenatal hemorrhage, and neonatal glucocorticoid exposure.

CONCLUSIONS

In mothers with preterm labor, our data indicate that antenatal MgSO(4) exposure may be associated with an increased risk for IVH among their newborns.

Risk of cranial ultrasound abnormalities in very-low-birth-weight infants conceived with assisted reproductive techniques

OBJECTIVE

To evaluate risks of cranial ultrasound abnormalities among very-low-birth-weight (VLBW) infants conceived with fertility therapy (ovulation induction only or with assisted reproductive techniques [ART]) and of multiple gestation pregnancies.

STUDY DESIGN

The incidences of cranial ultrasound abnormalities in 1473 VLBW infants conceived with and without fertility therapy and born of multiple versus singleton pregnancies were compared, using logistic regression models.

RESULTS

Infants conceived with ART were less likely to have intraventricular hemorrhage (IVH). Twins and triplets had risks of cranial ultrasound abnormalities similar to those of singletons. Twins and triplets conceived with ART were at lower risk of IVH.

CONCLUSION

VLBW infants conceived with ART do not appear to be at increased risk of cranial ultrasound abnormalities. Likewise, twins and triplets were not at increased risk of these abnormalities.

Growth-restricted premature infants are at increased risk for low thyroxine

OBJECTIVE

To evaluate, in extremely premature infants, the relationship between growth restriction and early total thyroxine levels, and to determine how maternal, prenatal, perinatal and neonatal variables influence the relationship.

STUDY DESIGN

719 infants born at four medical centers in Massachusetts, New York and New Jersey between 1991 and 1993 were studied. Entry criteria included: gestational age 23--30 weeks, birth weight 500--1500 g, and a serum thyroxine level obtained in the first week of life. Infants born to mothers with a history of thyroid disease were excluded. Birth weight and total thyroxine level are expressed as z-scores (standard deviation units) to adjust for their relationship to gestational age.

RESULTS

In linear regression analysis, there was a 0.18 decrease in the total thyroxine z-score for each 1.0 (1 standard deviation unit) decrease in birth weight z-score (p=0.0001). Adjustment for multiple potential maternal, prenatal, perinatal and neonatal confounders failed to identify a factor or factors that could account for the observed association.

CONCLUSIONS

The early total thyroxine level in extremely preterm infants was significantly associated with birth weight z-score. This relationship persisted even after adjustment for maternal, prenatal, perinatal and neonatal confounders suggesting antenatal influences. Of clinical importance, growth-restricted infants are at increased risk for early hypothyroxinemia and, possibly, to its related morbidities.

Effect of maternal tocolysis on the incidence of severe periventricular/intraventricular haemorrhage in very low birthweight infants

AIM

To examine the relation between grade III-IV periventricular/intraventricular haemorrhage (PVH/IVH) and antenatal exposure to tocolytic treatment in very low birthweight (VLBW) premature infants.

STUDY DESIGN

The study population consisted of 2794 infants from the Israel National VLBW Infant Database, of gestational age 24-32 weeks, who had a cranial ultrasound examination during the first 28 days of life. Infants of mothers with pregnancy induced hypertension or those exposed to more than one tocolytic drug were excluded. Of the 2794 infants, 2013 (72%) had not been exposed to tocolysis and 781 (28%) had been exposed to a single tocolytic agent. To evaluate the effect of tocolysis and confounding variables on grade III-IV PVH/IVH, the chi(2) test, univariate analysis, and a logistic regression model were used.

RESULTS

Of the 781 infants (28%) exposed to tocolysis, 341 (12.2%) were exposed to magnesium sulphate, 263 (9.4%) to ritodrine, and 177 (6.3%) to indomethacin. The overall incidence of grade III-IV PVH/IVH was 13.4%. In the multivariate logistic regression analysis, the following factors were related significantly and independently to grade III-IV PVH/IVH: no prenatal steroid treatment, low gestational age, one minute Apgar score 0-3, respiratory distress syndrome, patent ductus arteriosus, mechanical ventilation, and pneumothorax. Infants exposed to ritodrine tocolysis (but not to the other tocolytic drugs) were at significantly lower risk of grade III-IV PVH/IVH after adjustment for other variables (odds ratio = 0.3; 95% confidence interval 0.2 to 0.6).

CONCLUSION

This study suggests that antenatal exposure of VLBW infants to ritodrine tocolysis, in contrast with tocolysis induced by magnesium sulphate or indomethacin, was associated with a lower incidence of grade III-IV PVH/IVH.

Advances in prevention and treatment of cerebral palsy

In recent years there have been a number of advances in understanding of predisposing and protective factors in the development of cerebral palsy in infants. Multiple gestation births, maternal infection, and maternal and fetal thrombophilic conditions all predispose to the development of CP in the infant. Opportunities for prevention of CP may develop from an improved understanding of these factors and their mechanisms of operation. Similar progress has been made in the evaluation of treatments for CP and the effects of these treatments on the individual's impairment, function, and disability. Selective posterior rhizotomy and Botulinum toxin A are now widely used in the treatment of spasticity. The challenge remains to determine how effectively these promising interventions can alter long-term function and quality of life outcomes in children and adults with CP.

Perinatal brain injury: from pathogenesis to neuroprotection

Brain injury secondary to hypoxic-ischemic disease is the predominant form of all brain injury encountered in the perinatal period. The focus of this article is the most recent research developments in this field and especially those developments that should lead to the most profound effects on interventions in the first years of the new millennium. Neuronal injury is the predominant form of cellular injury in the term infant. The principal mechanisms leading to neuronal death after hypoxia-ischemia/reperfusion are initiated by energy depletion, accumulation of extracellular glutamate, and activation of glutamate receptors. The cascade of events that follows involves accumulation of cytosolic calcium and activation of a variety of calcium-mediated deleterious events. Notably this deleterious cascade, which evolves over many hours, may be interrupted even if interventions are instituted after termination of the insult, an important clinical point. Of the potential interventions, the leading candidates for application to the human infant in the relative short-term are mild hypothermia, inhibitors of free radical production, and free radical scavengers. Promising clinical data are available for the use of mild hypothermia.

Risk factors for neurologic impairment among very low-birth-weight infants

Although cerebral palsy is the most common neurologic impairment among very low-birth-weight survivors, its etiology remains uncertain. Current research supports the role of both antenatal and neonatal factors in the pathogenesis of cerebral palsy among these extremely premature infants. Important antenatal risk factors include chorioamnionitis and multiple placental lesions. Maternal preeclampsia may provide neuroprotection. The major neonatal risk factors include severe cranial ultrasound abnormalities, chronic lung disease, hyperbilirubinemia, and possibly hypothyroxinemia.

Intraventricular haemorrhage and posthaemorrhagic hydrocephalus: pathogenesis, prevention and future interventions

Intraventricular haemorrhage (IVH) is still a major complication of preterm birth with serious disability resulting. The fragile blood vessels in the germinal matrix below the ventricular lining and the instability of blood flow to this highly vascular area are the main mechanisms behind IVH. There is good evidence that corticosteroid therapy before preterm delivery reduces mortality and IVH substantially with a trend towards a reduction in disability. There is good evidence that postnatal indomethacin reduces IVH but no evidence that mortality or disability is reduced. There is evidence that stabilizing cerebral blood flow with pancuronium in infants with respiratory distress reduces IVH in the minority of infants with marked fluctuations. There is limited evidence that postnatal vitamin E and ethamsylate reduce IVH but insufficient evidence of reduced mortality or disability. Hydrocephalus following IVH results initially from multiple small blood clots throughout the CSF channels impeding circulation and re-absorption. Transforming growth factor beta is released into the CSF and there is mounting evidence that this cytokine stimulates the laying down of extracellular matrix proteins such as laminin and fibronectin which produce permanent obstruction to the CSF pathways. Interventions such as early lumbar punctures, diuretic drugs to reduce CSF production and intraventricular fibrinolytic therapy have been tested and, not only fail to prevent shunt dependence, death or disability, but have significant adverse effects. Surgical interventions such as subcutaneous reservoir and external drain have not been subject to controlled trial. Ventriculoperitoneal shunt is not feasible in the early phase after IVH but, despite the problems with blockages and infections, remains the only option for infants with excessive head expansion over periods of weeks. New treatment approaches aimed at preventing hydrocephalus are needed.

Antenatal therapies and the developing brain

This chapter presents a review of basic science and human studies of two commonly used pharmacologic agents (antenatal steroids and magnesium sulfate), in pregnancies at risk of preterm delivery, and examines the effects of these therapies on the developing brain. Very low birthweight (VLBW) infants are known to be at risk of both short-term and long-term neurodevelopmental sequelae; therefore, an understanding of the mechanisms contributing to both neuroprotective and neurotoxic effects of antenatal therapies on the immature brain and potential effects on long-term outcome are critical. Although the short-term beneficial effects of a single course of antenatal steroids are well documented, the experimental animal literature suggests detrimental effects on neurodevelopment of multiple doses. In addition, clinical studies of repeat doses suggest a negative impact on head and brain growth. The animal and human data on the effects of MgSO(4)are also mixed with both beneficial effects or no effects on neurodevelopment. This review will discuss the potential impact of single versus multiple doses and timing of doses on the brain.

Hypocarbia during the first 24 postnatal hours and white matter echolucencies in newborns < or = 28 weeks gestation

The purpose of the present study was to test the hypothesis that newborns < or = 28 wk gestation who have a PCO(2) measurement in the lowest gestational age-specific quartile (hypocarbia) on the first day of life are not at increased risk for ultrasonographic white matter echolucency (EL) after adjustment for confounders. The sample consisted of 799 infants < or = 28 wk gestation born during 1991-1993. Forty-eight infants with EL were classified as cases and compared with 751 controls, i.e. those without EL. We performed univariable comparisons, stratified analyses, and multivariable logistic regression. In the univariable analyses, hypocarbia on the first day of life was associated with an increased EL risk. The odds ratios for the hypocarbia-EL relationship were prominently elevated in the strata of infants who did not have other major risk factors for EL (e.g. gestational age 26-28 wk, normothyroxinemia, no characteristics of antenatal infection). In the multivariable analyses, the association diminished after adjustment with a hypocarbia propensity score (odds ratio = 1.7; 95 % confidence interval, 0.8-3.2) or with potential confounders.

Long-term magnesium sulfate treatment as protection against hypoxic-ischemic brain injury in seven-day-old rats

OBJECTIVE

Our purpose was to study the effects of long-term treatment with magnesium sulfate on hypoxic-ischemic brain damage in newborn rats.

STUDY DESIGN

Seven-day-old rat pups (n = 120) were exposed to unilateral carotid artery ligation and 2 hours of hypoxia (8% oxygen in 92% nitrogen). Neuronal loss was evaluated in 4 groups. The loading dose group (n = 25) received a bolus injection of 270 mg/kg magnesium sulfate intraperitoneally. The maintenance group (n = 26) received 3 days of continuous infusion of magnesium sulfate with a micro-osmotic pump at a rate of 72 mg/kg per hour. The loading dose-plus-maintenance group (n = 23) received both. The control group (n = 46) did not receive magnesium. Seven days after the injury the pups were killed and the brains were removed for analysis. Severity of neuronal loss was evaluated in the cerebral cortex and hippocampus and compared among groups by chi2 test.

RESULTS

Cyst formation resulting from necrosis was significantly decreased in the maintenance group (15%) and loading dose-plus-maintenance group (9%) but not in the loading dose group (52%) relative to the control group (46%). Severity of neuronal loss in the cerebral cortex and the hippocampus was also significantly improved in the maintenance group and the loading dose-plus-maintenance group but not in the loading dose group. Mortality rates were not different among the groups. Magnesium ion concentrations at 24 hours were significantly decreased from the preinfusion value of 0.49 +/- 0.01 mmol/L in the control group (0.34 +/- 0.03 mmol/L) but remained within normal ranges in the maintenance group (0.46 +/- 0.02 mmol/L with a pump infusing 72 mg/kg per hour and 0.56 +/- 0.05 mmol/L with a pump infusing 24 mg/kg hour). There was an inverse relationship between the maintenance dose and neuronal loss but not between the maintenance dose and mortality rate.

CONCLUSION

Long-term magnesium administration had neuroprotective effects against hypoxia-ischemia in newborn rats.

Magnesium sulfate for tocolysis and risk of spastic cerebral palsy in premature children born to women without preeclampsia

OBJECTIVE

Our aim was to examine magnesium sulfate tocolysis and cerebral palsy in infants born prematurely to women without preeclampsia.

STUDY DESIGN

We conducted a retrospective case-control study of infants with birth weights <1500 g and of infants with birth weights from 1500 to 1999 g who were born at <33 weeks' gestation. The study infants were born in level 2 or level 3 hospitals from 1988 through 1994 to women without preeclampsia, were delivered >3 hours after admission, and had survived to age 2 years.

RESULTS

Among 170 children with cerebral palsy and 288 control subjects, similar proportions of case mothers (58%) and control mothers (62%) had received magnesium sulfate tocolysis. In women with some tocolytic treatment, these proportions were 78% and 76%, respectively. The duration of treatment with magnesium was comparable for case and control women, as were the intervals from beginning and termination of treatment to delivery. Adjustment for gestational age, birth weight, and other variables did not alter this result.

CONCLUSION

Magnesium exposure was not associated with a lower risk of cerebral palsy in infants born prematurely to women without preeclampsia. The difference between this finding and that in our previous study showing an apparent neuroprotective effect of magnesium is not explained by the more restrictive selection criteria used here and may be related to a number of changes in medical practice between the 2 periods.

Maternal infection, fetal inflammatory response, and brain damage in very low birth weight infants. Developmental Epidemiology Network Investigators

Echolucent images (EL) of cerebral white matter, seen on cranial ultrasonographic scans of very low birth weight newborns, predict motor and cognitive limitations. We tested the hypothesis that markers of maternal and feto-placental infection were associated with risks of both early (diagnosed at a median age of 7 d) and late (median age = 21 d) EL in a multi-center cohort of 1078 infants <1500 x g. Maternal infection was indicated by fever, leukocytosis, and receipt of antibiotic; fetoplacental inflammation was indicated by the presence of fetal vasculitis (i.e. of the placental chorionic plate or the umbilical cord). The effect of membrane inflammation was also assessed. All analyses were performed separately in infants born within 1 h of membrane rupture (n = 537), or after a longer interval (n = 541), to determine whether infection markers have different effects in infants who are unlikely to have experienced ascending amniotic sac infection as a consequence of membrane rupture. Placental membrane inflammation by itself was not associated with risk of EL at any time. The risks of both early and late EL were substantially increased in infants with fetal vasculitis, but the association with early EL was found only in infants born > or =1 after membrane rupture and who had membrane inflammation (adjusted OR not calculable), whereas the association of fetal vasculitis with late EL was seen only in infants born <1 h after membrane rupture (OR = 10.8; p = 0.05). Maternal receipt of antibiotic in the 24 h just before delivery was associated with late EL only if delivery occurred <1 h after membrane rupture (OR = 6.9; p = 0.01). Indicators of maternal infection and of a fetal inflammatory response are strongly and independently associated with EL, particularly late EL.

Antenatal corticosteroids and cranial ultrasonographic abnormalities

OBJECTIVE

This study was undertaken to determine whether very-low-birth-weight infants whose mothers received a course of antenatal corticosteroids were at decreased risk for 3 cranial ultrasonographic entities that predict neurodevelopmental dysfunction.

STUDY DESIGN

This retrospective cohort study evaluated 1604 infants weighing 500 to 1500 g who underwent >/=1 of 3 cranial ultrasonographic scans required by design at specified postnatal intervals and whose own and mother's hospital charts were reviewed. Infants were classified according to mother's course of antenatal corticosteroids (none, partial, or complete).

RESULTS

In the total sample the risks of intraventricular hemorrhage and of an echolucent image in the cerebral white matter were only modestly (and not statistically significantly) reduced after a full course of antenatal corticosteroids, whereas antenatal corticosteroids appeared to significantly reduce the risk of ventriculomegaly after even a partial course. Antenatal corticosteroids appeared to halve the risk of ventriculomegaly and echolucent image among the gestationally youngest infants and those with intraventricular hemorrhage, hypothyroxinemia, or vasculitis of the umbilical cord or chorionic plate of the placenta.

CONCLUSION

These observations are consistent with the hypothesis that antenatal corticosteroids protect very-low-birth-weight infants, especially those who are most vulnerable, against the risk of cranial ultrasonographic abnormalities.

Labor and delivery characteristics and risks of cranial ultrasonographic abnormalities among very-low-birth-weight infants. The Developmental Epidemiology Network Investigators

OBJECTIVE

The objective of this study was to evaluate the relationships between 3 labor and delivery characteristics (duration of labor, interval between membrane rupture and delivery, and route of delivery) and 4 neonatal cranial ultrasonographic abnormalities (intraventricular hemorrhage, ventriculomegaly, echodensity of cerebral white matter, and periventricular leukomalacia).

STUDY DESIGN

We prospectively gathered data on 1588 very low birth weight infants including neonatal cranial ultrasonographic studies, maternal interview, and maternal and infant chart reviews. We performed univariate and multivariate analyses.

RESULTS

In univariate analysis vaginal delivery was associated with an increased risk of all 4 cranial ultrasonographic abnormalities. In multivariate analysis, however, vaginal delivery was no longer associated with periventricular leukomalacia. Moreover, the risks of intraventricular hemorrhage, ventriculomegaly, and echodensity attributable to vaginal delivery were no longer elevated when the sample was limited to infants born within 1 hour after membrane rupture and adjustment was made for fetal vasculitis and for other potential confounders.

CONCLUSION

Vaginal delivery was the only obstetric characteristic consistently associated with intracranial hemorrhage and white matter disease in these preterm infants. Because its relationship to brain lesions was markedly reduced when placental inflammation was accounted for, however, vaginal delivery may simply have acted as a marker for antecedent inflammation or infection and not as a direct contributor to brain disorders.

Hypothyroxinemia of prematurity and the risk of cerebral white matter damage

OBJECTIVE

Infants with hypothyroxinemia of prematurity (HOP) are at increased risk for neurodevelopmental dysfunction. Infants born near the end of the middle trimester are also at increased risk for an echolucency (EL) in the cerebral white matter, which reflects white matter damage and is the cranial ultrasound abnormality that best predicts neurodevelopmental dysfunction. We postulated that some of the increased risk of neurodevelopmental problems associated with HOP reflects an increased risk of EL.

STUDY DESIGN

We studied 1414 infants weighing 500 to 1500 g who were born at 4 medical centers between 1991 and 1993. The infants had thyroxine blood levels measured during the first weeks of life, at least 1 of 3 cranial ultrasound scans performed at specified postnatal intervals, and their own and their mother's hospital charts reviewed. Infants were classified by whether or not their first thyroxine level placed them in the lowest quartile among all infants in this sample (ie, <67.8 nmol/L, our definition of HOP, equivalent to <5.3 micrograms/dL).

RESULTS

After adjusting for such potential confounders as low gestational age and measures of illness severity, infants with HOP had twice the risk of EL as their peers with higher thyroxine levels.

CONCLUSION

Our findings are consistent with the hypothesis that a "normal" blood thyroxine level protects infants born near the end of the middle trimester against the risk of cerebral white matter damage.

White matter injury in the preterm infant: an important determination of abnormal neurodevelopment outcome

Periventricular white matter injury, specifically cystic periventricular leukomalacia (PVL) and ipsilateral hemorrhage into white matter associated with periventricular-intraventricular hemorrhage (PV-IVH), contribute significantly to neonatal mortality and long-term neurodevelopmental deficits in the premature infant. The first lesion PVL occurs in approximately 3-4% of infants of birth weight (BW) < 1500 grams. It manifests either as a focal or diffuse lesion within white matter. Although the pathogenesis of PVL is complex and likely multifactorial, principle contributors include vascular factors which markedly increase the risk for ischemia during periods of systemic hypotension and the intrinsic vulnerability of the oligodendrocyte to neurotoxic factors such as free radicals or cytokines. Clinical associations with PVL include a history of chorioamnionitis, prolonged rupture of membranes, asphyxia, sepsis, hypocarbia, etc. The vast majority of infants exhibit long-term neurodevelopmental deficits that affect motor, cognitive and visual function. The second lesion, the ipsilateral hemorrhage into white matter lesion associated with PV-IVH, occurs in approximately 10-15% of infants of BW < 1000 grams. The white matter injury appears to be a venous infarction with hemorrhage occurring as a secondary phenomenon. Prevention of this lesion has to include prevention of the associated PV-IVH. In this regard, the antenatal administration of glucocorticoids has been associated with a significant reduction in the sonographic incidence of severe IVH and the associated white matter involvement. The postnatal administration of indomethacin to high risk infants appears to hold the most promise at the current time in preventing this lesion. The neurodevelopmental outcome with extensive white matter injury is universally poor, affecting long-term motor and cognitive deficits; the long-term outcome is more favorable with lesser involvement. A clearer understanding of pathogenesis of both conditions is essential so as to provide targeted preventative strategies.

Brain injury in the premature infant: overview of clinical aspects, neuropathology, and pathogenesis

Brain injury in the premature infant is an extremely important problem, in part because of the large absolute number of infants affected yearly. The two principal brain lesions that underlie the neurological manifestations subsequently observed in premature infants are periventricular hemorrhagic infarction and periventricular leukomalacia. The emphases of this article are the neurology, neuropathology, and pathogenesis of these two lesions. Recent work suggests that the ultimate goal, prevention of the lesions, is potentially achievable. Periventricular hemorrhagic infarction may be preventable by prevention of germinal matrix/intraventricular hemorrhage, and periventricular leukomalacia, by detection of impaired cerebrovascular autoregulation, prevention of impaired cerebral blood flow, and interruption of the cascade to oligodendroglial cell death by such agents as free-radical scavengers.

Antenatal glucocorticoid, magnesium exposure, and the prevention of brain injury of prematurity

Prevention of perinatal white matter injury with or without severe intraventricular hemorrhage (IVH) is critical to reduce cerebral palsy (CP) in premature infants. Antenatal therapies that may afford neuroprotection include glucocorticoids, which are associated with a significant reduction in severe IVH, and magnesium, which is associated with reduced CP. Potential protective mechanisms of glucocorticoids include a direct effect on brain, improved respiratory function, and more stable blood pressure hemodynamics. Because magnesium is often administered to mothers with pregnancy-induced hypertension, a condition associated with reduction in severe IVH, the independent neuroprotective role of magnesium remains unclear and warrants additional studies.