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

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.

Prophylactic inhibition of NF-κB expression in microglia leads to attenuation of hypoxic ischemic injury of the immature brain

Background

Periventricular leukomalacia (PVL), a devastating brain injury affecting premature infants, is the most common cause of cerebral palsy. PVL is caused by hypoxia ischemia (HI) and is characterized by white matter necrotic lesions, microglial activation, upregulation of NF-κB, and neuronal death. The microglia is the main cell involved in PVL pathogenesis. The goal of this study was to investigate the role of microglial NF-κB activity and its prophylactic inhibition in a neonate mouse model of HI.

Methods

Transgenic mice with specific knockout NF-κB in microglia and colony stimulating factor 1 receptor Cre with floxed IKKβ (CSF-1R Cre + IKKβ^flox/wt ) were used. Postnatal day 5 (P5) mice underwent sham or bilateral temporary carotid artery ligation followed by hypoxia. After HI insult, inflammatory cytokines, volumetric MRI, histopathology, and immunohistochemistry for oligodendroglia and microglial activation markers were analyzed. Long-term neurobehavioral assessment, including grip strength, rotarod, and open field testing, was performed at P60.

Results

We demonstrate that selective inhibition of NF-κB in microglia decreases HI-induced brain injury by decreasing microglial activation, proinflammatory cytokines, and nitrative stress. Rescue of oligodendroglia is evidenced by immunohistochemistry, decreased ventriculomegaly on MRI, and histopathology. This selective inhibition leads to attenuation of paresis, incoordination, and improved grip strength, gait, and locomotion.

Conclusion

We conclude that NF-κb activation in microglia plays a major role in the pathogenesis of hypoxic ischemic injury of the immature brain, and its prophylactic inhibition offers significant neuroprotection. Using a specific inhibitor of microglial NF-κB may offer a new prophylactic or therapeutic alternative in preterm infants affected by HI and possibly other neurological diseases in which microglial activation plays a role.

Protective ventilation of preterm lambs exposed to acute chorioamnionitis does not reduce ventilation-induced lung or brain injury

Background

The onset of mechanical ventilation is a critical time for the initiation of cerebral white matter (WM) injury in preterm neonates, particularly if they are inadvertently exposed to high tidal volumes (V_T) in the delivery room. Protective ventilation strategies at birth reduce ventilation-induced lung and brain inflammation and injury, however its efficacy in a compromised newborn is not known. Chorioamnionitis is a common antecedent of preterm birth, and increases the risk and severity of WM injury. We investigated the effects of high V_T ventilation, after chorioamnionitis, on preterm lung and WM inflammation and injury, and whether a protective ventilation strategy could mitigate the response.

Methods

Pregnant ewes (n = 18) received intra-amniotic lipopolysaccharide (LPS) 2 days before delivery, instrumentation and ventilation at 127±1 days gestation. Lambs were either immediately euthanased and used as unventilated controls (LPS_UVC; n = 6), or were ventilated using an injurious high V_T strategy (LPS_INJ; n = 5) or a protective ventilation strategy (LPS_PROT; n = 7) for a total of 90 min. Mean arterial pressure, heart rate and cerebral haemodynamics and oxygenation were measured continuously. Lungs and brains underwent molecular and histological assessment of inflammation and injury.

Results

LPS_INJ lambs had poorer oxygenation than LPS_PROT lambs. Ventilation requirements and cardiopulmonary and systemic haemodynamics were not different between ventilation strategies. Compared to unventilated lambs, LPS_INJ and LPS_PROT lambs had increases in pro-inflammatory cytokine expression within the lungs and brain, and increased astrogliosis (p<0.02) and cell death (p<0.05) in the WM, which were equivalent in magnitude between groups.

Conclusions

Ventilation after acute chorioamnionitis, irrespective of strategy used, increases haemodynamic instability and lung and cerebral inflammation and injury. Mechanical ventilation is a potential contributor to WM injury in infants exposed to chorioamnionitis.

Chorioamnionitis in the pathogenesis of brain injury in preterm infants

Chorioamnionitis (or placental infection) is suspected to be a risk factor for brain injury in premature infants. The suggested association between chorioamnionitis and cystic periventricular leukomalacia and cerebral palsy is uncertain because of the variability of study designs and definitions of chorioamnionitis. Improvements in neonatal intensive care may have attenuated the impact of chorioamnionitis on brain health outcomes. Large multicenter studies using rigorous definitions of chorioamnionitis on placental pathologies and quantitative magnetic resonance techniques may offer the optimal way to clarify the complex role of chorioamnionitis in modifying brain health and long-term outcomes.

It is not the ride: inter-hospital transport is not an independent risk factor for intraventricular hemorrhage among very low birth weight infants

OBJECTIVE

The purpose of this study was to evaluate the relationship between intraventricular hemorrhage (IVH), inter-hospital transport and known potential risk factors for IVH.

STUDY DESIGN

Very low birth weight (VLBW <1500 g) infants admitted to a large regional neonatal intensive care unit within 48 h of life from 2005 to 2010 were identified. Logistic regression and proportional odds logistic regression models were used to compare inborn versus outborn patients with respect to IVH (any vs none) and IVH grade, respectively. Logistic regression was used to quantify the association between outborn status and mortality.

RESULT

A total of 758 infants were included in the study (inborn=568, outborn=190). Outborn infants were found to have greater IVH severity than inborn (odds ratio (OR): 1.52; P=0.012). After accounting for 20 clinical and demographic variables in a multivariable model, the association between outborn status and IVH lacked statistical significance (OR: 1.14; P=0.56). Significant predictors of IVH grade included vaginal delivery (OR: 2.16; P<0.001), patent ductus arteriosus (OR: 1.65; P=0.005), 5-min Apgar (OR: 0.85; P=0.005) and gestational age (OR: 0.98; P=0.012). Sixty-nine (9.1%) of the infants died. After adjusting for potential confounders, the relationship between mortality and outborn status was not significant (OR:1.26; P=0.516). Significant predictors of mortality included gestational age (OR: 1.03; P=0.04) and 5-min Apgar (OR:1.22; P=0.02).

CONCLUSION

Although VLBW infants transported during the first 2 days of life have higher rates of IVH than infants born at a tertiary care facility, this relationship may be explained by associations with underlying clinical variables rather than transport itself.

Neurodevelopmental outcomes in very low-birth-weight infants in Korea: 1998-2007 vs 1989-1997

The authors reviewed the medical records of very low-birth-weight infants admitted from 1998 to 2007 and compared neurodevelopmental outcomes with their previously reported data from 1989 to 1997. The recent group included 824 infants, and the previous group included 471 infants. Neurodevelopmental outcomes were classified into cerebral palsy and non-cerebral palsy neurodevelopmental impairment. In the recent group, the survival rate was significantly higher (79.4% vs 66.2%), the rate of cerebral palsy was lower (7.9% vs 10.5%), and the rate of non-cerebral palsy neurodevelopmental impairment was higher (6.0% vs 4.5%) but not significant. The survival rate increased significantly over time, but there was no significant change in neurodevelopmental outcomes over time. Multivariate analysis indicated that abnormal neurosonographic findings, using assisted ventilation, vaginal delivery, and abnormal brainstem auditory evoked potential, were associated with increased risk for cerebral palsy.

Sex differences in intraventricular hemorrhage rates among very low birth weight newborns

BACKGROUND

The influence of male or female sex on newborn outcomes has been recognized for >30 years. Several studies have observed higher mortality and morbidity in males than in females. It is not clear how this sex difference is sustained in postnatal complications such as intraventricular hemorrhage (IVH), especially in very low birth weight (VLBW) newborns.

OBJECTIVE

This study examined possible sex-related differences in IVH rates among VLBW neonates.

METHODS

In a retrospective observational study conducted in Hospital Privado, Córdoba, Argentina, data from 332 consecutive VLBW newborns in a 12-year period were reviewed. Maternal factors, labor and delivery characteristics, and neonatal parameters, including the results of cranial ultrasound examination to detect IVH, were compared for males and females. Bivariate and multivariate logistic regression analyses were performed.

RESULTS

A total of 322 VLBW newborns were included, 168 males and 154 females. Compared with female neonates, male neonates had a higher risk of overall IVH (26.8% vs 9.7%; odds ratio [OR] = 3.4 [95% CI, 1.8-6.4]; P < 0.001) and for grades III or IV on the Papile scale (16.1% vs 1.9%; OR = 9.6 [95% CI, 2.9-32.5]; P < 0.001). In the multivariate logistic regression model, male sex sustained the association with a greater risk of IVH (OR = 6.8 [95% CI, 3.8-12.0]).

CONCLUSIONS

IVH was significantly associated with male sex in these VLBW newborns. Because other factors affect these differences, further research is required.

The relationship between systemic hemodynamic perturbations and periventricular-intraventricular hemorrhage--a historical perspective

Periventricular-intraventricular hemorrhage (PV-IVH) remains the major cause of injury to the developing brain. Predisposing factors include a germinal matrix with an immature vasculature, a pressure passive cerebral circulation, and hemodynamic perturbations in sick premature infants. Intact cerebral autoregulation has been documented in stable premature infants; however, it functions within a limited blood pressure range and is likely to be absent in the sick hypotensive infant, which increases the risk for PV-IVH with perturbations in blood pressure. The risk for PV-IVH is markedly increased in the absence of antenatal glucocorticoid exposure in the intubated low birthweight infant <1000 g with respiratory distress syndrome; +/- other complications. Although surfactant administration reduces the severity of respiratory distress syndrome, it has not led to a reduction in PV-IVH. Early postnatal administration of indomethacin has been associated with a reduction in PV-IVH, although this has not translated into long-term neurocognitive benefits.

Intracranial hemorrhage in the preterm infant: understanding it, preventing it

New discoveries in neonatal imaging, cerebral monitoring, and hemodynamics, and greater understanding of inflammatory and genetic mechanisms involved in intracranial hemorrhage (ICH) in the preterm infant are creating opportunities for innovative early detection and prevention approaches. This article covers the spectrum of ICH in the preterm infant, including germinal matrix intraventricular hemorrhage, its complications, and associated phenomena, such as the emerging role of cerebellar hemorrhage. The overall aim of this article is to review the current knowledge of the mechanisms, diagnosis, outcome, and management of preterm ICH; to revisit the origins from which they develop; and to discuss future expectations.

Does cesarean section prevent mortality and cerebral ultrasound abnormalities in preterm newborns?

OBJECTIVE

Despite the increased use of the cesarean section (CS), the rates of cerebral palsy, a frequent consequence of brain damage, have remained stable over the last decades. Whether an actual decrease in cerebral palsy has been masked by increased survival of infants delivered by CS or not, remains undefined. To investigate the role of CS, we compared risks of mortality and brain damage, as defined by ultrasound (US) abnormalities, in preterm newborns by mode of delivery.

METHODS

Information on fetal, maternal, and neonatal risk factors was collected from the paired clinical records of preterm newborns and mothers. Crude and adjusted odds ratios (OR) of mortality and ultrasound abnormalities, according to mode of delivery (i.e., vaginal, elective CS, and emergency CS) were calculated. All the analyses were controlled for possible confounding by indication.

RESULTS

In newborns of gestational age <32 weeks, no effect of CS on cerebral US abnormalities was found (OR 0.71 and 0.73 for emergency CS and elective CS, respectively). None of the maternal and neonatal factors were associated with both cerebral US abnormalities and mode of delivery. Among newborns of gestational age >or=32 weeks, after controlling for known and potential confounders in a multivariate model, the adjusted ORs remained close to one for both elective CS and emergency CS.

CONCLUSIONS

CS does not reduce overall mortality in preterm newborns. No protective effect of CS on US abnormalities was found after stratifying by gestational age and controlling for possible confounding. These results do not encourage the widespread use of CS in preterm labor.

Cystic periventricular leukomalacia in preterm infants: an analysis of obstetric risk factors

OBJECTIVE

To identify obstetric risk factors and to elucidate the effect of prolonged rupture of the membranes on the development of cystic periventricular leukomalacia (PVL) in preterm infants.

METHODS

A retrospective case-control study of 95 preterm infants with the diagnosis of PVL and 245 healthy controls matched for gestational age. A total of 52 antenatal, intrapartum and neonatal characteristics were studied by univariate methods and logistic regression.

RESULTS

Preterm premature rupture of membranes (PPROM) (odds ratio 2.1 [95% CI 1.3-3.4], P=.003), gestational age at PPROM (P=.025), prolonged rupture of membranes (P<.0001), administration of tocolytic agents (1.8 [1.1-3.0], P=.019) and antibiotics (1.9 [1.2-3.1], P=.008) were associated with PVL. The use of tocolytic agents >24 h (P=.008), prolonged latency between the increase in maternal leukocyte count and birth (P=.034), spontaneous onset of labor (1.8 [1.0-2.9], P=.026), vaginal delivery (1.7 [1.1-2.8], P=.029) and male gender (1.5 [1.0-2.0], P=.04) were found more frequently in PVL cases. Preeclampsia (0.4 [0.1-0.9], P=.034), hypertension at booking (P=.009), sonographic IUGR (P=.020), abnormal blood flow of the umbilical artery (P=.032) and cesarean section without labor (0.5 [0.3-0.8], P=.006) were found less frequently. In logistic regression analysis, prolonged rupture of the membranes (P=.748), preeclampsia (P=.973), the use of antibiotics (P=.617) and beta-sympathomimetic tocolytic agents (P=.563) lost statistical significance, whereas birth weight (P=.036) became significant.

CONCLUSION

PPROM and prolonged rupture of the membranes may provoke adverse effects on the neurodevelopmental outcome of the preterm fetus. These findings may have implications on the obstetric management of PPROM beyond 30 weeks of gestation. Cesarean section without labor was less likely associated with the diagnosis of PVL.

Brain imaging findings in very preterm infants throughout the neonatal period: part II. Relation with perinatal clinical data

This study describes the relation between frequent and clinically relevant brain imaging findings in very preterm infants (GA<32 weeks), assessed with sequential cranial ultrasonography throughout the neonatal period and MRI around term age, and several potential perinatal risk factors. For ultrasound findings during admission the following independent risk factors were identified: male gender for periventricular echodensities and intraventricular haemorrhage, postnatal corticosteroid treatment for cystic white matter lesions, and lower gestational age for post-haemorrhagic ventricular dilatation. For MRI findings around term age, including punctate white matter lesions, ventricular dilatation, decreased cortical complexity, and diffuse and excessive high signal intensity, no independent risk factors were found. In very preterm infants, the risk factors for frequently found changes on cranial ultrasound have largely remained unchanged over the last decades, while no risk factors could be identified for subtle and diffuse white matter injury as seen on MRI around term age.

Risk factors for adverse outcome in preterm infants with periventricular hemorrhagic infarction

OBJECTIVE

Our objective was to identify risk factors that were associated with mortality and adverse neurologic outcome at 18 months of age in preterm infants with periventricular hemorrhagic infarction.

METHODS

This was a retrospective cohort study of all preterm infants who were <37 weeks' gestation, had periventricular hemorrhagic infarction, and were admitted between 1995 and 2006. Ultrasound scans were reviewed for grading of germinal matrix hemorrhage, localization and extension of the infarction, and other abnormalities. Several clinical factors were scored. Outcome measures were mortality, cerebral palsy, and Gross Motor Function Classification System level. Odds ratios were calculated by univariate and multivariate logistic regression analyses.

RESULTS

Of 54 infants, 16 (30%) died. Twenty-five (66%) of 38 survivors developed cerebral palsy: 21 mild (Gross Motor Function Classification System levels 1 and 2) and 4 moderate to severe (levels 3 and 4). Several perinatal and neonatal risk factors were associated with mortality. After multivariate logistic regression, only use of inotropic drugs and maternal intrauterine infection were predictors of mortality. In survivors, only the most extended form of periventricular hemorrhagic infarction was associated with the development of cerebral palsy but not with severity of cerebral palsy. Cystic periventricular leukomalacia and concurrent grade 3 germinal matrix hemorrhage were associated with more severe cerebral palsy.

CONCLUSIONS

In preterm infants with periventricular hemorrhagic infarction, mortality occurred despite optimal treatment and was associated with circulatory failure and maternal intrauterine infection. In survivors, motor development was abnormal in 66%, but functional abilities were good in the majority. Extension and localization of the periventricular hemorrhagic infarction were not related to functional outcome.

Bruising at birth: antenatal associations and neonatal outcome of extremely low birth weight infants

BACKGROUND

Early studies have identified severe cranial bruising as a risk factor for intraventricular hemorrhage (IVH) in premature infants but the nature of this association has not been evaluated.

OBJECTIVE

To identify antenatal predictors and associations with neonatal outcome of bruised extremely low birth weight infants.

METHODS

A cohort study comparing 34 bruised and 116 non-bruised infants (birth weight <or=1,000 g), delivered in two 'Hadassah' university hospitals in Jerusalem between 2000 and 2004. Bruised patients were divided according to the severity of bruising. A univariate model was first applied to examine the associations of the individual independent variables with the outcome variable, followed with a logistic stepwise regression model, performed for each of the outcome variables.

RESULTS

In a stepwise logistic regression on 'Any bruising' and 'Severe bruising', only increasing gestational age and exposure to antenatal steroids prior to delivery maintained a protective association with bruising (OR = 0.74; 95% CI: 0.58-0.94; p = 0.015, OR = 0.38; 95% CI: 0.16-0.90; p = 0.028, respectively, for 'Any bruising', and OR = 0.77; 95% CI: 0.59-1.01; p = 0.055, OR = 0.29; 95% CI: 0.12-0.73; p = 0.008, respectively, for 'Severe bruising'). In a stepwise logistic regression analysis, with 'Any bruising' and 'Severe bruising' as forced-in variables and controlling for gestational age, small for gestational age, Apgar scores, respiratory distress syndrome and pneumothorax, 'Severe bruising', but not 'Any bruising', was found to be associated significantly with severe IVH (OR = 5.60; 95% CI: 1.86-16.82; p = 0.002), whereas both 'Any bruising' and 'Severe bruising' were significantly associated with mortality (OR = 6.31; 95% CI: 2.37-16.83; p = 0.000, OR = 3.33; 95% CI: 1.16-9.52; p = 0.025 respectively).

CONCLUSION

Antenatal exposure to steroids and increasing gestational age are associated with a lower incidence of bruising at birth in extremely low birth weight infants. Severe bruising at birth is associated with increased incidence of severe intraventricular hemorrhage and mortality.

[Ultrasonic findings of intracranial hemorrhage in preterm neonates]

Intracranial hemorrhage ICH is one of the most common neurological events in pre-term newborn ICH is associated with low birth weight (< 1500 g) and gestational age (GA) at delivery (< 32 weeks). The most common site affected is the germinal matrix. Papile et al. classifies it at four grades. We analyzed, prospectively, 50 newborns (27 boys) with ultrasound diagnostic of ICH; all of them were pre-term (GA < 37 weeks). They were classified according to sex, gestational age, birth weight and degree of ICH. The children were divided into two groups: A--GA < or = 33 weeks and B--34-37 weeks. In group A there were 34 children (25 boys) with mean GA of 31 weeks and birth weights average of 1308 g. In group B there were 16 children (2 boys), mean GA 34 weeks and birth weight average of 1951 g. The grades of ICH were: Group A--I-14, II-14, III-4 and IV-2; Group B--I-12, II-3 and III-1. The complications were more common in group A with 12 than group B with 4 children. The lesions happen in greatest number and most severity in children with low birth weight and younger (low gestational age). Ultrasound has shown to be effective for diagnostic and follow up of those children.

Duration of labor and risk of cerebral white-matter damage in very preterm infants who are delivered with intrauterine infection

OBJECTIVE

The purpose of this study was to assess whether the duration of labor has any effect on the occurrence of cerebral white-matter damage in very preterm infants who are delivered in the presence of intrauterine infection.

STUDY DESIGN

From a cohort of infants who were born spontaneously at <32 weeks of gestation for whom placental information was available and who survived 7 days from birth, 126 infants had clinical, laboratory, or histologic evidence of intrauterine infection. Among them, variables were compared between those infants with white-matter damage (defined as intraventricular hemorrhage grade 3 plus, periventricular leukomalacia, or ventriculomegaly not associated with hydrocephaly [n = 13]) and those infants without it (n = 113). Comparisons were made with t test, chi-squared test, and survival analysis; a probability value of <.05 was considered significant.

RESULTS

There were no differences between the 2 groups in gestational age at delivery and rates of labor or cesarean delivery. Duration of active labor (66 +/- 45 minutes vs 88 +/- 75 minutes; P =.49) and of clinical chorioamnionitis (310 +/- 186 minutes vs 529 +/- 544 minutes; P =.44) were similar in cases with and without neonatal white-matter damage.

CONCLUSION

In 126 infants who were born at <32 weeks of gestation with intrauterine infection, we found no correlation between the duration of labor or clinical chorioamnionitis and neonatal white-matter damage.

Intraventricular Hemorrhage and Periventricular Leukomalacia in Preterm Infants

OBJECTIVE

To evaluate whether intraventricular hemorrhage and periventricular leukomalacia are characterized by different risk factors.

METHODS

In a cohort of 653 consecutive singleton neonates born after preterm membrane rupture, spontaneous preterm labor, or indicated preterm delivery at 24 to 33 weeks of gestation from January 1, 1993, to December 31, 2002, we evaluated the obstetric and histopathologic placental variables in reference to the development of intraventricular hemorrhage (n = 44), periventricular leukomalacia (n = 19), or no ultrasonographic cerebral lesion (n = 589). Excluded were stillbirths and congenital anomalies. Statistical analysis included Fisher exact test, Student t test, and stepwise logistic regression analysis with a 2-tailed P <.05 considered significant.

RESULTS

Multivariate analysis showed that occurrence of neonatal intraventricular hemorrhage and periventricular leukomalacia were associated only with spontaneous prematurity (odds ratio = 1.9; 95% confidence interval 1.1-3.4) and gestational age at delivery in weeks (odds ratio = 0.8; 95% confidence interval 0.7-0.9). Neonates with intraventricular hemorrhage did not differ from those with periventricular leukomalacia in any obstetric or neonatal variable, but there was a higher risk of neurodevelopmental delay associated with periventricular leukomalacia.

CONCLUSION

Among premature infants born at less than 34.0 weeks of gestation, intraventricular hemorrhage and periventricular leukomalacia share common clinical characteristics, with spontaneous preterm delivery and gestational age at delivery as the only independent antenatal predictors.

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.

Risk factors for intraventricular hemorrhage in very low birth weight premature infants: a retrospective case-control study

OBJECTIVE

High-grade intraventricular hemorrhage (IVH) is an important cause of severe cognitive and motor neurologic impairment in very low birth weight infants and is associated with a high mortality rate. The risk of IVH is inversely related to gestational age and birth weight. Previous studies have proposed a number of risk factors for IVH; however, lack of adequate matching for gestational age and birth weight may have confounded the results. The purpose of this study was to identify variables that affect the risk of high-grade IVH, using a retrospective and case-control clinical study.

METHODS

From a cohort of 641 consecutive preterm infants with a birth weight of <1500 g, 36 infants with IVH grade 3 and/or 4 were identified. A control group of 69 infants, closely matched for gestational age and birth weight, was selected. Maternal factors, labor and delivery characteristics, and neonatal parameters were collected in both groups. Results of cranial ultrasound examinations, whether routine or performed in presence of clinical suspicion, were also collected. Univariate analysis and multivariate logistic regression analysis were performed.

RESULTS

High fraction of inspired oxygen in the first 24 hours, pneumothorax, fertility treatment (mostly IVF), and early sepsis were associated with an increased risk of IVH. A higher number of suctioning procedures, a higher first hematocrit, and a relatively low arterial pressure of carbon dioxide during the first 24 hours of life were associated with a lower occurrence. In the multivariate logistic regression model, early sepsis (odds ratio [OR]: 8.19; 95% confidence interval [CI]: 1.55-43.1) and fertility treatment (OR: 4.34; 95% CI: 1.42-13.3) were associated with a greater risk of high-grade IVH, whereas for every dose of antenatal steroid treatment there was a lower risk of high-grade IVH (OR: 0.52; 95% CI: 0.30-0.90) and each decrease in a mmHg unit of arterial pressure of carbon dioxide during the first 24 hours was associated with a lower risk of IVH (OR: 0.91; 95% CI: 0.83-0.98). This multivariate model had a sensitivity of 77%, a specificity of 75%, and a positive predictive value of 76%. The area under the curve derived from the receiver operator characteristic plots is 0.82.

CONCLUSIONS

Our results confirm that the development of IVH is associated with early sepsis and failure to give antenatal steroid treatment. We propose that fertility treatment (and especially IVF) may be a new risk factor, and more research is needed to assess its role.

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.

The toll-like receptor TLR4 is necessary for lipopolysaccharide-induced oligodendrocyte injury in the CNS

The immediate or innate immune response is the first line of defense against diverse microbial pathogens and requires the expression of recently discovered toll-like receptors (TLRs). TLR4 serves as a specific receptor for lipopolysaccharide (LPS) and is localized on the surface of a subset of mammalian cells. Although innate immunity is a necessary host defense against microbial pathogens, the consequences of its activation in the CNS can be deleterious, as we show here in a developing neural model. We examined the major non-neuronal cell types in the CNS for expression of TLR4 and found that microglia expressed high levels, whereas astrocytes and oligodendrocytes expressed none. Consistent with TLR4 expression solely in microglia, we show that microglia are the only CNS glial cells that bind fluorescently tagged lipopolysaccharide. Lipopolysaccharide led to extensive oligodendrocyte death in culture only under conditions in which microglia were present. To determine whether TLR4 is necessary for lipopolysaccharide-induced oligodendrocyte death in mixed glial cultures, we studied cultures generated from mice bearing a loss-of-function mutation in the tlr4 gene. Lipopolysaccharide failed to induce oligodendrocyte death in such cultures, in contrast to the death induced in cultures from wild-type mice. Finally, stereotactic intracerebral injection of lipopolysaccharide into the developing pericallosal white matter of immature rodents resulted in loss of oligodendrocytes and hypomyelination and periventricular cysts. Our data provide a general mechanistic link between (1) lipopolysaccharide and similar microbial molecular motifs and (2) injury to oligodendrocytes and myelin as occurs in periventricular leukomalacia and multiple sclerosis.

Neurobiology of periventricular leukomalacia in the premature infant

Brain injury in the premature infant is a problem of enormous importance. Periventricular leukomalacia (PVL) is the major neuropathologic form of this brain injury and underlies most of the neurologic morbidity encountered in survivors of premature birth. Prevention of PVL now seems ultimately achievable because of recent neurobiologic insights into pathogenesis. The pathogenesis of this lesion relates to three major interacting factors. The first two of these, an incomplete state of development of the vascular supply to the cerebral white matter, and a maturation-dependent impairment in regulation of cerebral blood flow underlie a propensity for ischemic injury to cerebral white matter. The third major pathogenetic factor is the maturation-dependent vulnerability of the oligodendroglial (OL) precursor cell that represents the major cellular target in PVL. Recent neurobiologic studies show that these cells are exquisitely vulnerable to attack by free radicals, known to be generated in abundance with ischemia-reperfusion. This vulnerability of OLs is maturation-dependent, with the OL precursor cell highly vulnerable and the mature OL resistant, and appears to relate to a developmental window characterized by a combination of deficient antioxidant defenses and active acquisition of iron during OL differentiation. The result is generation of deadly reactive oxygen species and apoptotic OL death. Important contributory factors in pathogenesis interact with this central theme of vulnerability to free radical attack. Thus, the increased likelihood of PVL in the presence of intraventricular hemorrhage could relate to increases in local iron concentrations derived from the hemorrhage. The important contributory role of maternal/fetal infection or inflammation and cytokines in the pathogenesis of PVL could be related to effects on the cerebral vasculature and cerebral hemodynamics, to generation of reactive oxygen species, or to direct toxic effects on vulnerable OL precursors. A key role for elevations in extracellular glutamate, caused by ischemia-reperfusion, is suggested by demonstrations that glutamate causes toxicity to OL precursors by both nonreceptor- and receptor-mediated mechanisms. The former involves an exacerbation of the impairment in antioxidant defenses, and the latter, an alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid/kainate receptor-mediated cell death. Most importantly, these new insights into the pathogenesis of PVL suggest potential preventive interventions. These include avoidance of cerebral ischemia by detection of infants with impaired cerebrovascular autoregulation, e.g. through the use of in vivo near-infrared spectroscopy, the use of free radical scavengers to prevent toxicity by reactive oxygen species, the administration of alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid/kainate receptor antagonists to prevent glutamate-mediated injury, or the use of maternal antibiotics or anticytokine agents to prevent toxicity from maternal/fetal infection or inflammation and cytokines.

New developments in the management of preterm labor

Current management of preterm labor has not changed the incidence of preterm delivery; therefore, significant research effort has been concentrated on the search for new methods of management. New tocolytics like inhibitors of cyclooxygenase 2 and nitric oxide donors have been tested in animal models and in preliminary clinical trials with promising results. Inhibition of cervical ripening may be one alternative to tocolysis. This new approach has a potential to be a valuable method of management of preterm labor if human studies confirm the promising results reported in animals. Growing evidence suggests that premature delivery may be associated with infection or fetal growth abnormalities, with dire consequences to the fetus. If these associations are to be included in risk and benefit assessment, then inhibition of preterm labor may prove to be detrimental to the fetus.

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.