Antecedents and outcome of very early neonatal seizures in infants born at or after term

Seizure Burden and Neurologic Outcomes After Neonatal Encephalopathy

BACKGROUND AND OBJECTIVES

Seizures are common during neonatal encephalopathy (NE), but the contribution of seizure burden (SB) to outcomes remains controversial. This study aims to examine the relationship between electrographic SB and neurologic outcomes after NE.

METHODS

This prospective cohort study recruited newborns ≥36 weeks postmenstrual age around 6 hours of life between August 2014 and November 2019 from a neonatal intensive care unit (NICU). Participants underwent continuous electroencephalography for at least 48 hours, brain MRI within 3-5 days of life, and structured follow-up at 18 months. Electrographic seizures were identified by board-certified neurophysiologists and quantified as total SB and maximum hourly SB. A medication exposure score was calculated based on all antiseizure medications given during NICU admission. Brain MRI injury severity was classified based on basal ganglia and watershed scores. Developmental outcomes were measured using the Bayley Scales of Infant Development, Third Edition. Multivariable regression analyses were performed, adjusting for significant potential confounders.

RESULTS

Of 108 enrolled infants, 98 had continuous EEG (cEEG) and MRI data collected, of which 5 were lost to follow-up, and 6 died before age 18 months. All infants with moderate-severe encephalopathy completed therapeutic hypothermia. cEEG-confirmed neonatal seizures occurred in 21 (24%) newborns, with a total SB mean of 12.5 ± 36.4 minutes and a maximum hourly SB mean of 4 ± 10 min/h. After adjusting for MRI brain injury severity and medication exposure, total SB was significantly associated with lower cognitive (-0.21, 95% CI -0.33 to -0.08, p = 0.002) and language (-0.25, 95% CI -0.39 to -0.11, p = 0.001) scores at 18 months. Total SB of 60 minutes was associated with 15-point decline in language scores and 70 minutes for cognitive scores. However, SB was not significantly associated with epilepsy, neuromotor score, or cerebral palsy (p > 0.1).

DISCUSSION

Higher SB during NE was independently associated with worse cognitive and language scores at 18 months, even after adjusting for exposure to antiseizure medications and severity of brain injury. These observations support the hypothesis that neonatal seizures occurring during NE independently contribute to long-term outcomes.

Antenatal factors for neonatal seizures among late preterm births

OBJECTIVE

The objective of this study was to evaluate for antenatal risk factors for neonatal seizures among late preterm births.

STUDY DESIGN

This was a case control study which included late preterm births without anomaly from the United States Natality database. Cases were infants with neonatal seizures, while the controls consisted of infants without neonatal seizures. Maternal and pregnancy characteristics were compared. Multivariable logistic regression was performed to investigate risk factors for neonatal seizures.

RESULTS

Of the 943,580 late preterm births, 512 (0.05%) developed neonatal seizures. Significant risk factors associated with neonatal seizures among late preterm births included number of prenatal visits (adjusted odds ratio [aOR] 0.94, 95% CI [0.92-0.96]), smoking history (aOR 1.78, 95% CI [1.41-2.25]), chorioamnionitis (aOR 4.37, 95% CI [2.65-7.21]), non-Hispanic White race (aOR 1.41, 95% CI [1.13-1.76]), and cesarean birth (aOR 2.31, 95% CI [1.91-2.80]).

CONCLUSION

Number of prenatal visits, history of smoking, chorioamnionitis, non-Hispanic white race, and cesarean birth are risk factors for neonatal seizures at late preterm gestation.

Risk factors for seizures in the vigorous term neonate: A population-based register study of singleton births in Sweden

Background

Neonatal seizures have been associated with increased mortality and impaired neurodevelopment and, knowledge about risk factors may be useful for prevention. Clear associations have been established between labor-related risk factors and seizures in asphyxiated neonates. However, there is limited information about why some vigorous term-born infants experience seizures.

Objectives

Our aim was to assess antepartum and intrapartum risk factors for seizures in vigorous term-born neonates.

Methods

This was a national cohort study of singleton infants born at term in Sweden from 2009–2015. Vigorous was defined as an Apgar score of at least 7 at 5 and 10 minutes. Data on the mothers and infants were obtained from the Swedish Medical Birth Register and the Swedish Neonatal Quality Register. A diagnosis of neonatal seizures was the main outcome measure and the exposures were pregnancy and labor variables. Logistic regression analysis was used and the results are expressed as adjusted odds ratios (aOR) with 95% confidence intervals (CI).

Results

The incidence of neonatal seizures was 0.81/1,000 for 656 088 births. Seizures were strongly associated with obstetric emergencies (aOR 4.0, 95% CI 2.2–7.4), intrapartum fever and/or chorioamnionitis (aOR 3.4, 95% CI 2.1–5.3), and intrapartum fetal distress (aOR 3.0, 95% CI 2.4–3.7). Other associated intrapartum factors were: labor dystocia, occiput posterior position, operative vaginal delivery, and Cesarean delivery. Some maternal factors more than doubled the risk: a body mass of more than 40 (aOR 2.6, 95% CI 1.4–4.8), hypertensive disorders (aOR 2.3, 95% CI 1.7–3.1) and diabetes mellitus (aOR 2.6, 95% CI 1.7–4.1).

Conclusion

A number of intrapartum factors were associated with an increased risk of seizures in vigorous term-born neonates. Obstetric emergencies, intrapartum fever and/or chorioamnionitis and fetal distress were the strongest associated risks. The presence of such factors, despite a reassuring Apgar score could prompt close surveillance.

Risk factors for neonatal seizures: A case-control study in the province of Parma, Italy

PURPOSE

The present study evaluated the risk factors for electroencephalographic (EEG)-confirmed seizures during the whole neonatal period in preterm and term neonates born in the province of Parma between January 2009 and December 2014.

METHODS

We selected as cases the infants that presented EEG-confirmed neonatal seizures (NS). Two population controls for each case were matched by gestational age (GA), sex, hospital, and period of birth. Information on the mother, the pregnancy, the labor and delivery, and the neonates were taken from the Emilia-Romagna Certificate of Delivery Assistance database and from hospital charts and ICD-9-CM codes.

RESULTS AND INTERPRETATION

In the 6-year period of this study, 22 patients were recorded with NS. The association between at least one pregnancy complication and at least one neonatal complication, a low Apgar score, the need for resuscitation at birth, intraventricular hemorrhages (IVH) grades II-IV for preterm, and acute perinatal asphyxia/hypoxic-ischemic encephalopathy (HIE) for term infants were all statistically significant among cases. Neonates presenting these risk factors are more prone to develop NS and have to be strictly monitored.

Lack of response to treatment with levetiracetam in extreme preterm infants with seizures

OBJECTIVE

The aim of this study was to evaluate the effectiveness of monotherapy with levetiracetam (LEV) in achieving seizure cessation in a retrospective cohort of extreme preterm infants with seizures.

STUDY DESIGN

Charts of infants with a diagnosis of neonatal seizures admitted to the NICU between 2013 and 2017 were reviewed. Seizures were diagnosed using continuous video electroencephalography. All infants were initially started on LEV and reached a dose of 80 mg/kg/day. Other ASMs were added to LEV if seizures continued after 2 days. Data on additional clinical variables were collected for each infant.

RESULT

Sixty-one infants born <28 weeks of gestation met inclusion criteria. Seventy-four percent of patients did not respond to LEV monotherapy and required additional medications.

CONCLUSIONS

LEV monotherapy stopped seizures in only a small portion of cases.

Seizures in newborn infants without hypoxic ischemic encephalopathy - antenatal and labor-related risk factors: a case-control study

Objective: To identify antepartum and intrapartum risk factors for neonatal seizures in the absence of hypoxic ischemic encephalopathy (HIE).Methods: Population-based case-control study. Of 98 484 births, 40 newborns at 34 gestational weeks or later had seizures within the first 7 days of life. Cases (n = 40) and controls (n = 160) were retrieved from the University hospitals of Örebro for 1994-2013 and Uppsala for 2003-2013. Demographics and characteristics of pregnancy, labor, delivery, and neonatal data were analyzed. Crude odds ratio (OR) and adjusted odds ratios (AOR) with 95% confidence intervals (CIs) for antenatal and intrapartum factors were calculated using logistic regression analysis. Main outcome measure was neonatal seizures within the first 7 days of life.Results: The incidence of neonatal seizures without HIE was 0.41/1000 live births. Antenatal risk factors for neonatal seizures were as follows: short maternal stature (AOR: 5.4; 1.8-16.5); previous caesarean section (AOR: 4.8; 1.5-15.0); and assisted fertilization (AOR: 6.8; 1.3-35.2). Intrapartum risk factors were as follows: induction of labor (AOR: 5.7; 1.8-17.7); preterm birth (AOR: 13.5; 3.7-48.9); and head circumference >37 cm (AOR: 6.9; 1.4-34.8).Conclusions: Preterm birth was the strongest risk factor for neonatal seizures in the absence of HIE. The results also indicate that feto-pelvic disproportion is associated with the occurrence of seizures.Rationale: Antepartum and intrapartum risk factors for newborn seizures in the absence of HIE were investigated in a case-control study. Out of 98 484 births at 34 gestational weeks or more, 40 newborns had seizures without HIE. All had a normal Apgar score although they later presented with seizures. Preterm birth was the strongest risk factor (OR: 13.5; 95% CI: 3.7-48.9). Our results also indicate that feto-pelvic disproportion is of importance. Furthermore, a history of prior caesarean was associated with seizures. This is the first study to assess obstetric risk factors for newborn seizures separate from those with seizures and concomitant HIE. The distinction is of importance due to different etiologies, treatments, and preventive strategies.

Regulation of seizure-induced MeCP2 Ser421 phosphorylation in the developing brain

Neonatal seizures disrupt normal synaptic maturation and often lead to later-life epilepsy and cognitive deficits. During early life, the brain exhibits heightened synaptic plasticity, in part due to a developmental overabundance of Ca_V1.2 L-type voltage gated calcium (Ca²⁺) channels (LT-VGCCs) and Ca²⁺-permeable AMPARs (CP-AMPARs) lacking GluA2 subunits. We hypothesized that early-life seizures overactivate these channels, in turn dysregulating Ca²⁺-dependent signaling pathways including that of methyl CPG binding protein 2 (MeCP2), a transcription factor implicated in the autism spectrum disorder (ASD) Rett Syndrome. Here, we show that in vivo hypoxia-induced seizures (HS) in postnatal day (P)10 rats acutely induced phosphorylation of the neuronal-specific target of activity-dependent MeCP2 phosphorylation, S421, as well as its upstream activator CaMKII T286. We next identified mechanisms by which activity-dependent Ca²⁺ influx induced MeCP2 phosphorylation using in vitro cortical and hippocampal neuronal cultures at embryonic day (E)18 + 10 days in vitro (DIV). In contrast to the prevalent role of NMDARs in the adult brain, we found that both CP-AMPARs and LT-VGCCs mediated MeCP2 S421 and CaMKII T286 phosphorylation induced by kainic acid (KA) or high potassium chloride (KCl) stimulation. Furthermore, in vivo post-seizure treatment with the broad-spectrum AMPAR antagonist NBQX, the CP-AMPAR blocker IEM-1460, or the LT-VGCC antagonist nimodipine blocked seizure-induced MeCP2 phosphorylation. Collectively, these results demonstrate that early-life seizures dysregulate critical activity-dependent developmental signaling pathways, in part via CP-AMPAR and LT-VGCC activation, providing novel age-specific therapeutic targets for convergent pathways underlying epilepsy and ASDs.

Early-life seizures alter synaptic calcium-permeable AMPA receptor function and plasticity

Calcium (Ca²⁺)-mediated⁴ signaling pathways are critical to synaptic plasticity. In adults, the NMDA glutamate receptor (NMDAR) represents a major route for activity-dependent synaptic Ca²⁺ entry. However, during neonatal development, when synaptic plasticity is particularly high, many AMPA glutamate receptors (AMPARs) are also permeable to Ca²⁺ (CP-AMPAR) due to low GluA2 subunit expression, providing an additional route for activity- and glutamate-dependent Ca²⁺ influx and subsequent signaling. Therefore, altered hippocampal Ca²⁺ signaling may represent an age-specific pathogenic mechanism. We thus aimed to assess Ca²⁺ responses 48h after hypoxia-induced neonatal seizures (HS) in postnatal day (P)10 rats, a post-seizure time point at which we previously reported LTP attenuation. We found that Ca²⁺ responses were higher in brain slices from post-HS rats than in controls and that this increase was CP-AMPAR-dependent. To determine whether synaptic CP-AMPAR expression was also altered post-HS, we assessed the expression of GluA2 at hippocampal synapses and the expression of long-term depression (LTD), which has been linked to the presence of synaptic GluA2. Here we report a decrease 48h after HS in synaptic GluA2 expression at synapses and LTD in hippocampal CA1. Given the potentially critical role of AMPAR trafficking in disease progression, we aimed to establish whether post-seizure in vivo AMPAR antagonist treatment prevented the enhanced Ca²⁺ responses, changes in GluA2 synaptic expression, and diminished LTD. We found that NBQX treatment prevents all three of these post-seizure consequences, further supporting a critical role for AMPARs as an age-specific therapeutic target.

Epilepsy after neonatal seizures: literature review

INTRODUCTION

Acute neonatal seizures are the most frequent neurological complication in the neonatal intensive care units and the seizing newborns have an increased risk of long-term morbidity. However, the relationship between neonatal seizures and the development of epilepsy later in life is still unclear.

METHODS

We performed a literature review using the search terms "neonatal seizures AND outcome", "neonatal seizures AND epilepsy", "neonatal seizures AND post-neonatal epilepsy", including secondary sources of data such as reference lists of articles reviewed. From the studies in which data were available, the incidence of epilepsy was calculated by dividing the number of all subjects who developed epilepsy in the different studies considered with the number of all newborns enrolled to the studies less the number of patients lost at follow-up.

RESULTS

We found 44 studies published between 1954 and 2013, of which 4 were population-based studies and the remaining were hospital-based case series. The overall population evaluated was 4538 newborns and 17.9% developed post-neonatal epilepsy, with an onset within the first year of life in 68.5% of the patients. In 80.7%, epilepsy was associated with other neurological impairments.

CONCLUSION

Estimates on epilepsy after neonatal seizures vary widely depending on selection criteria and length of the follow-up. However, it represents a common outcome of these newborns, especially in those with severe brain injury and additional neurodevelopmental disabilities.

Neonatal seizures: treatment practices among term and preterm infants

Neonatal seizures are common clinical conditions in both term and preterm neonates, yet no clinical management guidelines for direct care exist. We surveyed 193 international neurologists, neonatologists, and specialists in neonatal neurology or neonatal neurocritical care to assess management practices for seizures in preterm and term neonates. We found high reported rates of electroencephalogram and amplitude-integrated electroencephalogram (aEEG) monitoring to detect neonatal seizures, prevalent use of older anticonvulsant agents, and high rates of neuroimaging. Overall, responses were similar for term and preterm neonates. However, term neonates were likelier to be more heavily investigated, with higher use of magnetic resonance imaging and of electroencephalogram and aEEG monitoring of at-risk neonates. Continuous monitoring and cranial imaging of neonatal seizures now comprise the standard of care in many centers, although management practices vary widely. Early recognition and management of neonatal seizures and possible underlying injury may lead to increased opportunities for stopping seizures, protecting the brain, and improving developmental outcomes in at-risk neonates. The need for collaboration among neonatologists and neurologists is urgent, to address gaps in knowledge regarding management of neonatal seizures in term and preterm neonates.

Topiramate for the treatment of neonatal seizures

Therapeutic options for treating neonatal seizures, such as phenobarbital and phenytoin, lack efficacy and are potentially harmful to the developing brain. Topiramate appears effective as both an antiseizure and neuroprotective agent in animal models of newborn brain injury. Although topiramate is a common add-on agent in newborns, its use in this population has not yet been reported. We performed a retrospective cohort study of clinical topiramate use in newborns with acute symptomatic seizures that were refractory to standard agents. In four of six newborns, apparent reduction or no further seizures occurred. None of the children experienced side effects resulting in discontinuation of the drug, either during the hospital admission or after discharge. Prospective studies evaluating the safety and efficacy of topiramate for both seizures and neuroprotection will be important in determining whether it deserves widespread use in clinical practice.

Induction of labor and cerebral palsy: a population-based study in Norway

OBJECTIVE

To investigate the association between labor induction and later development of cerebral palsy (CP).

DESIGN

Registry-based cohort study.

SETTING

Perinatal data on all children born in Norway 1996-1998 were obtained from the Medical Birth Registry of Norway (MBRN). Neurodevelopmental data were collected from the Norwegian Cerebral Palsy Registry (CPRN).

POPULATION

A total of 176,591 children surviving the neonatal period. Of 373 children with CP, detailed data were available on 241.

METHODS

Unadjusted and adjusted odds ratios (OR) with 95% confidence intervals (CI) were calculated as estimates of the relative risk that a child with CP was born after labor induction.

MAIN OUTCOME MEASURES

Total CP and spastic CP subtypes.

RESULTS

Bilateral cerebral palsy was more frequently observed after induced labor (OR: 3.1; 95% CI 2.1-4.5). For children born at term the association between bilateral CP and labor induction was stronger (OR: 4.4; 95% CI 2.3-8.6). The association persisted after adjustment for maternal disease, gestational age, standard deviation score for birthweight (z-score) and prelabor rupture of membranes (PROM) (adjusted OR: 3.7; 95%CI 1.8-7.5). Among children with CP born at term, four-limb involvement (quadriplegia) was significantly more frequent after induced (45.5%) compared with non-induced labor (8.0%). There was no significant association between labor induction and unilateral CP subtype or CP in preterm born children.

CONCLUSIONS

In this study population, we found that labor induction at term was associated with excess risk of bilateral spastic CP and in particular CP with four-limb involvement.

Clinical Neonatal Seizures are Independently Associated with Outcome in Infants at Risk for Hypoxic-Ischemic Brain Injury

OBJECTIVE

To examine whether neonatal seizures are associated with neurodevelopmental outcomes in infants with hypoxia-ischemia independent of the presence and severity of brain injury seen on magnetic resonance imaging (MRI).

STUDY DESIGN

We used multivariate regression to examine the independent effect of clinical neonatal seizures and their treatment on neurodevelopment in 77 term newborns at risk for hypoxic-ischemic brain injury. Clinical seizures were recorded prospectively, and high-resolution newborn MRI measured the severity of brain injury. The outcome measure was the Full-Scale Intelligence Quotient (FSIQ) of the Wechsler Preschool and Primary Scale of Intelligence-Revised and neuromotor score at age 4 years.

RESULTS

After controlling for severity of injury on MRI, the children with neonatal seizures had worse motor and cognitive outcomes compared with those without seizures. The magnitude of effect varied with seizure severity; children with severe seizures had a lower FSIQ than those with mild/moderate seizures (P < .0001).

CONCLUSIONS

Clinical neonatal seizures in the setting of birth asphyxia are associated with worse neurodevelopmental outcome, independent of the severity of hypoxic-ischemic brain injury. Randomized controlled trials are needed to determine whether differences in seizure treatment can improve outcome.

Controversies in neonatal seizure management

Seizures in the newborn period are common and frequently indicate serious underlying brain injury. Although accumulating evidence suggests that they may impair brain development, there are currently no evidence-based guidelines for evaluation and management of neonatal seizures. In this review, we will address some of the current controversies facing child neurologists and neonatologists, including how to define, monitor, and treat neonatal seizures.

Antenatal and intrapartum risk factors for seizures in term newborns: a population-based study, California 1998-2002

OBJECTIVE

To assess antenatal and intrapartum risk factors for seizures occurring during the birth admission.

STUDY DESIGN

Using multivariable logistic regression analysis, we evaluated the association between maternal characteristics and birth admission seizures in a cohort of 2.3 million California children born at >or=36 weeks' gestation between 1998 and 2002 using the California Office of Statewide Planning and Development database containing birth certificates linked to infant and maternal hospital discharge abstracts.

RESULTS

The incidence of seizures during the birth admission was 0.95/1000 live births. In an adjusted analysis, infants of women age 40 years and older who were nulliparous; had diabetes mellitus, intrapartum fever, or infection or delivered at >or=42 weeks had an increased risk of seizures. Infants of Hispanic and Asian mothers had a lower risk compared with infants of Caucasian mothers.

CONCLUSIONS

Several maternal antenatal and intrapartum factors increased the risk of seizures during the birth admission. Identifying and avoiding risks for neonatal seizures may lead to lower infant neurologic morbidity and mortality.

Maternal risk factors for term neonatal seizures: population-based study in Colorado, 1989-2003

Neonatal seizures in term infants are rare but have important potential implications for brain development. Risk factors for neonatal seizures in term infants have been less well defined than those among preterm infants. To evaluate the relationship between maternal risk factors and neonatal seizures in the first 72 hours of life in term infants, a case-control study using the Colorado Birth Certificate Registry was conducted. Term neonates in all hospitals in Colorado with and without seizures in the first 72 hours were studied. After adjusting for vaginal delivery in the setting of herpes infection and post-term delivery, preexisting diabetes in the mother (odds ratio 4.30, 95% confidence interval 1.64-11.27, P < .01) and fetal distress (odds ratio 5.88, 95% confidence interval 4.60-7.13, P < .0001) were independent risk factors for neonatal seizures in term infants. These findings are confirmatory of previous reports that maternal preexisting diabetes and fetal distress increase the risk of neonatal seizure in term infants. Although we cannot establish the pathophysiology of neonatal seizures from this analysis, hypoxic-ischemic brain injury and hypoglycemia in infants of diabetic mothers are known causes of neonatal seizures that can be represented in this analysis by fetal distress and maternal preexisting diabetes, respectively. Maternal diabetic vasculopathy can also be a contributing factor.

Early-onset neonatal seizures: types, risk factors and short-term outcome

In a large majority of term newborns, early-onset neonatal seizures (EONS) are believed to relate to perinatal risk factors.

AIM

To identify risk factors for EONS.

METHODS

Among a cohort of 1293 newborns admitted over a period of 2 years to the neonatal intensive care unit of Tikur Anbasa Hospital, Addis Ababa, 93 had seizures. The case control study method was used to identify risk factors associated with EONS. Univariate analysis was used to further examine risk factors after adjusting for the effect of severe perinatal asphyxia (Apgar < or = 3).

RESULTS

A total of 78 (85%) term newborns had EONS. Hypoxic-ischaemic encephalopathy (OR 3.46, 95% CI 2.74-7.42) and shock (OR 2.53, 95% CI 1.51-4.76) were significantly associated with EONS. Multifocal clonic (66%) followed by focal clonic (22%) were the most common types of EONS. Nine (11%) of the newborns with EONS died. During follow-up, 37 (53%) of the 69 surviving newborns with EONS had psychomotor delay with or without neurological deficit.

CONCLUSION

Hypoxic-ischaemic encephalopathy and shock are important causes of EONS.

Encephalopathy as a predictor of magnetic resonance imaging abnormalities in asphyxiated newborns

Basal ganglia abnormalities on magnetic resonance imaging predict neurodevelopmental impairment in newborns with perinatal depression. We determined the value of a clinical encephalopathy score as a predictor of abnormal magnetic resonance imaging results in newborns with perinatal depression. We assigned a neonatal encephalopathy score to 101 newborns. The encephalopathy score, based on alertness, feeding, tone, respiratory status, reflexes, and seizure activity, was assigned once daily. The maximum score from the first 3 days of life was compared with abnormal magnetic resonance imaging results present globally or solely in the basal ganglia.Eighty-one percent of patients manifested abnormalities on any magnetic resonance imaging sequence, and 37% manifested abnormalities in the basal ganglia alone. The encephalopathy score correlated well with magnetic resonance imaging abnormalities in the basal ganglia (Spearman Rho = 0.335, P < 0.0001). Newborns with mild and severe encephalopathy had likelihood ratios of 0.41 and 7.4, respectively, for abnormal basal ganglia magnetic resonance imaging results. Newborns with moderate encephalopathy (composing 47% of the cohort) manifested basal ganglia abnormalities with a likelihood ratio of 0.785. Severe clinical encephalopathy correlates with abnormal basal ganglia magnetic resonance imaging results, and mild encephalopathy correlates with a normal magnetic resonance imaging result. However, standard clinical criteria do not alter the prior risk of abnormal basal ganglia magnetic resonance imaging results for newborns with moderate encephalopathy.

Demographic and intrapartum characteristics of term pregnancies with early-onset neonatal seizures

OBJECTIVE

To compare the demographic and intrapartum factors of term pregnancies in which early-onset neonatal seizures developed with the characteristics of a large, unselected control population.

STUDY DESIGN

Pregnancies delivered at term (gestational age > or = 37 weeks) in one birthing unit between 1984 and 1995 with a discharge diagnosis of neonatal seizures were identified. Maternal and neonatal charts of these patients were reviewed to confirm the diagnosis of early-onset seizure (EOS) which was defined as a clinical or EEG-diagnosed seizure within 72 hours of life. Demographic and intrapartum factors were compared between these EOS cases and all singleton term pregnancies delivered over the same time period in which there was no EOS. A regression model was then developed to determine factors predictive of EOS.

RESULTS

Of 80,561 total deliveries during the 11-year study period, there were 64,340 control and 62 EOS (0.1%) deliveries. Regression modeling identified NICU admission, depressed 1- and 5-minute Apgar scores, and neonatal intubation as predictors of EOS, but not operative vaginal, vaginal breech, or cesarean delivery.

CONCLUSION

Depressed condition at birth and/or the requirement for NICU care was the most important risk associated with early seizures in term infants.

The physiology of fetal heart rate patterns and perinatal asphyxia

The purpose of electronic fetal heart rate (FHR) monitoring is the ongoing assessment of fetal oxygenation. FHR tracings are analyzed for characteristic patterns that signify specific hypoxic or nonhypoxic events. A working knowledge of fetal physiology and the fetal response to hypoxia can aid and refine clinical interpretation of FHR patterns during labor. This article reviews the fetal response to decreased oxygenation, the physiology of subsequent FHR patterns and the clinical presentation of asphyxia in the newborn.

Intrapartum fever and unexplained seizures in term infants

OBJECTIVE

Early-onset neonatal seizures are a strong predictor of later morbidity and mortality in term infants. Although an association of noninfectious intrapartum fever with neonatal seizures in term infants has been reported, it was based on only a small number of neonates with seizures. We therefore conducted a case control study to investigate this association further.

METHODS

All term infants with neonatal seizures born at Brigham and Women's Hospital between 1989 and 1996 were identified. For this study, cases consisted of all term neonates with a confirmed diagnosis of seizure born after a trial of labor for whom no proximal cause of seizure could be identified. Infants with sepsis or meningitis were excluded. Four controls matched by parity and date of birth were identified for each case. The rate of intrapartum maternal temperature >100.4 degrees F was compared for case infants and controls. Potential confounding was controlled in logistic regression analysis.

RESULTS

Cases comprised 38 term infants with unexplained seizures after a trial of labor. We identified 152 controls. Infants with seizures were more likely to be born to mothers who were febrile during labor (31.6% vs 9.2%). In almost all cases, the fever developed during labor (94.7% cases, 97.4% controls). At admission, mothers of infants with seizures were not significantly more likely to have factors associated with concern about infection such as a white blood cell count >15 000/mm(3) (28. 9% vs 19.1%) and premature rupture of the membranes (15.8% vs 17.8%). In a logistic regression analysis controlling for confounding factors, intrapartum fever was associated with a 3.4-fold increase in the risk of unexplained neonatal seizures (odds ratio = 3.4, 95% confidence interval = 1.03-10.9).

CONCLUSION

Our data indicate that intrapartum fever, even when unlikely to be caused by infection, is associated with a fourfold increase in the risk of unexplained, early-onset seizures in term infants.

Does asphyxia cause cerebral palsy?

The incidence of cerebral palsy is 1 per 1,000, whereas the proportion caused by perinatal asphyxia is only 8% to 10%. The purpose of this article is to review the relationship between asphyxia and cerebral palsy. Only a minority of cases, those involving severe pathological fetal academia, are consistently associated with neonatal encephalopathy and an increased risk of cerebral palsy.

The relationship between nucleated red blood cell counts and early-onset neonatal seizures

OBJECTIVE

This study was undertaken to better define the timing of neurologic insult in neonates with early-onset seizures through evaluation of neonatal nucleated red blood cell levels.

STUDY DESIGN

Medical records and the International Classification of Diseases, Ninth Revision codes were used to identify all term neonates with neonatal convulsions who were delivered at our institution (January 1, 1990-December 31, 1995). Each neonate with early-onset seizures was matched to the next 3 neonates who met the following criteria: gestational age > or =37 weeks, no early-onset seizures, birth weight > or =800 g, umbilical artery pH > or =7.25, and a 5-minute Apgar score >7. Demographic characteristics, clinical factors, and mean initial nucleated red blood cell counts were compared between groups.

RESULTS

During the 6-year study period, there were a total of 36, 490 singleton term deliveries of infants who were alive at birth. Forty-five (0.1%) of these neonates had early-onset seizures. Thirty neonates with early-onset seizures met the inclusion criteria. Mean nucleated red blood cell counts (number of nucleated red blood cells per 100 white blood cells) for neonates with early-onset seizures were significantly increased compared with those of control neonates (18.4 +/- 22.0 vs 4.6 +/- 4.5; P <.0008).

CONCLUSIONS

Our findings are suggestive of the hypothesis that neurologic injury leading to early-onset seizures often occurs before the intrapartum period.

Risk factors for neonatal encephalopathy in Kathmandu, Nepal, a developing country: unmatched case-control study

OBJECTIVE

To determine the risk factors for neonatal encephalopathy among term infants in a developing country.

DESIGN

Unmatched case-control study.

SETTING

Principal maternity hospital of Kathmandu, Nepal.

SUBJECTS

All 131 infants with neonatal encephalopathy from a population of 21 609 infants born over an 18 month period, and 635 unmatched infants systematically recruited over 12 months.

MAIN OUTCOME MEASURES

Adjusted odds ratio estimates for antepartum and intrapartum risk factors.

RESULTS

The prevalence of neonatal encephalopathy was 6.1 per 1,000 live births of which 63% were infants with moderate or severe encephalopathy. The risk of death from neonatal encephalopathy was 31%. The risk of neonatal encephalopathy increased with increasing maternal age and decreasing maternal height. Antepartum risk factors included primiparity (odds ratio 2.0) and non-attendance for antenatal care (2.1). Multiple births were at greatly increased risk (22). Intrapartum risk factors included non-cephalic presentation (3.4), prolonged rupture of membranes (3.8), and various other complications. Particulate meconium was strongly associated with encephalopathy (18). Induction of labour with oxytocin was associated with encephalopathy in 12 of 41 deliveries (5.7). Overall, 78 affected infants (60%) compared with 36 controls (6%) either had evidence of intrapartum compromise or were born after an intrapartum difficulty likely to result in fetal compromise. A concentration of maternal haemoglobin of less than 8.0 g/dl in the puerperium was significantly associated with encephalopathy (2.5) as was a maternal thyroid stimulating hormone concentration greater than 5 mIU/l (2.1).

CONCLUSIONS

Intrapartum risk factors remain important for neonatal encephalopathy in developing countries. There is some evidence of a protective effect from antenatal care. The use of oxytocin in low income countries where intrapartum monitoring is suboptimal presents a major risk to the fetus. More work is required to explore the association between maternal deficiency states and neonatal encephalopathy.

Intrapartum maternal fever and neonatal outcome

OBJECTIVE

Much of fever during term labor may not be infectious but rather a consequence of the use of epidural analgesia. Therefore, we investigated the association of elevated maternal intrapartum temperature with neonatal outcome when the infant does not develop an infection.

METHODS

We studied 1218 nulliparous women with singleton, term pregnancies in a vertex presentation and spontaneous labor. Women were excluded if their temperature was >99.5 degrees F at admission for delivery, if they were diabetic or had an active genital herpes infection or if their infant developed a neonatal infection, had a congenital infection, or had a major malformation. Maximum intrapartum temperature was categorized as: </=100.4 degrees F (afebrile), 100.5 degrees F to 101 degrees F, and >101 degrees F.

RESULTS

During labor, 123 women (10.1%) developed a fever >100.4 degrees F; 62 (5.1%) women had a maximum temperature of 100.5 degrees F to 101 degrees F and 61 (5.0%) women had a maximum temperature >101 degrees F. Of febrile women, 97.6% had received epidural analgesia for pain relief. Infants of women developing a fever >100.4 degrees F were more likely to have a 1-minute Apgar score <7 (22.8% for >100.4 degrees F vs 8.0% for afebrile) and to be hypotonic after delivery (4.8% for >100.4 degrees F vs.5% for afebrile). Compared with infants of afebrile women, infants whose mothers' maximum temperature was >101 degrees F were more likely to require bag and mask resuscitation (11.5% vs 3.0%) and to be given oxygen therapy in the nursery (8.2% vs 1.3%). We also found a higher rate of neonatal seizure with fever (3.3% vs.2%), but the number of infants with seizure was small (n = 4). All associations remained essentially the same after controlling for confounding in logistic regression analyses.

CONCLUSIONS

Intrapartum maternal fever, particularly if >101 degrees F, was associated with a number of apparently transient adverse effects in the newborn. Larger studies are needed to investigate the association of intrapartum fever with neonatal seizures and to determine whether any lasting injury to the fetus may occur.

A risk model approach to the prediction of fetal acidemia

Known risk factors for adverse perinatal outcome were related to severe fetal acidemia during labor and at birth. Severe fetal acidemia was defined as a fetal scalp or umbilical artery pH > 3 SD below the mean for normal pregnancy. pH values were available for 1,524 singleton births without congenital anomalies. Of these births, 83 (5.4%) had at least one pH value > 3 SD below the reference mean. Known risk factors in the group with severe acidemia were compared with those in a random sample of the remaining 94.6% births. The strongest predictor of severe fetal acidemia was an abnormal cardiotocogram with a Hammacher score > 8. Risk factors shown to lower pH values significantly were combined in a prediction model based on multiple regression analysis. Back-validation of the model showed that half of all cases of severe fetal acidemia could not be adequately predicted. It is concluded that such prediction models do not contribute to a more effective detection of severe fetal acidemia.

Does the onset of neonatal seizures correlate with the timing of fetal neurologic injury?

The onset of seizures after birth has been considered evidence of an intrapartum asphyxial event. The present study was undertaken to determine whether the timing of neonatal seizures after birth correlated with the timing of a fetal asphyxial event. Thus, singleton term infants diagnosed with hypoxic ischemic encephalopathy and permanent brain injury had a mean birth to seizure onset interval of 9.8 +/- 17.7 (range 1-90) hours. When these infants were categorized according to their fetal heart rate (FHR) patterns, the acute group (normal FHR followed by a sudden prolonged FHR deceleration that continued until delivery) tended to have earlier seizures than infants did within the tachycardia group (normal FHR followed by tachycardia, repetitive decelerations, and diminished variability) and the preadmission group (persistent nonreactive FHR pattern intrapartum). These seizure intervals were as follows: acute, 6.6 +/- 18.0 (range 1-90) hours; tachycardia, 11.1 +/- 17.1 (range 1-61) hours; and preadmission, 11.8 +/- 17.9 (range 1-79) hours (p < 0.05). But the range varied widely and no group was categorically distinct. In conclusion, the onset of neonatal seizures after birth does not, in and of itself, appear to be a reliable indicator of the timing of fetal neurologic injury.

Bilateral spastic cerebral palsy--a collaborative study between southwest Germany and western Sweden. III: Aetiology

In this third report from the collaborative study of children with bilateral spastic cerebral palsy born between 1975 and 1986, aetiology was analysed. Evidence for a prenatal aetiology increased with gestational age, whereas evidence for a peri-/neonatal aetiology decreased. The largest subgroup, the leg-dominated subtype, showed the same distribution of aetiology as the total group. A prenatal aetiology was found mainly among term and moderately preterm children with a four-limb-dominated subtype; a peri-/neonatal aetiology among very preterm children with a three- or four-limb-dominated subtype or among term children with a dyskinetic-spastic subtype. The findings support the hypothesis generated from the authors' epidemiological results of a peri-/neonatal aetiology being predominant among preterm, and a prenatal aetiology among term, children with bilateral spastic cerebral palsy.

Clustering of perinatal markers of birth asphyxia and outcome at age five years

OBJECTIVES

In a cohort of term infants with cerebral depression at delivery, to investigate the association of perinatal signs of birth asphyxia, particularly abnormal fetal heart rate patterns in labour, acidaemia, and serious neonatal encephalopathy, with neurodevelopmental outcome at age five years.

DESIGN

Five year follow up study of a birth cohort.

SETTING

Regional maternity hospital.

SUBJECTS

One hundred and eighty-four singleton infants with a 1 min Apgar score < or = 3, born at term between January 1984 and September 1985.

MAIN OUTCOME MEASURES

Neonatal death, cerebral palsy, and scores on a battery of neurodevelopmental tests at age five.

RESULTS

Seven infants had a cluster of perinatal signs suggestive of birth asphyxia; all included serious neonatal encephalopathy. Three of these infants died neonatally, three had spastic quadriparesis with profound developmental delay, and one was unimpaired at the age of five. Among the remaining infants, no association was found between severely abnormal fetal heart rate patterns in labour and scores on neurodevelopmental tests, or between acid-base status at delivery and test scores.

CONCLUSIONS

Birth asphyxia, identified by a cluster of abnormal perinatal signs, including serious neonatal encephalopathy, has a poor prognosis. If serious encephalopathy is not present, cerebral depression at birth preceded by abnormal fetal heart rate patterns in labour, or with acid-base derangement, is not predictive of later impairment.

Cerebral palsy and neonatal encephalopathy

A retrospective cohort study was carried out to test the hypothesis that children born at term with cerebral palsy with signs of neurological dysfunction preceded by depression at birth (termed neonatal encephalopathy) differ from those without such signs in the frequency of antenatal and perinatal factors, and in the severity and characteristics of their impairment and disability. The study was carried out in the area covered by Oxford Regional Health Authority. Antenatal, intrapartum, neonatal factors, and the later clinical status of the two groups of children were used as the main outcome measures. Although most maternal and antenatal characteristics were similar in the two groups, the mothers of children with a history of neonatal encephalopathy were more likely to be primigravidae (odds ratio (OR) 2.0; 95% confidence interval (CI) 1.0 to 4.3) and to have a pregnancy of greater than 41 weeks' gestation (OR 3.5; 95% CI 1.0 to 12.1). Intrapartum complications were more frequent in the neonatal encephalopathy group: meconium staining of the amniotic fluid (OR 3.5; 95% CI 1.5 to 7.8), an ominous first stage cardiotocograph (OR 10.2; 95% CI 2.9 to 36.4), with a longer median duration of abnormality (200 v 48 minutes). At 5 years of age those with neonatal encephalopathy were more likely to have developed spastic quadriplegia (OR 4.8; 95% CI 2.2 to 10.5), to have visual impairment (OR 3.0; 95% CI 1.0 to 8.6), and to be non-walking (OR 4.0; 95% CI 1.8 to 8.8) than those without neonatal encephalopathy. Children with cerebral palsy who were born at term and have neonatal encephalopathy are more likely to have had signs of intrapartum asphyxia and are more likely to have a more severe form of cerebral palsy than those without a history of neonatal encephalopathy. Although this group represents only one in 10 of all cases of cerebral palsy, some of these may be obstetrically preventable.

Maternal-fetal HLA sharing and risk of newborn encephalopathy and seizures: a pilot study

A pilot case-control study was done to collect data on whether susceptibility to newborn encephalopathy and neonatal seizures is influenced by the degree of maternal-fetal sharing of HLA antigens. Cases included 13 infants with moderate or severe newborn encephalopathy and seven infants with neonatal seizures but no other signs of encephalopathy. Controls were neurologically normal infants matched to cases by date of birth, sex, race, and payment status. Infants and their mothers were typed for HLA-A, -B, -DR, and -DQ antigens. The observed frequency of sharing of maternal antigens was greater than expected (ie, 0.5) for cases compared to controls at the HLA-B, -DR, and -DQ loci but not for HLA-A. The risk of neurologic problems in the neonatal period was increased 6.3 times when there was more than one match at the HLA-DR or -DQ locus. Placental abnormalities were noted at delivery only among cases, and the mean placental weight in cases was 598 g versus 695 g in controls. Further studies with sample sizes sufficiently large to statistically test this hypothesis are needed.

The paradox of electronic fetal monitoring: more data may not enable us to predict or prevent infant neurologic morbidity

Electronic fetal heart rate monitoring has been used to identify periods of fetal risk, with the hope that clinical intervention would avoid the potential for perinatal death or neurologic damage. A literature review of 10 infant studies failed to document fetal heart rate patterns associated with neurologic injury or protocols for intervention to avoid neurologic injury. A separate analysis of fetal heart rate patterns from 55 brain-damaged infants failed to find consistent patterns that foreshadowed the observed brain injury. These findings should not be surprising, because the majority of infant brain damage occurs outside the intrapartum period and because electronic monitoring may identify times of fetal risk but was never expected to identify brain damage.

Falling incidence of hypoxic-ischaemic encephalopathy in term infants

OBJECTIVE

To examine trends in the incidence of hypoxic-ischaemic encephalopathy over a 13-year period.

DESIGN

A retrospective analysis of medical records of all infants admitted in the years 1976-1980 and 1984-1988.

SETTING

A large non-teaching district health authority in central England.

SUBJECTS

Infants admitted to a district general hospital neonatal unit with clinical features of hypoxic-ischaemic encephalopathy.

MAIN OUTCOME MEASURES

Incidence of three grades of hypoxic-ischaemic encephalopathy, handicap and mortality.

RESULTS

During the first 5-year period the overall incidence of hypoxic-ischaemic encephalopathy was 7.7 per 1000 live births with 2.6 per 1000 live births being severely affected (grades II and III). In the second 5-year period the overall incidence was 4.6 per 1000 live births with 1.8 per 1000 live births being severely affected. The difference in the overall rate is statistically significant. Of the infants with severe encephalopathy 61% had Apgar scores below 4 at 1 min and 60% were born by instrumental or operative delivery.

CONCLUSIONS

The fall in incidence of hypoxic-ischaemic encephalopathy has occurred during a period of falling perinatal mortality rate. It was instructive to find that infants born vaginally and without obstetric intervention formed a larger fraction of the severely affected infants in the later period.

Fetal acidosis in labour: a prospective study on the effect of parity

The effect of parity on intrapartum fetal scalp pH was investigated in 6466 patients in labour with a live fetus who were delivered in 1987. 350 (5.4%) required fetal scalp blood sampling for pH (FBS), 236 primigravidae (10.4%) and 114 multigravidae (2.7%) (P less than 0.001). Fetal acidosis (pH less than 7.20) was detected in 35 patients, 27 primigravidae (11.4%) and 8 multigravidae (7.0%) (P less than 0.001). The incidence of intrapartum acidosis in the 2275 primigravidae and the 4191 multigravidae was 1.2 and 0.2% respectively (P less than 0.001). The two deaths from birth asphyxia and three cases of neonatal seizures occurred in primigravidae. In primigravidae requiring FBS, fetal acidosis was not associated with the use of oxytocin or with increased duration of labour. Neonatal seizures were more common overall in primigravidae than in multigravidae and more common in patients requiring FBS than in those not requiring FBS (P less than 0.05). The higher incidence of FBS, fetal scalp acidosis and neonatal seizures in primigravidae has important implications for intrapartum fetal monitoring.

The second stage of labour: durational dilemmas

The optimal management of prolonged second stage of labour remains a confused area of thought and action. This confusion is particularly evident when epidural analgesia is also being used. A review of the literature indicates that prolonged duration of the second stage, i.e. from full dilation of the cervix until delivery, with or without epidural analgesia, has little adverse effect on perinatal outcome. More attention should be paid to the expulsive phase of the second stage and greater efforts made to reduce unnecessary interventions.

The work of the National Perinatal Epidemiology Unit. One example of technology assessment in perinatal care

This article describes one approach to assessing the effects of perinatal care--that adopted by the National Perinatal Epidemiology Unit in Oxford, England. The unit's research has been based primarily on a combination of simple, descriptive analyses of observational data and statistically robust analyses of evidence derived from randomized controlled trials.

Predicting neonatal morbidity after perinatal asphyxia: a scoring system

Predicting immediate neonatal morbidity after perinatal asphyxia has been difficult. A review of asphyxiated neonates greater than or equal to 36 weeks' gestation admitted to The Children's Hospital Newborn Intensive Care Unit in 1983 was conducted to devise a scoring system that would rapidly predict organ dysfunction observed in the immediate neonatal period. Comparison of potential score components to morbidity by multiple regression analysis yielded significant association with abnormalities in fetal heart rate monitoring, the 5-minute Apgar score, and neonatal base deficit. A scoring system was devised whose sensitivity (93.8%) and specificity (81.3%) were more predictive than any of its individual components. Prospective analysis in a similar population in 1984 validated its ability to distinguish severe from moderate morbidity after asphyxia. Positive predictive value for the score in the combined study groups (n = 98) was 79% and the negative predictive value was 83%. The scoring system may offer a rapid and accurate prediction of organ dysfunction in the immediate neonatal period after asphyxia.

Cerebral palsy among children born during the Dublin randomised trial of intrapartum monitoring

In a randomised trial involving 13,079 liveborn children intrapartum care by electronic fetal heart rate monitoring, with scalp blood sampling when indicated, was associated with a 55% reduction in neonatal seizures. Reassessment, when aged 4, of the 9 children in the intensively monitored group and 21 in the control group who survived after neonatal seizures showed that 3 such children in each group had cerebral palsy. A fourth child in the intensively monitored group with cerebral palsy had had transient abnormal neurological signs during the neonatal period. 8 other children in the intensively monitored group and 7 in the control group who had not had abnormal neurological signs in the neonatal period also had cerebral palsy. 16 (78%) of the total of 22 cases of cerebral palsy had not shown clinical signs suggestive of intrapartum asphyxia. Thus, compared with intermittent intrapartum monitoring, intensive monitoring has little, if any, protective effect against cerebral palsy.