Sudden Unexpected Death in Fetal Life Through Early Childhood

Screening for viral pathogens in the gastrointestinal tract from cases of sudden unexpected death in infancy at the Tygerberg Medico-legal Mortuary

Sudden and unexpected death in infancy (SUDI) may be triggered by an external risk or exposure. Intestinal infections with enteric viruses may disrupt the gut and enhance bacterial toxins present in SUDI cases. While diarrhoeal disease deaths have decreased worldwide, approximately half a million deaths still occur in children in Sub- Saharan Africa and South Asia. Furthermore, the role of viral enteropathogens in SUDI cases have not been investigated. The aim of this study was to describe specific viral pathogens in stool samples collected from SUDI cases and age-matched, apparently healthy infants in Cape Town, South Africa. Stool samples were collected from 176 SUDI cases between June 2017 and May 2018. In addition, stool samples were collected from the nappies of 30 age-matched, apparently healthy infants as a control group. Real-time polymerase chain reaction was performed on the stool samples for viral detection. A total of 111 SUDI cases were positive for viruses, with rotavirus (38.6%; 68/176) and norovirus GI and GII (30.0%; 53/176) were prevalent in SUDI cases. Adenovirus Type F was present in only 15.9% (28/176), astrovirus in 9.7% (17/176), and sapovirus in 0.6% (1/176) of cases. In the control samples, norovirus GII was detected most frequently (36.7%; 11/30), followed by rotavirus (33.3%; 10/30), and sapovirus in 6.7% (2/30). While there was no significant association between SUDI cases and enteric viruses, the majority of viruses were significantly associated with the seasons. The study confirms the importance of rotavirus vaccination and describes the significance of norovirus infection in children, post rotavirus vaccine introduction.

Sudden Infant Death Syndrome: Risk Factors and Newer Risk Reduction Strategies

Sudden infant death syndrome (SIDS) continues to be one of the top causes of infant death in the U.S. Despite significant public health initiatives focused on high-risk populations to enhance sleep environments and techniques. The SIDS rate has remained stable in recent years. Risk factors and newer risk reduction strategies for SIDS are the focus of this review article. We conducted a comprehensive literature search on Medline, Cochrane, Embase, and Google Scholar until July 2022. The following search strings and Medical Subject Heading (MeSH) terms were used: "SIDS," "Sudden Infant Death" and "SUID". We explored the literature on SIDS for its epidemiology, pathophysiology, the role of various etiologies and their influence, associated complications leading to SIDS, and preventive and treatment modalities. Despite a more than 50% drop-in rates since the start of the "Back to Sleep" campaign in 1994, sudden infant death syndrome (SIDS) continues to be the top cause of post-neonatal mortality in the United States, despite continued educational initiatives that support safe sleep and other risk reduction strategies. The new American Academy of Pediatrics guidelines for lowering the risk of SIDS include a lot of emphasis on sleeping habits, bedding, and environment but also include elements that are frequently ignored (i.e., prenatal care, smoking, alcohol and drug use, and childhood vaccinations). This study highlights these less-frequently discussed aspects and identifies treatments that have produced beneficial behavioral shifts that benefit newborns as well as their mothers' health and wellbeing.

Copy Number Variation and Structural Genomic Findings in 116 Cases of Sudden Unexplained Death between 1 and 28 Months of Age

In sudden unexplained death in pediatrics (SUDP) the cause of death is unknown despite an autopsy and investigation. The role of copy number variations (CNVs) in SUDP has not been well-studied. Chromosomal microarray (CMA) data are generated for 116 SUDP cases with age at death between 1 and 28 months. CNVs are classified using the American College of Medical Genetics and Genomics guidelines and CNVs in our cohort are compared to an autism spectrum disorder (ASD) cohort, and to a control cohort. Pathogenic CNVs are identified in 5 of 116 cases (4.3%). Variants of uncertain significance (VUS) favoring pathogenic CNVs are identified in 9 cases (7.8%). Several CNVs are associated with neurodevelopmental phenotypes including seizures, ASD, developmental delay, and schizophrenia. The structural variant 47,XXY is identified in two cases (2/69 boys, 2.9%) not previously diagnosed with Klinefelter syndrome. Pathogenicity scores for deletions are significantly elevated in the SUDP cohort versus controls (p = 0.007) and are not significantly different from the ASD cohort. The finding of pathogenic or VUS favoring pathogenic CNVs, or structural variants, in 12.1% of cases, combined with the observation of higher pathogenicity scores for deletions in SUDP versus controls, suggests that CMA should be included in the genetic evaluation of SUDP.

Sudden unexpected infant death risk profiles in the first month of life

BACKGROUND

Limited improvement in current SUID rates requires further identification of its characteristics, including age-specific risk patterns.

OBJECTIVE

Compare SUID risk factors in the first week versus the remainder in the first month of life.

DESIGN/METHODS

We compared maternal and infant data from New Jersey databases for SUID from 2000 to 2015 in infants ≥ 34 weeks GA in the two groups.

RESULTS

In the period studied, 123 died in the first 27 days, 24 before seven. Deaths in the first week had a higher percentage of mothers with post-High School education (OR 3.50, CI: 1.38-8.87) and a primary Cesarean section delivery (OR 4.0, CI: 1.39-11.49), and a smaller percentage with inadequate prenatal care (OR 0.36, CI: 0.14, 0.94). A smaller percentage of first-week deaths had mothers who smoked during pregnancy or identified as Black, non-Hispanic, but these findings did not reach significance (p < .08 and p < .09, respectively).

CONCLUSIONS

SUID in the first week and the first month of life is rare. However, despite a limited sample size, data suggest that even within the first month of life, there are differences in risk patterns for SUID based on age at death. Age-specific profiles may lead to new hypotheses regarding causality and more refined risk-reduction guidelines and warrant further study.

Genetic Determinants of Sudden Unexpected Death in Pediatrics

PURPOSE

This study aimed to evaluate genetic contributions to sudden unexpected death in pediatrics (SUDP).

METHODS

We phenotyped and performed exome sequencing for 352 SUDP cases. We analyzed variants in 294 "SUDP genes" with mechanisms plausibly related to sudden death. In a subset of 73 cases with parental data (trios), we performed exome-wide analyses and conducted cohort-wide burden analyses.

RESULTS

In total, we identified likely contributory variants in 37 of 352 probands (11%). Analysis of SUDP genes identified pathogenic/likely pathogenic variants in 12 of 352 cases (SCN1A, DEPDC5 [2], GABRG2, SCN5A [2], TTN [2], MYBPC3, PLN, TNNI3, and PDHA1) and variants of unknown significance-favor-pathogenic in 17 of 352 cases. Exome-wide analyses of the 73 cases with family data additionally identified 4 de novo pathogenic/likely pathogenic variants (SCN1A [2], ANKRD1, and BRPF1) and 4 de novo variants of unknown significance-favor-pathogenic. Comparing cases with controls, we demonstrated an excess burden of rare damaging SUDP gene variants (odds ratio, 2.94; 95% confidence interval, 2.37-4.21) and of exome-wide de novo variants in the subset of 73 with trio data (odds ratio, 3.13; 95% confidence interval, 1.91-5.16).

CONCLUSION

We provide strong evidence for a role of genetic factors in SUDP, involving both candidate genes and novel genes for SUDP and expanding phenotypes of disease genes not previously associated with sudden death.

Infant Mortality among Adolescent Mothers in the United States: A 5-Year Analysis of Racial and Ethnic Disparities

OBJECTIVE

This study was aimed to examine differences in infant mortality outcomes across maternal age subgroups less than 20 years in the United States with a specific focus on racial and ethnic disparities.

STUDY DESIGN

Using National Center for Health Statistics cohort-linked live birth-infant death files (2009-2013) in this cross-sectional study, we calculated descriptive statistics by age (<15, 15-17, and 18-19 years) and racial/ethnic subgroups (non-Hispanic white [NHW], non-Hispanic black [NHB], and Hispanic) for infant, neonatal, and postneonatal mortality. Adjusted odds ratios (aOR) were calculated by race/ethnicity and age. Preterm birth and other maternal characteristics were included as covariates.

RESULTS

Disparities were greatest for mothers <15 and NHB mothers. The risk of infant mortality among mothers <15 years compared to 18 to 19 years was higher regardless of race/ethnicity (NHW: aOR = 1.40, 95% confidence interval [CI]: 1.06-1.85; NHB: aOR = 1.28, 95% CI: 1.04-1.56; Hispanic: aOR = 1.36, 95%CI: 1.07-1.74). Compared to NHW mothers, NHB mothers had a consistently higher risk of infant mortality (15-17 years: aOR = 1.12, 95% CI: 1.03-1.21; 18-19 years: aOR = 1.21, 95% CI: 1.15-1.27), while Hispanic mothers had a consistently lower risk (15-17 years: aOR = 0.72, 95% CI: 0.66-0.78; 18-19 years: aOR = 0.74, 95% CI: 0.70-0.78). Adjusting for preterm birth had a greater influence than maternal characteristics on observed group differences in mortality. For neonatal and postneonatal mortality, patterns of disparities based on age and race/ethnicity differed from those of overall infant mortality.

CONCLUSION

Although infants born to younger mothers were at increased risk of mortality, variations by race/ethnicity and timing of death existed. When adjusted for preterm birth, differences in risk across age subgroups declined and, for some racial/ethnic groups, disappeared.

KEY POINTS

· Infant mortality risk was highest for adolescents <15 years old across racial/ethnic groups.. · Racial/ethnic disparities in timing of death were present even among the youngest adolescents.. · Infants of NHB adolescents had greatest risk of mortality, especially as age increased.. · Preterm birth influenced infant mortality risk, especially among NHB adolescents..

Sudden unexpected death in infancy: Severe pulmonary anatomopathological findings in spite of inconsistent clinical features

Respiratory tract infections play a considerable pathogenetic role in many cases of sudden infant death (SID). Frequently, clinicians encounter difficulties in diagnosing the disease because of its often unspecific clinical and radiological presentation. We report three cases of sudden unexpected death in infancy (SUDI), involving two males and one female admitted to hospital due to mild respiratory distress. In all three cases, complete post-mortem investigations were successful in uncovering interstitial lung disease as the cause of death. These cases highlight the key role of infection-related interstitial lung diseases in the pathogenesis of some currently unexplained SUDI/SIDS and the diagnostic difficulties due to the variable clinical and histological pattern, thereby explaining the importance of performing complete post-mortem investigations whenever an infant dies suddenly and unexpectedly.

Machine Learning Approaches to Determine Feature Importance for Predicting Infant Autopsy Outcome

INTRODUCTION

Sudden unexpected death in infancy (SUDI) represents the commonest presentation of postneonatal death. We explored whether machine learning could be used to derive data driven insights for prediction of infant autopsy outcome.

METHODS

A paediatric autopsy database containing >7,000 cases, with >300 variables, was analysed by examination stage and autopsy outcome classified as 'explained (medical cause of death identified)' or 'unexplained'. Decision tree, random forest, and gradient boosting models were iteratively trained and evaluated.

RESULTS

Data from 3,100 infant and young child (<2 years) autopsies were included. Naïve decision tree using external examination data had performance of 68% for predicting an explained death. Core data items were identified using model feature importance. The most effective model was XG Boost, with overall predictive performance of 80%, demonstrating age at death, and cardiovascular and respiratory histological findings as the most important variables associated with determining medical cause of death.

CONCLUSION

This study demonstrates feasibility of using machine-learning to evaluate component importance of complex medical procedures (paediatric autopsy) and highlights value of collecting routine clinical data according to defined standards. This approach can be applied to a range of clinical and operational healthcare scenarios.

Systematic review of ambient temperature exposure during pregnancy and stillbirth: Methods and evidence

BACKGROUND

Associations between ambient temperature exposure during pregnancy and stillbirth have been reviewed and described in the literature. However, there is no existing review of environmental and epidemiologic methods applied to measure stillbirths resulting from exposure to ambient temperatures during pregnancy. The objective of this study is to systematically review published methods, data sources, and data linkage practices to characterize associations between ambient temperature and stillbirth to inform stillbirth prevention and risk management strategies.

METHODS

A systematic review of published studies that assess the association between ambient temperature exposure during pregnancy using any measures or approach and stillbirth was undertaken in Cochrane Library, PubMed, Medline, Scopus, Embase, and Web of Science of studies (2000-2020, inclusive). Selection of studies were assessed by pre-specified eligibility criteria and documented using PRISMA. Citations were managed using EndNote X8 whilst selection, reviewing, and data extraction were performed using Covidence. The screening, selection, and data extraction process consisted of two blind, independent reviews followed by a tertiary independent review. An adapted Critical Appraisal Skills Program (CASP) checklist was used to assess quality and bias. The main findings and characteristics of all studies was extracted and summarized. Where appropriate, a meta-analysis will be performed for measures of association.

RESULTS

Among 538 original records, 12 eligible articles were identified that analysed associations between ambient temperature exposure and stillbirth for 42,848 stillbirths among 3.4 million births across seven countries. Varied definitions of stillbirth were reported based on gestational age, birthweight, both, or neither. The overall rate of stillbirth ranged from 1.9 to 38.4 per 1000 among six high-income countries and one low-middle-income country. All study designs were retrospective and included ten cohort studies, three case-crossover studies, and two additional case-control subgroup analysis. Exposure data for ambient temperature was mostly derived from standard municipal or country-level monitors based on weather stations (66.6%) or a forecasting model (16.7%); otherwise, not reported (16.7%). Results were not statistically pooled for a meta-analysis due to heterogeneity of methods and models among included studies. All studies reported associations of increased risk of stillbirth with ambient temperature exposures throughout pregnancy, particularly in late pregnancy. One study estimates 17-19% (PAR) of stillbirths are potentially attributable to chronic exposure to hot and cold ambient temperatures during pregnancy. Overall, risk of stillbirth was observed to increase below 15 °C and above 23.4 °C, where highest risk is above 29.4 °C.

CONCLUSION

Exposure to hot and cold temperatures during pregnancy may increase the risk of stillbirth, although a clear causative mechanism remains unknown. Despite lack of causal evidence, existing evidence across diverse settings observed similar effects of increased risk of stillbirth using a variety of statistical and methodological approaches for exposure assessments, exposure windows, and data linkage. Managing exposure to ambient temperatures during pregnancy could potentially decrease risk of stillbirth, particularly among women in low-resource settings where access to safe antenatal and obstetric care is challenging. To fully understand the effects or dose-response relationship of maternal exposure to ambient temperatures and stillbirth, future studies should focus on biological mechanisms and contributing factors in addition to improving measurement of ambient temperature exposure.

Sudden Infant Death Syndrome: Beyond Risk Factors

Sudden infant death syndrome (SIDS) is defined as "the sudden death of an infant under 1 year of age which remains unexplained after thorough investigation including a complete autopsy, death scene investigation, and detailed clinical and pathological review". A significant decrease of SIDS deaths occurred in the last decades in most countries after the beginning of national campaigns, mainly as a consequence of the implementation of risk reduction action mostly concentrating on the improvement of sleep conditions. Nevertheless, infant mortality from SIDS still remains unacceptably high. There is an urgent need to get insight into previously unexplored aspects of the brain system with a special focus on high-risk groups. SIDS pathogenesis is associated with a multifactorial condition that comprehends genetic, environmental and sociocultural factors. Effective prevention of SIDS requires multiple interventions from different fields. Developing brain susceptibility, intrinsic vulnerability and early identification of infants with high risk of SIDS represents a challenge. Progress in SIDS research appears to be fundamental to the ultimate aim of eradicating SIDS deaths. A complex model that combines different risk factor data from biomarkers and omic analysis may represent a tool to identify a SIDS risk profile in newborn settings. If high risk is detected, the infant may be referred for further investigations and follow ups. This review aims to illustrate the most recent discoveries from different fields, analyzing the neuroanatomical, genetic, metabolic, proteomic, environmental and sociocultural aspects related to SIDS.

Comprehensive Analysis of Genes Associated With Sudden Infant Death Syndrome

Background: Sudden infant death syndrome (SIDS) is a tragic incident which remains a mystery even after post-mortem investigation and thorough researches. Methods: This comprehensive review is based on the genes reported in the molecular autopsy studies conducted on SIDS so far. A total of 20 original studies and 7 case reports were identified and included in this analysis. The genes identified in children or adults were not included. Most of the genes reported in these studies belonged to cardiac channel and cardiomyopathy. Cardiac channel genes in SIDS were scrutinized for further analysis. Results: After screening and removing the duplicates, 42 unique genes were extracted. When the location of these genes was assessed, it was observed that most of these belonged to Chromosomes 11, 1 and 3 in sequential manner. The pathway analysis shows that these genes are involved in the regulation of heart rate, action potential, cardiac muscle cell contraction and heart contraction. The protein-protein interaction network was also very big and highly interactive. SCN5A, CAV3, ALG10B, AKAP9 and many more were mainly found in these cases and were regulated by many transcription factors such as MYOG C2C1 and CBX3 HCT11. Micro RNA, "hsa-miR-133a-3p" was found to be prevalent in the targeted genes. Conclusions: Molecular and computational approaches are a step forward toward exploration of these sad demises. It is so far a new arena but seems promising to dig out the genetic cause of SIDS in the years to come.

A brainstem peptide system activated at birth protects postnatal breathing

Among numerous challenges encountered at the beginning of extrauterine life, the most celebrated is the first breath that initiates a life-sustaining motor activity¹. The neural systems that regulate breathing are fragile early in development, and it is not clear how they adjust to support breathing at birth. Here we identify a neuropeptide system that becomes activated immediately after birth and supports breathing. Mice that lack PACAP selectively in neurons of the retrotrapezoid nucleus (RTN) displayed increased apnoeas and blunted CO₂-stimulated breathing; re-expression of PACAP in RTN neurons corrected these breathing deficits. Deletion of the PACAP receptor PAC1 from the pre-Bötzinger complex-an RTN target region responsible for generating the respiratory rhythm-phenocopied the breathing deficits observed after RTN deletion of PACAP, and suppressed PACAP-evoked respiratory stimulation in the pre-Bötzinger complex. Notably, a postnatal burst of PACAP expression occurred in RTN neurons precisely at the time of birth, coinciding with exposure to the external environment. Neonatal mice with deletion of PACAP in RTN neurons displayed increased apnoeas that were further exacerbated by changes in ambient temperature. Our findings demonstrate that well-timed PACAP expression by RTN neurons provides an important supplementary respiratory drive immediately after birth and reveal key molecular components of a peptidergic neural circuit that supports breathing at a particularly vulnerable period in life.

Sudden Unexplained Death in Childhood: A Neuropathology Review

Sudden Unexplained Death in Childhood (SUDC) is the unexpected death of a child over age 12 months that remains unexplained after a thorough case investigation, including review of the child's medical history, circumstances of death, a complete autopsy and ancillary testing (1). First defined in 2005, SUDC cases are more often male, with death occurring during a sleep period, being found prone, peak winter incidence, associated with febrile seizure history in ~28% of cases and mild pathologic changes insufficient to explain the death (1, 2). There has been little progress in understanding the causes of SUDC and no progress in prevention. Despite reductions in sudden unexpected infant death (SUID) and other causes of mortality in childhood, the rate of SUDC has increased during the past two decades (3-5). In Ireland, SUID deaths were cut in half from 1994 to 2008 while SUDC deaths more than doubled (4). Surveillance issues, including lack of standardized certification practices, affect our understanding of the true magnitude of unexplained child deaths. Mechanisms underlying SUDC, like SUID, remain largely speculative. Limited and inconsistent evidence implicates abnormalities in brainstem autonomic and serotonergic nuclei, critical for arousal, cardiorespiratory control, and reflex responses to life-threatening hypoxia or hypercarbia in sleep (6). Abnormalities in medullary serotonergic neurons and receptors, as well as cardiorespiratory brainstem nuclei occur in some SUID cases, but have never been studied in SUDC. Retrospective, small SUDC studies with non-standardized methodologies most often demonstrate minor hippocampal abnormalities, as well as focal cortical dysplasia and dysgenesis of the brainstem and cerebellum. The significance of these findings to SUDC pathogenesis remains unclear with some investigators and forensic pathologists labeling these findings as normal variants, or potential causes of SUDC. The development of preventive strategies will require a greater understanding of underlying mechanisms.

The role of sodium channels in sudden unexpected death in pediatrics

BACKGROUND

Sudden Unexpected Death in Pediatrics (SUDP) is a tragic event, likely caused by the complex interaction of multiple factors. The presence of hippocampal abnormalities in many children with SUDP suggests that epilepsy-related mechanisms may contribute to death, similar to Sudden Unexplained Death in Epilepsy. Because of known associations between the genes SCN1A and SCN5A and sudden death, and shared mechanisms and patterns of expression in genes encoding many voltage-gated sodium channels (VGSCs), we hypothesized that individuals dying from SUDP have pathogenic variants across the entire family of cardiac arrhythmia- and epilepsy-associated VGSC genes.

METHODS

To address this hypothesis, we evaluated whole-exome sequencing data from infants and children with SUDP for variants in VGSC genes, reviewed the literature for all SUDP-associated variants in VGSCs, applied a novel paralog analysis to all variants, and evaluated all variants according to American College of Medical Genetics and Genomics (ACMG) guidelines.

RESULTS

In our cohort of 73 cases of SUDP, we assessed 11 variants as pathogenic in SCN1A, SCN1B, and SCN10A, genes with long-standing disease associations, and in SCN3A, SCN4A, and SCN9A, VGSC gene paralogs with more recent disease associations. From the literature, we identified 82 VGSC variants in SUDP cases. Pathogenic variants clustered at conserved amino acid sites intolerant to variation across the VGSC genes, which is unlikely to occur in the general population (p < .0001). For 54% of variants previously reported in literature, we identified conflicting evidence regarding pathogenicity when applying ACMG criteria and modern population data.

CONCLUSION

We report variants in several VGSC genes in cases with SUDP, involving both arrhythmia- and epilepsy-associated genes. Accurate variant assessment as well as future studies are essential for an improved understanding of the contribution of sodium channel-related variants to SUDP.

Hippocampal abnormalities and seizures: a 16-year single center review of sudden unexpected death in childhood, sudden unexpected death in epilepsy and SIDS

Sudden Unexpected Death in Childhood (SUDC) is the unexplained death of children aged between 1 and 18 years old. Hippocampal abnormalities have previously been described in Sudden Unexpected Death in Epilepsy (SUDEP) and it is possible that SUDC shares similar pathogenic mechanisms with SUDEP. Our aim was to determine the prevalence of hippocampal abnormalities, history of seizures and demographic features in our caseload of SUDC, SUDEP and SIDS cases. A review of post-mortem reports from 2003 to 2018 was carried out to identify cases of SUDC, SUDEP and SIDS. Histological evidence of hippocampal abnormalities, patient demographics (age, gender), sleeping position, and past medical history (history of seizures and illness 72 hours prior to death) were recorded. Statistical analysis was performed to compare the three groups. 48 SUDC, 18 SUDEP and 358 SIDS cases were identified. Hippocampal abnormalities associated with temporal lobe epilepsy were found in 44.4% of SUDC cases. 5/15 SUDC cases with a history of seizures demonstrated hippocampal abnormalities. SUDC cases were also more likely to be found prone compared to SIDS cases. In comparison with SIDS, both SUDC and SUDEP cases were more likely to demonstrate hippocampal abnormalities (SUDC: (OR = 9.4, 95% CI: 3.1-29.1, p < 0.001; SUDEP: OR = 35.4, 95% CI: 8.3-151.5, p < 0.001). We found a potential link between hippocampal abnormalities and epileptic seizures in SUDC. A concerted effort should be directed towards consistent sampling and standardized description of the hippocampus and clinical correlation with a history of seizures/epilepsy in postmortem reports.

Prenatal intermittent hypoxia sensitizes the laryngeal chemoreflex, blocks serotoninergic shortening of the reflex, and reduces 5-HT3 receptor binding in the NTS in anesthetized rat pups

We tested the hypothesis that exposure to intermittent hypoxia (IH) during pregnancy would prolong the laryngeal chemoreflex (LCR) and diminish the capacity of serotonin (5-hydroxytryptamine; 5-HT) to terminate the LCR. Prenatal exposure to IH was associated with significant prolongation of the LCR in younger, anesthetized, postnatal day (P) rat pups age P8 to P16 compared to control, room air (RA)-exposed rat pups of the same age. Serotonin microinjected into the NTS shortened the LCR in rat pups exposed to RA during gestation, but 5-HT failed to shorten the LCR in rat pups exposed to prenatal IH. Given these observations, we tested the hypothesis that prenatal hypoxia would decrease binding to 5-HT3 receptors in the nucleus of the solitary tract (NTS) where 5-HT acts to shorten the LCR. Serotonin 3 receptor binding was reduced in younger rat pups exposed to IH compared to control, RA-exposed rat pups in the age range P8 to P12. Serotonin 3 receptor binding was similar in older animals (P18-P24) regardless of gas exposure during gestation. The failure of the 5-HT injected into the NTS to shorten the LCR was correlated with a developmental decrease in 5-HT3 receptor binding in the NTS associated with exposure to prenatal IH. In summary, prenatal IH sensitized reflex apnea and blunted processes that terminate reflex apneas in neonatal rat pups, processes that are essential to prevent death following apneas such as those seen in babies who died of SIDS.

A standardized postmortem protocol to assess the real burden of sudden infant death syndrome

Sudden unexpected infant death (SUID) is a major cause of death in infants < 1 year of age. Sudden infant death syndrome (SIDS) is a SUID still unexplained after post-mortem examination. In 2014, a protocol of post-mortem investigation was introduced to assess both the prevalence and the etiopathogenesis of SUID. Our aim was to compare SUID data before and after the application of a standardized autopsy protocol of investigation. In the time interval 2004-2018, SUID cases occurring in the Veneto Region, North-East Italy, were referred to our Core Lab. Since 2014, a complete autopsy was performed, including gross and histological study with toxicologic and molecular analysis carried out at the referral center. A total of 36 SUIDs (22 M, mean age 95.5 ± 80 days), 17 before (group A) and 19 after (group B) 2014, were collected. In group A, only 1 (6%) resulted as explained SUID, due to lymphocytic myocarditis and 16 (94%) were SIDS. In group B, 8 were SIDS (42%) and 11 (58%) explained SUID cases (p < 0.01), consisting of interstitial pneumonia and bronchiolitis in 9 and lymphocytic myocarditis in 2 cases. Molecular analysis was positive for viruses in 8 of them (73%). In conclusion, since the application of a standardized protocol of post-mortem investigation, inflammatory, mostly infective, cardio-pulmonary diseases have been identified as the most common cause of SUID, with SIDS falling from 94 to 42% of SUID. Efforts must be made to implement a uniform autopsy protocol to provide reliable epidemiological data on SIDS.

Distinct Populations of Sudden Unexpected Infant Death Based on Age

OBJECTIVES

In most recent studies, authors combine all cases of sudden infant death syndrome, other deaths from ill-defined or unknown causes, and accidental suffocation and strangulation in bed as a single population to analyze sudden unexpected infant death (SUID). Our aim with this study is to determine if there are statistically different subcategories of SUID that are based on the age of death of an infant.

METHODS

In this retrospective, cross-sectional analysis, we analyzed the Centers for Disease Control and Prevention Birth Cohort Linked Birth/Infant Death Data Set (2003-2013: 41 125 233 births and 37 624 SUIDs). Logistic regression models were developed to identify subpopulations of SUID cases by age of death, and we subsequently analyzed the effects of a set of covariates on each group.

RESULTS

Two groups were identified: sudden unexpected early neonatal deaths (SUENDs; days 0-6) and postperinatal SUIDs (days 7-364). These groups significantly differed in the distributions of assigned International Classification of Diseases, 10th Revision code, live birth order, marital status, age of mother, birth weight, and gestational length compared to postperinatal SUIDs (days 7-364). Maternal smoking during pregnancy was not a significant risk factor for deaths that occurred in the first 48 hours.

CONCLUSIONS

SUEND should be considered as a discrete entity from postperinatal SUID in future studies. These data could help improve the epidemiological understanding of SUEND and SUID and provide clues to a mechanistic understanding underlying the causes of death.

Impaired CO2-Induced Arousal in SIDS and SUDEP

Premature, sudden death is devastating. Certain patient populations are at greater risk to succumb to sudden death. For instance, infants under 1year of age are at risk for sudden infant death syndrome (SIDS), and patients with epilepsy are at risk for sudden unexpected death in epilepsy (SUDEP). Deaths are attributed to these syndromic entities in these select populations when other diagnoses have been excluded. There are a number of similarities between these syndromes, and the commonalities suggest that the two syndromes may share certain etiological features. One such feature may be deficiency of arousal to CO₂. Under normal conditions, CO₂ is a potent arousal stimulus. Circumstances surrounding SIDS and SUDEP deaths often facilitate CO₂ elevation, and faulty CO₂ arousal mechanisms could, at least in part, contribute to death.

Peri-mortem evaluation of infants who die without a diagnosis: focus on advances in genomic technology

Infants who die within the first weeks to months of life may have genetic disorders, though many die without a confirmed diagnosis. Non-genetic conditions may also be responsible for unexplained infant deaths, and the diagnosis may be reliant upon studies performed in the peri-mortem period. Neonatologists, obstetricians, or pediatricians caring for these children and their families may be unsure of which investigations can and should be performed in the setting of a newborn or infant who is dying or has died. Recent advances in genomic sequencing technology may provide additional diagnostic options, though the interpretation of genetic variants discovered by this technique may be contingent upon clinical phenotype information that is obtained peri-mortem or upon autopsy. We have reviewed the current literature concerning the evaluation of an unexplained neonatal or infantile demise and synthesized a diagnostic approach, with a focus on the contribution of new and emerging genomic technologies.

Sudden Infant Death Syndrome: A Review

Sudden infant death syndrome (SIDS) is the sudden unexpected death of an apparently healthy infant younger than age 12 months whose cause of death remains unknown despite a thorough death scene investigation, a review of the clinical history, and an autopsy. Despite the huge achievement of the Back to Sleep program, SIDS remains one of the leading causes of infant death in the United States. In recent years, the SIDS rate has remained stationary despite major public health efforts aimed at high-risk groups to improve sleep environment and strategies. This review focuses on SIDS epidemiology, pathogenesis and risk factors, the American Academy of Pediatrics recommendations on safe infant sleeping environment, and the US Centers for Disease Control and Prevention's multistate registry to improve knowledge on SIDS, evaluate trends, and analyze circumstances and events surrounding SIDS cases. [Pediatr Ann. 2018;47(3):e118-e123.].

Sudden infant death syndrome and inherited cardiac conditions

Sudden infant death syndrome (SIDS) is the leading cause of post-neonatal infant mortality in developed countries, characterized by the death of infants for no obvious reason and without prior warning. The complex interaction of multiple factors in the pathogenesis of SIDS is illustrated by the 'triple risk hypothesis', which proposed that SIDS results from a convergence of three overlapping risk factors: a critical developmental period, an exogenous stressor, and underlying genetic and/or nongenetic vulnerability in the infant. Rare variants in genes associated with inherited arrhythmia syndromes and cardiomyopathies have been proposed as the substrate for an infant's critical vulnerability in a small subset of SIDS cases. Given the potential risk of inherited cardiac disease, current guidelines recommend post-mortem genetic testing (molecular autopsy) and cardiological investigation of the surviving family, complemented by targeted genetic testing if appropriate. In this Review, we highlight the latest developments in understanding the spectrum and prevalence of cardiac-mediated SIDS, and discuss the clinical implications of SIDS in the surviving family and the general population.

Update on congenital heart disease and sudden infant/perinatal death: from history to future trends

During the 20th century, expert pathologists contributed an in-depth characterisation of the anatomical pathology and associated pathophysiology of congenital heart disease (CHD). Starting in the 1970s, the reported CHD birth prevalence has been increasing, owing to advances in diagnostic methods. Over the years, surgical treatments have been associated with an enormous reduction of CHD mortality. Advances also have been made in understanding the developmental biology and molecular pathogenesis of CHD. In developed countries, sudden infant death syndrome (SIDS) is the most frequent form of death during the first year of life, with a death rate of 0.42 every 1000 births. Unexpected stillbirth has a six- to eightfold greater incidence than that of SIDS and remains unexplained in 40–80% of cases even after autopsy. Specific environmental risk factors, such as maternal smoking, air and water pollution, food contamination, pesticides, etc, can interact with the genetic constitution in complex ways, which may lead to polymorphisms and/or mutations of specific genes, such as polymorphisms in the serotonin transporter gene 5-HTT, the regulator of the synaptic serotonin concentration. Current directions of research in this area are reviewed.

Hippocampal Formation Maldevelopment and Sudden Unexpected Death across the Pediatric Age Spectrum

Sudden infant death syndrome (SIDS) and sudden unexplained death in childhood (SUDC) are defined as sudden death in a child remaining unexplained despite autopsy and death scene investigation. They are distinguished from each other by age criteria, i.e. with SIDS under 1 year and SUDC over 1 year. Our separate studies of SIDS and SUDC provide evidence of shared hippocampal abnormalities, specifically focal dentate bilamination, a lesion classically associated with temporal lobe epilepsy, across the 2 groups. In this study, we characterized the clinicopathologic features in a retrospective case series of 32 children with sudden death and hippocampal formation (HF) maldevelopment. The greatest frequency of deaths was between 3 weeks and 3 years (81%, 26/32). Dentate anomalies were found across the pediatric age spectrum, supporting a common vulnerability that defies the 1-year age cutoff between SIDS and SUDC. Twelve cases (38%) had seizures, including 7 only with febrile seizures. Subicular anomalies were found in cases over 1 year of age and were associated with increased risk of febrile seizures. Sudden death associated with HF maldevelopment reflects a complex interaction of intrinsic and extrinsic factors that lead to death at different pediatric ages, and may be analogous to sudden unexplained death in epilepsy.

Defining Sudden Infant Death and Sudden Intrauterine Unexpected Death Syndromes with Regard to Anatomo-Pathological Examination

Crib death, or sudden infant death syndrome (SIDS), is the most frequent form of death in the first year of life, striking one baby in every 1,700-2,000. Yet, despite advances in maternal-infant care, sudden intrauterine unexplained/unexpected death syndrome (SIUDS) has a sixfold to eightfold greater incidence than that of SIDS. Frequent congenital abnormalities, likely morphological substrates for SIDS-SIUDS, were detected, mainly represented by alterations of the cardiac conduction system, such as accessory pathways and abnormal resorptive degeneration, and hypoplasia/agenesis of the vital brainstem structures. On the basis of these considerations, the new common definition of the SIDS-SIUDS complex is "The sudden death of a fetus after the 25th gestational week or infant under one year of age which is unexpected by history and remains unexplained after a thorough case investigation, including examination of the death scene, performance of a general autopsy and examination of the fetal adnexa". Therefore, given that the general autopsy does not disclose any cause of death, a more in-depth histopathological analysis of the cardiac conduction system and autonomic nervous system by specialized pathologists is necessary.