Sudden Unexpected Infant Deaths: 2015-2020

OBJECTIVE

Although the US infant mortality rate reached a record low in 2020, the sudden infant death syndrome (SIDS) rate increased from 2019. To understand if the increase was related to changing death certification practices or the coronavirus disease 2019 (COVID-19) pandemic, we examined sudden unexpected infant death (SUID) rates as a group, by cause, and by race and ethnicity.

METHODS

We estimated SUID rates during 2015 to 2020 using US period-linked birth and death data. SUID included SIDS, unknown cause, and accidental suffocation and strangulation in bed. We examined changes in rates from 2019 to 2020 and assessed linear trends during prepandemic (2015-2019) using weighted least squares regression. We also assessed race and ethnicity trends and quantified COVID-19-related SUID.

RESULTS

Although the SIDS rate increased significantly from 2019 to 2020 (P < .001), the overall SUID rate did not (P = .24). The increased SIDS rate followed a declining linear trend in SIDS during 2015 to 2019 (P < .001). Other SUID causes did not change significantly. Our race and ethnicity analysis showed SUID rates increased significantly for non-Hispanic Black infants from 2019 to 2020, widening the disparities between these two groups during 2017 to 2019. In 2020, <10 of the 3328 SUID had a COVID-19 code.

CONCLUSIONS

Diagnositic shifting likely explained the increased SIDS rate in 2020. Why the SUID rate increased for non-Hispanic Black infants is unknown, but warrants continued monitoring. Interventions are needed to address persistent racial and ethnic disparities in SUID.

Half Century Since SIDS: A Reappraisal of Terminology

After a sudden infant death, parents and caregivers need accurate and open communication about why their infant died. Communicating tragic news about a child's death to families and caregivers is difficult. Shared and consistent terminology is essential for pediatricians, other physicians, and nonphysician clinicians to improve communication with families and among themselves. When families do not have complete information about why their child died, pediatricians will not be able to support them through the process and make appropriate referrals for pediatric specialty and mental health care. Families can only speculate about the cause and may blame themselves or others for the infant's death. The terminology used to describe infant deaths that occur suddenly and unexpectedly includes an assortment of terms that vary across and among pediatrician, other physician, or nonphysician clinician disciplines. Having consistent terminology is critical to improve the understanding of the etiology, pathophysiology, and epidemiology of these deaths and communicate with families. A lack of consistent terminology also makes it difficult to reliably monitor trends in mortality and hampers the ability to develop effective interventions. This report describes the history of sudden infant death terminology and summarizes the debate over the terminology and the resulting diagnostic shift of these deaths. This information is to assist pediatricians, other physicians, and nonphysician clinicians in caring for families during this difficult time. The importance of consistent terminology is outlined, followed by a summary of progress toward consensus. Recommendations for pediatricians, other physicians, and nonphysician clinicians are proposed.

Pathologizing the Unknown: A Sociological Explanation for the (Mis-)Use of Sudden Infant Death Syndrome as a Diagnosis

Sudden infant death syndrome (SIDS) is a diagnosis given to infants who die suddenly and unexpectedly before the age of one. After decades of research into SIDS, little has been conclusively determined regarding the etiology of this phenomenon. While SIDS deaths are in reality undetermined deaths, there is resistance to abandon SIDS and synonymous terminology. This paper identifies the social functions that a diagnosis of SIDS provides both to the families of the deceased, as well as the physicians who treat them. It is suggested that these social functions help to explain why, despite being inaccurate and misleading, SIDS is still widely used today. It is argued, however, that the forensic pathology and medical community as a whole should lead a systematic shift away from the use of SIDS as a diagnosis. Adopting more medically-appropriate terminology would better serve the goals of the medical profession and the families they serve.

Urban-Rural Infant Mortality Disparities by Race and Ethnicity and Cause of Death

INTRODUCTION

Infant mortality rates are higher in nonmetropolitan areas versus large metropolitan areas. Variation by race/ethnicity and cause of death has not been assessed. Urban-rural infant mortality rate differences were quantified by race/ethnicity and cause of death.

METHODS

National Vital Statistics System linked birth/infant death data (2014-2016) were analyzed in 2019 by 3 urban-rural county classifications: large metropolitan, medium/small metropolitan, and nonmetropolitan. Excess infant mortality rates (rate differences) by urban-rural classification were calculated relative to large metropolitan areas overall and for each racial/ethnic group. The number of excess deaths, population attributable fraction, and proportion of excess deaths attributable to underlying causes of death was calculated.

RESULTS

Nonmetropolitan areas had the highest excess infant mortality rate overall. Excess infant mortality rates were substantially lower for Hispanic infants than other races/ethnicities. Overall, 7.4% of infant deaths would be prevented if all areas had the infant mortality rate of large metropolitan areas. With more than half of births occurring outside of large metropolitan areas, the population attributable fraction was highest for American Indian/Alaska Natives (20.3%) and whites, non-Hispanic (14.3%). Excess infant mortality rates in both nonmetropolitan and medium/small metropolitan areas were primarily attributable to sudden unexpected infant deaths (42.3% and 31.9%) and congenital anomalies (30.1% and 26.8%). This pattern was consistent for all racial/ethnic groups except black, non-Hispanic infants, for whom preterm-related and sudden unexpected infant deaths accounted for the largest share of excess infant mortality rates.

CONCLUSIONS

Infant mortality increases with rurality, and excess infant mortality rates are predominantly attributable to sudden unexpected infant deaths and congenital anomalies, with differences by race/ethnicity regarding magnitude and cause of death.

Racial differences within subsets of Sudden Unexpected Infant Death (SUID) with an emphasis on asphyxia

OBJECTIVE

Sudden Unexpected Infant Deaths (SUID) is defined as a combination of Sudden Infant Death Syndrome (SIDS), Unknown Cause of Death (UCD) and Accidental Suffocation and Strangulation in Bed (ASSB). Overall rates from 2000 to 2015 have been trending down. Racial differences in occurrence are seen.

STUDY DESIGN AND SETTING

Using the CDC Wonder Database, the total rates of SUID and its subsets were examined.

RESULTS

Non-Caucasian infant death rates for the total SUID group, and the SIDS component, are trending downward significantly faster than for Caucasians. UCD trends in rates show an apparent small, non-significant, decline for non-Caucasians, and are unchanged for Caucasians. ASSB rates are trending upward slightly more rapidly (not significantly) for non-Caucasians than Caucasians.

CONCLUSION

The trend showing ASSB trending upward more in non-Caucasians than Caucasians may suggest: 1) A racial difference that certifiers are more willing to certify SIDS than ASSB in Caucasians, and/or 2) Certifiers are biased towards certifying more ASSB than SIDS in non-Caucasians, and/or 3) Asphyxia risks may be increasing more in non-Caucasian SUIDs. Option #1 would require educational efforts to recognize the asphyxia risks in Caucasians. Option #2 would require documentation of racial bias in infant death certification followed by efforts to reduce the bias. Option #3 would require focused targeting of non-Caucasian populations to reduce asphyxia risks. Potentially all three scenarios could co-exist.

Birth Order and Injury-Related Infant Mortality in the U.S

INTRODUCTION

The purpose of this study was to evaluate the risk of death during the first year of life due to injury, such as unintentional injury and homicide, by birth order in the U.S.

METHODS

Using national birth cohort-linked birth-infant death data (births, 2000-2010; deaths, 2000-2011), risks of infant mortality due to injury in second-, third-, fourth-, and fifth or later-born singleton infants were compared with first-born singleton infants. Risk ratios were estimated using log-binomial models adjusted for maternal age, marital status, race/ethnicity, and education. The statistical analyses were conducted in 2016.

RESULTS

Approximately 40%, 32%, 16%, 7%, and 4% of singleton live births were first, second, third, fourth, and fifth or later born, respectively. From 2000 to 2011, a total of 15,866 infants died as a result of injury (approximately 1,442 deaths per year). Compared with first-born infants (2.9 deaths per 10,000 live births), second or later-born infants were at increased risk of infant mortality due to injury (second, 3.6 deaths; third, 4.2 deaths; fourth, 4.8 deaths; fifth or later, 6.4 deaths). The corresponding adjusted risk ratios were as follows: second, 1.84 (95% CI=1.76, 1.91); third, 2.42 (95% CI=2.30, 2.54); fourth, 2.96 (95% CI=2.77, 3.16); and fifth or later, 4.26 (95% CI=3.96, 4.57).

CONCLUSIONS

Singleton infants born second or later were at increased risk of mortality due to injury during their first year of life in the U.S. This study's findings highlight the importance of investigating underlying mechanisms behind this increased risk.

Variations in Cause-of-Death Determination for Sudden Unexpected Infant Deaths

OBJECTIVES

To quantify and describe variation in cause-of-death certification of sudden unexpected infant deaths (SUIDs) among US medical examiners and coroners.

METHODS

From January to November 2014, we conducted a nationally representative survey of US medical examiners and coroners who certify infant deaths. Two-stage unequal probability sampling with replacement was used. Medical examiners and coroners were asked to classify SUIDs based on hypothetical scenarios and to describe the evidence considered and investigative procedures used for cause-of-death determination. Frequencies and weighted percentages were calculated.

RESULTS

Of the 801 surveys mailed, 60% were returned, and 377 were deemed eligible and complete. Medical examiners and coroners classification of infant deaths varied by scenario. For 3 scenarios portraying potential airway obstruction and negative autopsy findings, 61% to 69% classified the death as suffocation/asphyxia. In the last scenario, which portrayed a healthy infant in a safe sleep environment with negative autopsy findings, medical examiners and coroners classified the death as sudden infant death syndrome (38%) and SUID (30%). Reliance on investigative procedures to determine cause varied, but 94% indicated using death scene investigations, 88% full autopsy, 85% toxicology analyses, and 82% medical history review.

CONCLUSIONS

US medical examiners and coroners apply variable practices to classify and investigate SUID, and thus, they certify the same deaths differently. This variability influences surveillance and research, impacts true understanding of infant mortality causes, and inhibits our ability to accurately monitor and ultimately prevent future deaths. Findings may inform future strategies for promoting standardized practices for SUID classification.

Ten Percent of SIDS Cases are Murder - or are They?

Sudden infant death syndrome (SIDS) has been used as a cause of death for over four decades. It has allowed deaths of infants to be registered as natural. Within this group of deaths, a certain number have been recognized to be homicides from inflicted smothering rather than being natural or accidental deaths. Research has been conducted using confidential inquires to determine how frequent homicide is in cases called SIDS. This paper traces the history of quoted rates of homicide. Early work suggested the figure was between 2-10% of all SIDS cases, though other workers have suggested figures as high as 20-40%. With the fall in the rate of infant deaths following the "Back to Sleep" campaigns, these figures have been reevaluated. If the higher figures were correct that 20-40% of SIDS were homicides, the fall in infant deaths would be expected to be less than it has been. Current data suggests a much lower figure than 10% of current cases, with much lower overall rates of infant deaths. As well as 10% of SIDS cases having been stated to be homicides, a related question is whether multiple deaths classified as SIDS are really homicides. The paper discusses the maxim that one death is a tragedy, two is suspicious, and three deaths indicate homicide. The paper also looks at court cases and the approach that has been made in prosecutions of sudden unexpected death in infancy as multiple murder.

Plurality of Birth and Infant Mortality Due to External Causes in the United States, 2000-2010

Risk of death during the first year of life due to external causes, such as unintentional injury and homicide, may be higher among twins and higher-order multiples than among singletons in the United States. We used national birth cohort linked birth-infant death data (2000-2010) to evaluate the risk of infant mortality due to external causes in multiples versus singletons in the United States. Risk of death from external causes during the study period was 3.6 per 10,000 live births in singletons and 5.1 per 10,000 live births in multiples. Using log-binomial regression, the corresponding unadjusted risk ratio was 1.40 (95% confidence interval (CI): 1.30, 1.50). After adjustment for maternal age, marital status, race/ethnicity, and education, the risk ratio was 1.68 (95% CI: 1.56, 1.81). Infant deaths due to external causes were most likely to occur between 2 and 7 months of age. Applying inverse probability weighting and assuming a hypothetical intervention where no infants were low birth weight, the adjusted controlled direct effect of plurality on infant mortality due to external causes was 1.64 (95% CI: 1.39, 1.97). Twins and higher-order multiples were at greater risk of infant mortality due to external causes, particularly between 2 and 7 months of age, and this risk appeared to be mediated largely by factors other than low-birth-weight status.

Prepregnancy Body Mass Index and Infant Mortality in 38 U.S. States, 2012-2013

OBJECTIVE

To estimate whether prepregnancy body mass index (BMI) is related to infant mortality and whether adherence to weight gain recommendations mitigates the relationship between BMI and infant mortality.

METHODS

This was a cohort study using 2012-2013 U.S. national linked birth certificate and infant death files for 38 states and the District of Columbia with the BMI measure, including 6,419,836 singleton births and 36,691 infant deaths (infant mortality rate 5.72/1,000). Prenatal weight gain in three categories was based on adherence to Institute of Medicine recommendations. The outcome measure was infant deaths in the first year of life subdivided into two time periods: neonatal (less than 28 days) and postneonatal (28 days to 1 year).

RESULTS

With normal prepregnancy weight as a reference, after adjustment, the odds ratio (OR) for an infant death rose from 1.32 (95% confidence interval [CI] 1.27-1.37) for mothers in the obese I category to 1.73 (95% CI 1.64-1.83) for obese III. Higher BMI was related to higher rates of both neonatal and postneonatal mortality. The adjusted OR for the risk of an infant death among singleton, term, vertex births for those gaining less than the recommended weight was 1.07 (95% CI 1.01-1.12) and 1.04 (95% CI 0.99-1.09) for those gaining more than recommended.

CONCLUSION

Even after controlling for multiple risks, prepregnancy BMI was strongly related to infant mortality. Efforts to lower the infant mortality rate may benefit from a focus on reducing obesity among women of reproductive age.

Sudden Unexpected Death in Fetal Life Through Early Childhood

In March 2015, the Eunice Kennedy Shriver National Institute of Child Health and Human Development held a workshop entitled "Sudden Unexpected Death in Fetal Life Through Early Childhood: New Opportunities." Its objective was to advance efforts to understand and ultimately prevent sudden deaths in early life, by considering their pathogenesis as a potential continuum with some commonalities in biological origins or pathways. A second objective of this meeting was to highlight current issues surrounding the classification of sudden infant death syndrome (SIDS), and the implications of variations in the use of the term "SIDS" in forensic practice, and pediatric care and research. The proceedings reflected the most current knowledge and understanding of the origins and biology of vulnerability to sudden unexpected death, and its environmental triggers. Participants were encouraged to consider the application of new technologies and "omics" approaches to accelerate research. The major advances in delineating the intrinsic vulnerabilities to sudden death in early life have come from epidemiologic, neural, cardiac, metabolic, genetic, and physiologic research, with some commonalities among cases of unexplained stillbirth, SIDS, and sudden unexplained death in childhood observed. It was emphasized that investigations of sudden unexpected death are inconsistent, varying by jurisdiction, as are the education, certification practices, and experience of death certifiers. In addition, there is no practical consensus on the use of "SIDS" as a determination in cause of death. Major clinical, forensic, and scientific areas are identified for future research.

Investigation of Sudden Unexpected Infant Deaths

The investigation of infant death is complex and requires synergy between multiple agencies including law enforcement, Child Protective Services, medicolegal death investigators, and forensic pathologists. Prior to the forensic pediatric autopsy, the death investigator must identify the types of death scenes involved (e.g., hospital, residence, daycare) and document the details of the scene. Interviews must be conducted with the caregivers and other family members (including doll reenactments), law enforcement, pediatricians, and emergency medical personnel. The forensic pathologist must be able to conduct a comprehensive pediatric forensic autopsy and be aware of the specific challenges related to cases of sudden unexpected infant deaths. This article provides an overview of infant death investigation, discussing the roles and responsibilities of the medicolegal death investigator and the forensic pathologist.

Inference in Forensic Pathology

Forensic pathologists make inferences about cause and manner of death. Those inferences have come under increasing scrutiny by the courts, by social critics of our findings, and by society at large. Much of this criticism is due to our inability to explain our inferential process. Forensic pathologists should be able to cogently explain the reasoning behind their findings, and express it in terms useful to stakeholders. This requires that we have a basic understanding of different kinds of inference and the scientific method, how they are used and their limitations. Medical diagnosis is not a simple matter of application of cookbook-style inferential laws, but involves a combination of deduction, induction, abduction, dialectic, and informal inference. There are significant differences between the way physicians make inferences compared to how they justify them. A discussion of different kinds of inference, inferential fallacies, evaluation of evidence, causation, and the scientific method is provided, with illustrations from the practice of forensic pathology.

Critical Appraisal of Scientific Literature

Despite the relatively small size of our profession, there is abundant scientific literature within the field of forensic pathology. The written word does not imply truth, however, and it is vitally important that the forensic pathologist approach the literature with a critical eye and understand how to evaluate a paper for oneself and come to a conclusion regarding its validity and the level of evidence it provides. The purpose of this paper is to provide a basic outline of the concepts important to critically reviewing a scientific paper; not so much as a peer reviewer, but rather as a practicing medical consumer of information. It will outline the key steps in approaching and reading a scientific study: identifying the type of study the paper represents, describing the process of critically reading the paper, assessing its scientific quality, describing various types of errors and where to look for them within the paper, and assessing the level of evidence provided in the study.

Infant Heart Dissection in a Forensic Context: Babies are Not Just Small Adults

Medical examiners who investigate infant deaths are required to consider a large number of natural and non-natural causes due to the broad differential diagnosis of unexpected infant death. Among the myriad of causes are those related to disorders in structure and function of the cardiovascular system. Adult hearts are routinely and efficiently evaluated by medical examiners because of the large anatomic structures and limited spectrum of commonly encountered diseases. Infant deaths are comparatively rare. Although infant hearts may be evaluated with similar efficiency, the pathologist must first have a detailed knowledge of developmental cardiovascular anatomy and of the subtleties of a broad spectrum of infantile cardiovascular pathology. Furthermore, the pathologist must be aware of additional details to be observed and documented in infant cardiac studies, and of the dissection techniques that facilitate acquisition of that data. Rote dissection of an infant heart as if it were an adult heart may lead to overlooked malformations and diseases that may have been the underlying cause of death. This brief review paper covers the fundamentals of pediatric cardiovascular anatomy and dissection techniques as they apply to the practice of pediatric forensic pathology.