The male excess in sudden infant deaths

National SIDS Trends in the United States From 2000 to 2019: A Population-Based Study on 80 Million Live Births

Sudden infant death syndrome (SIDS) is the most common cause of death for infants between 1 month and 1 year of age in the United States. The objective was to examine recent trends in SIDS in the United States, over time and by sex and race. A population-based cross-sectional study was conducted on 80 710 348 live births using data from the Center for Disease Control and Prevention's (CDC) "Birth Data" and "Mortality Multiple Cause" files from 2000 to 2019. Logistic regression examined the effects of sex and race on the risk of SIDS and examined temporal changes in risk across sex and race over the study period. Incidence of SIDS decreased from 6.3 to 3.4/10 000 births from 2000 to 2019, with an overall incidence of 4.9/10 000 births (95% confidence interval [CI] = 4.4-5.3). Male infants were at the greatest risk of SIDS as were black and American Indian infants. Although SIDS incidence decreased by sex and race over time, the decline was smaller among Hispanic and American Indian infants.

Prenatal smoking and drinking are associated with altered newborn autonomic functions

BACKGROUND

Prenatal smoking and drinking are associated with sudden infant death syndrome and neurodevelopmental disorders. Infants with these outcomes also have altered autonomic nervous system (ANS) regulation. We examined the effects of prenatal smoking and drinking on newborn ANS function.

METHODS

Pregnant women were enrolled in Northern Plains, USA (NP) and Cape Town (CT), South Africa. Daily drinking and weekly smoking data were collected prenatally. Physiological measures were obtained during sleep 12-96 h post-delivery.

RESULTS

In all, 2913 infants from NP and 4072 from CT were included. In active sleep, newborns of mothers who smoked throughout pregnancy, compared to non-smokers, had higher breathing rates (2.2 breaths/min; 95% CI: 0.95, 3.49). Quit-early smoking was associated with reductions in beat-to-beat heart rate variability (HRV) in active (-0.08 s) and quiet sleep (-0.11 s) in CT. In girls, moderate-high continuous smoking was associated with increased systolic (3.0 mmHg, CI: 0.70, 5.24) and diastolic blood pressure (2.9 mmHg, CI: 0.72, 5.02). In quiet sleep, low-continuous drinking was associated with slower heart rate (-4.5 beat/min). In boys, low-continuous drinking was associated with a reduced ratio of low-to-high frequency HRV (-0.11, CI: -0.21, -0.02).

CONCLUSIONS

These findings highlight potential ANS pathways through which prenatal drinking and smoking may contribute to neurodevelopment outcomes.

IMPACT

In this prospective cohort study of 6985 mother-infant dyads prenatal drinking and smoking were associated with multiple ANS parameters. Smoking was associated with increased neonatal breathing rates among all infants, and heart rate variability (HRV) and blood pressure (BP) among girls. Drinking was associated with reductions in HR and BP among all newborns, and reductions in the ratio of low to-high frequency HRV among boys. These findings suggest that prenatal smoking and drinking alter newborn ANS which may presage future neurodevelopmental disorders.

Cardiorespiratory alterations in a newborn ovine model of systemic viral inflammation

BACKGROUND

Respiratory viruses can be responsible for severe apneas and bradycardias in newborn infants. The link between systemic inflammation with viral sepsis and cardiorespiratory alterations remains poorly understood. We aimed to characterize these alterations by setting up a full-term newborn lamb model of systemic inflammation using polyinosinic:polycytidylic acid (Poly I:C).

METHODS

Two 6-h polysomnographic recordings were carried out in eight lambs on two consecutive days, first after an IV saline injection, then after an IV injection of 300 μg/kg Poly I:C.

RESULTS

Poly I:C injection decreased locomotor activity and increased NREM sleep. It also led to a biphasic increase in rectal temperature and heart rate. The latter was associated with an overall decrease in heart-rate variability, with no change in respiratory-rate variability. Lastly, brainstem inflammation was found in the areas of the cardiorespiratory control centers 6 h after Poly I:C injection.

CONCLUSIONS

The alterations in heart-rate variability induced by Poly I:C injection may be, at least partly, of central origin. Meanwhile, the absence of alterations in respiratory-rate variability is intriguing and noteworthy. Although further studies are obviously needed, this might be a way to differentiate bacterial from viral sepsis in the neonatal period.

IMPACT

Provides unique observations on the cardiorespiratory consequences of injecting Poly I:C in a full-term newborn lamb to mimic a systemic inflammation secondary to a viral sepsis. Poly I:C injection led to a biphasic increase in rectal temperature and heart rate associated with an overall decrease in heart-rate variability, with no change in respiratory-rate variability. Brainstem inflammation was found in the areas of the cardiorespiratory control centers.

Vaccines and sudden infant death: An analysis of the VAERS database 1990-2019 and review of the medical literature

Although there is considerable evidence that a subset of infants has an increased risk of sudden death after receiving vaccines, health authorities eliminated "prophylactic vaccination" as an official cause of death, so medical examiners are compelled to misclassify and conceal vaccine-related fatalities under alternate cause-of-death classifications. In this paper, the Vaccine Adverse Event Reporting System (VAERS) database was analyzed to ascertain the onset interval of infant deaths post-vaccination. Of 2605 infant deaths reported to VAERS from 1990 through 2019, 58 % clustered within 3 days post-vaccination and 78.3 % occurred within 7 days post-vaccination, confirming that infant deaths tend to occur in temporal proximity to vaccine administration. The excess of deaths during these early post-vaccination periods was statistically significant (p < 0.00001). A review of the medical literature substantiates a link between vaccines and sudden unexplained infant deaths. Several theories regarding the pathogenic mechanism behind these fatal events have been proposed, including the role of inflammatory cytokines as neuromodulators in the infant medulla preceding an abnormal response to the accumulation of carbon dioxide; fatal disorganization of respiratory control induced by adjuvants that cross the blood-brain barrier; and biochemical or synergistic toxicity due to multiple vaccines administered concurrently. While the findings in this paper are not proof of an association between infant vaccines and infant deaths, they are highly suggestive of a causal relationship.

The multiagency approach to Sudden Unexpected Infant Deaths (SUID): eleven years' experience in the Tuscany Region

Background

The Sudden Unexpected Infant Death Syndrome (SUID) is one of the leading causes of mortality in the first year of life. The aim of this work was the retrospective evaluation of the incidence of SUID and the effectiveness of the multiagency approach to this phenomenon in the Tuscany Region.

Methods

Data were obtained from the regional registry of SUID cases in the period 2009–2019. The registry contains both sudden unexpected deaths in the first week of life (Sudden Unexpected Early Neonatal Deaths - SUEND), and those occurring after the first week up to 1 year of age (SUID).

Results

In this timeframe a total of 73 sudden unexpected deaths occurred in our region; 32 were Unexplained (i.e. Sudden Infant Death Syndrome - SIDS), 24 Explained, 10 Undetermined, and 7 SUEND. Autopsies were performed in 91% of cases, and in 95% of these by three groups of selected pathologists according to our protocol.

We found a low incidence of SUID (0.21 ‰), and SIDS deaths accounted for 0.1‰ of live births (48% of cases) with a high prevalence of infants of non-Italian ethnicity (38% of cases). Bereaved families were able to receive psychological support from mental health professionals and have contact with the family association, Seeds for SIDS. Audits were organized when post-mortem examinations were not carried out or carried out incorrectly in procedural terms, and when the diagnosis was particularly uncertain.

Conclusions

This paper first provides data on SUID mortality based on complete post-mortems in an Italian region. According to these findings we can state that our approach is effective both in terms of correctly performed autopsies and support for bereaved families. Future efforts are necessary to further reduce the incidence of SUID especially among non- Italian infants. An improvement action is also recommended for ensuring a more accurate and consistent picture of the circumstances of death.

The final approval of the National Protocol for the management of SUID cases is therefore strongly advocated in order to improve surveillance in this specific field and abolish disparities among the Italian regions.

Colostrum immunoglobulins and oxidative capacity may be affected by infant sex and maternal age and parity

Background/aim

The aims of this study were to determine the levels of the total antioxidant status (TAS), the total oxidant status (TOS), the oxidative stress index (OSI), and the concentration of immunoglobulin A (IgA) and M (IgM) in colostrum, and evaluate relationships between these parameters and maternal age, maternal parity, and infant sex.

Materials and methods

The analysis was performed in serum samples of colostrum which were collected from 90 mothers on the first day of lactation between 10:00 and 12:00 AM.

Results

The measurements established that no significant association existed between the TAS level of colostrum and parity, maternal age, or infant sex. However, mothers 18 to 30 years of age had significantly lower colostrum TOS and OSI levels compared with mothers older than 30 years of age. IgA and IgM values of the colostrum of primiparous mothers were significantly higher than those of multiparous mothers, whereas no correlations existed with the age of the mother. Additionally, significantly higher colostrum IgA and IgM values were observed in female infants fed colostrum compared with male infants.

Conclusion

In conclusion, sex-based hormonal changes in mothers during pregnancy may be associated with the different colostral immunoglobulin levels for male and female infants.

A systematic review exploring the relationship between infection and sudden unexpected death between 2000 and 2016: A forensic perspective

Death due to infectious diseases is a major health concern worldwide. This is of particular concern in developing countries where poor-socio economic status and a lack of healthcare resources contribute to the high burden of disease. In some cases death due to infection can be acute and aggressive, and death may occur without a diagnosis whilst the person is still alive. These deaths may ultimately lead to a medico-legal autopsy being performed. There are various mechanisms by which sudden death due to infection may occur. In addition, there are many risk factors associated with sudden death due to infection, which differ between infants and older individuals. However, it is unclear which pathogens and risk factors are most frequently associated with sudden death due to infection. Therefore a systematic review of articles and case reports published between 1 January 2000 and 30 June 2016 was undertaken in order to (1) explore the relationship between pathogens and their causative role and (2) identify the relationship between predisposing and/or risk factors associated with sudden death due to infection. Major databases were searched and after critical appraisal 143 articles were identified. It was found that respiratory infections and deaths involving bacterial pathogens were most commonly associated with these deaths. In addition the most common risk factors in infants were exposure to tobacco smoke and co-sleeping. In adults the most common risk factors were co-morbid conditions and illnesses. This information aids in a better understanding of these deaths and highlights the need for more research in this field, particularly in developing countries.

Medullary Astrogliosis in Sudden Infant Death Syndrome Varies With Sleeping Environment: Evidence for Different Mechanisms of Death in Alone Versus Co-sleepers?

Sudden infant death syndrome remains the leading cause of death in infants under 1 year, and underlying pathophysiological mechanisms are poorly understood. The current study investigated the hypothesis that co-sleepers die more rapidly from causes such as suffocation from overlaying by comparing levels of reactive astrogliosis in the medulla of infants who died sleeping alone to those who died co-sleeping. The amount of glial fibrillary acidic protein (GFAP) staining in alone sleepers was significantly higher than shared sleepers in 3 specific areas of the medulla, the inferior vestibular nucleus, the medial vestibular nucleus and the cochlear nucleus. Given that glial fibrillary acidic protein elevations follow a delayed time course, this suggests that death in co-sleepers was more rapid, not allowing for reactive gliosis to occur. This provides evidence of pathological differences in mechanisms of death in infants who are classified as having died from sudden infant death syndrome, suggesting potential need for refinement of categorization of these cases.

Fetal sex is associated with maternal stimulated cytokine production, but not serum cytokine levels, in human pregnancy

Some studies suggest that fetal sex plays a role in maternal physiological processes during pregnancy including glycemic control, blood pressure, and cortisol regulation. However, data examining fetal sex-specific differences in maternal immune parameters is lacking. In the current study, serum levels of interleukin(IL)-6, IL-8, and tumor necrosis factor(TNF)-α as well as LPS-stimulated production of IL-6, IL-8, TNF-α, and IL-1β by PBMCs incubated for 24h were assessed in early, mid, and late pregnancy among 80 women (46 with male and 34 with female fetuses). Linear mixed models showed that women carrying females versus males exhibited greater stimulated production of IL-6 at each timepoint (ps⩽0.03), TNF-α in early pregnancy (p=0.04), and IL-1β in mid- and late pregnancy (ps⩽0.05). Despite changes in serum levels of IL-8 (p=0.002) and TNF-α (p<0.0001) across pregnancy, no differences in any serum cytokines were observed in relation to fetal sex (ps>0.85). In conclusion, in pregnant women, those carrying female versus male fetuses exhibited greater stimulated cytokine production across pregnancy. Differential inflammatory responses could affect maternal health and fetal development. Fetal sex should be considered as a factor in studies of maternal inflammation. These findings have relevance both clinically and conceptually. For example, maternal asthma is exacerbated among women carrying female versus male fetuses. In addition, data on associations between fetal sex and maternal immune function among women with health conditions (e.g., preeclampsia) and adverse pregnancy outcomes (e.g., preterm birth) would be informative.

A "Wear and Tear" Hypothesis to Explain Sudden Infant Death Syndrome

Sudden infant death syndrome (SIDS) is the leading cause of death among USA infants under 1 year of age accounting for ~2,700 deaths per year. Although formally SIDS dates back at least 2,000 years and was even mentioned in the Hebrew Bible (Kings 3:19), its etiology remains unexplained prompting the CDC to initiate a sudden unexpected infant death case registry in 2010. Due to their total dependence, the ability of the infant to allostatically regulate stressors and stress responses shaped by genetic and environmental factors is severely constrained. We propose that SIDS is the result of cumulative painful, stressful, or traumatic exposures that begin in utero and tax neonatal regulatory systems incompatible with allostasis. We also identify several putative biochemical mechanisms involved in SIDS. We argue that the important characteristics of SIDS, namely male predominance (60:40), the significantly different SIDS rate among USA Hispanics (80% lower) compared to whites, 50% of cases occurring between 7.6 and 17.6 weeks after birth with only 10% after 24.7 weeks, and seasonal variation with most cases occurring during winter, are all associated with common environmental stressors, such as neonatal circumcision and seasonal illnesses. We predict that neonatal circumcision is associated with hypersensitivity to pain and decreased heart rate variability, which increase the risk for SIDS. We also predict that neonatal male circumcision will account for the SIDS gender bias and that groups that practice high male circumcision rates, such as USA whites, will have higher SIDS rates compared to groups with lower circumcision rates. SIDS rates will also be higher in USA states where Medicaid covers circumcision and lower among people that do not practice neonatal circumcision and/or cannot afford to pay for circumcision. We last predict that winter-born premature infants who are circumcised will be at higher risk of SIDS compared to infants who experienced fewer nociceptive exposures. All these predictions are testable experimentally using animal models or cohort studies in humans. Our hypothesis provides new insights into novel risk factors for SIDS that can reduce its risk by modifying current infant care practices to reduce nociceptive exposures.

Sudden unexpected death in infancy: aetiology, pathophysiology, epidemiology and prevention in 2015

Despite the fall in numbers of unexpected infant deaths that followed the 'Back to Sleep' campaigns in the early 1990 s in the UK and many other countries, such deaths remain one of the largest single groups of deaths in the postneonatal period in many Western countries. Changes in the ways in which unexpected infant deaths are categorised by pathologists and coroners, and increasing reluctance to use the term 'sudden infant death syndrome', make assessment of nationally and internationally collected data on incidence potentially inaccurate and confusing. In this paper, we review current understanding of the epidemiology and aetiology of unexpected deaths in infancy, and current hypotheses on the pathophysiology of the processes that may lead to death. We also review interventions that have been adopted, with variable degrees of effectiveness in efforts to reduce the numbers of deaths, and new approaches that offer the possibility of prevention in the future.

Genetic and Environmental Factors Affecting TNF-α Responses in Relation to Sudden Infant Death Syndrome

Dysregulation of the inflammatory responses has been suggested to contribute to the events leading to sudden infant deaths. Our objectives were (1) to analyze a single nucleotide polymorphism (SNP) associated with high levels of tumor necrosis factor-α (TNF-α) responses, TNF G-308A, in sudden infant death syndrome (SIDS) infants, SIDS and control parents, and ethnic groups with different incidences of SIDS; (2) the effects of two risk factors for SIDS, cigarette smoke and virus infection, on TNF-α responses; and (3) to assess effects of genotype, cigarette smoke, and gender on TNF-α responses to bacterial toxins identified in SIDS infants. TNF G-308A genotypes were determined by real-time polymerase chain reaction for SIDS infants from Australia, Germany, and Hungary; parents of SIDS infants and their controls; and populations with high (Aboriginal Australian), medium (Caucasian), and low (Bangladeshi) SIDS incidences. Leukocytes from Caucasian donors were stimulated in vitro with endotoxin or toxic shock syndrome toxin-1 (TSST-1). TNF-α responses were measured by L929 bioassay (IU/ml) and assessed in relation to genotype, smoking status, and gender. There was a significantly higher proportion of the minor allele AA genotype among Australian SIDS infants (6/24, 24%) compared to 3/62 (4.8%) controls (p = 0.03). There were no significant differences in TNF-α responses by TNF G-308A genotypes when assessed in relation to smoking status or gender. Given the rarity of the TNF G-308A A allele in Caucasian populations, the finding that 24% of the Australian SIDS infants tested had this genotype requires further investigation and cautious interpretation. Although non-smokers with the AA genotype had higher TNFα responses to both TSST-1 and endotoxin, there were too few subjects with this rare allele to obtain statistically valid results. No effects of genotype, smoking, or gender were observed for TNF-α responses to these toxins.

Effects of gender, cytokine gene polymorphisms and environmental factors on inflammatory responses

Previous studies have indicated that cytokine gene polymorphisms of Indigenous Australians were predominantly associated with strong pro-inflammatory responses. We tested the hypothesis that cells of donors with genetic profiles of inflammatory cytokine single nucleotide polymorphisms (SNPs) similar to Indigenous Australians produce higher pro-inflammatory responses. PBMCs from 14 donors with genetic profiles for a high risk of strong pro-inflammatory responses and 14 with low-risk profiles were stimulated with endotoxin and effects of gender, IFN-γ, cigarette smoke extract (CSE) and testosterone on cytokine responses analysed. Cytokines were calculated from standard curves (Luminex 2.3 software). No significant differences were associated with SNP profile alone. Lower pro-inflammatory responses were observed for cells from males with low- or high-risk profiles. For cells from females with high-risk profiles, anti-inflammatory IL-10 responses were significantly reduced. There was no effect of testosterone levels on responses from males. For females, results from IFN-γ-treated cells showed positive correlations between testosterone levels and IL-1β responses to endotoxin for both risk groups and TNF-α for the high-risk group. If interactions observed among CSE, IFN-γ, genetic background and testosterone reflect those in vivo, these might contribute to increased incidences of hospitalisations for infectious diseases among Indigenous women.

Cytokine Levels in Late Pregnancy: Are Female Infants Better Protected Against Inflammation?

Inflammatory responses have been implicated in several forms of infant deaths (sudden expected deaths and stillbirths) and the initiation of pre-term births. In this study, we examined matched samples of term maternal blood, cord blood, and amniotic fluid obtained from 24 elective cesarean deliveries for both pro- and anti-inflammatory cytokines thought to be important in maintaining a balanced response leading to successful pregnancy outcome. These included interleukin (IL)-1β, IL-6, IL-8, tumor necrosis factor-α (TNF-α), interferon-γ (IFN-γ), IL-10, and IL-1 receptor antagonist (IL-1ra). Amniotic fluid levels for each of the cytokines examined were significantly higher than those for cord blood or maternal plasma. While pro-inflammatory cytokines were higher in amniotic fluid associated with male fetuses compared with females, the major significant difference was higher levels of IL-1ra in amniotic fluid associated with female fetuses. Our study supports similar findings for cytokines during mid-trimester, which noted that amniotic fluid levels were higher than those in maternal blood. Our study suggests that maternal decidua secretes additional IL-ra in the presence of a female conceptus which improves the likelihood of a good outcome compared to pregnancies with male fetuses.

The Role of Infection and Inflammation in Stillbirths: Parallels with SIDS?

It has been suggested that stillbirths are part of the spectrum of infant deaths that includes sudden infant death syndrome (SIDS). This paper examines the hypothesis that risk factors associated with stillbirths might contribute to dysregulation of inflammatory responses to infections that could trigger the physiological responses leading to fetal loss. These include genetic factors (ethnic group, sex), environmental (infection, cigarette smoke, obesity), and developmental (testosterone levels) factors. Interactions between the genetic, environmental, and developmental risk factors are also considered, e.g., the excess of male stillborn infants in relation to the effects of testosterone levels during development on pro-inflammatory responses. In contrast to SIDS, inflammatory responses of both mother and fetus need to be considered. Approaches for examining the hypothesis are proposed.

Animal models for assessment of infection and inflammation: contributions to elucidating the pathophysiology of sudden infant death syndrome

Sudden infant death syndrome (SIDS) is still not well understood. It is defined as the sudden and unexpected death of an infant without a definitive cause. There are numerous hypotheses about the etiology of SIDS but the exact cause or causes have never been pinpointed. Examination of theoretical pathologies might only be possible in animal models. Development of these models requires consideration of the environmental and/or developmental risk factors often associated with SIDS, as they need to explain how the risk factors could contribute to the cause of death. These models were initially developed in common laboratory animals to test various hypotheses to explain these infant deaths – guinea pig, piglet, mouse, neonatal rabbit, and neonatal rat. Currently, there are growing numbers of researchers using genetically altered animals to examine specific areas of interest. This review describes the different systems and models developed to examine the diverse hypotheses for the cause of SIDS and their potential for defining a causal mechanism or mechanisms.

Virus Infections and Sudden Death in Infancy: The Role of Interferon-γ

Respiratory infections have been implicated in sudden infant death syndrome (SIDS). As interferon-γ (IFN-γ) is a major response to virus infection, we examined (1) the frequency of single nucleotide polymorphism (SNP), IFNG T + 874A, in SIDS infants, their parents, and ethnic groups with different incidences of SIDS; (2) model systems with a monocytic cell line (THP-1) and human peripheral blood monocytes (PBMC) for effects of levels of IFN-γ on inflammatory responses to bacterial antigens identified in SIDS; (3) interactions between genetic and environmental factors on IFN-γ responses. IFNG T + 874A genotypes were determined for SIDS infants from three countries; families who had a SIDS death; populations with high (Indigenous Australian), medium (Caucasian), and low (Bangladeshi) SIDS incidences. The effect of IFN-γ on cytokine responses to endotoxin was examined in model systems with THP-1 cells and human PBMC. The IFN-γ responses to endotoxin and toxic shock syndrome toxin (TSST-1) were assessed in relation to genotype, gender, and reported smoking. There was a marginal association with IFNG T + 874A genotype and SIDS (p = 0.06). Indigenous Australians had significantly higher proportions of the IFNG T + 874A SNP (TT) associated with high responses of IFN-γ. THP-1 cells showed a dose dependent effect of IFN-γ on cytokine responses to endotoxin. For PBMC, IFN-γ enhanced interleukin (IL)-1β, IL-6, and tumor necrosis factor-α responses but reduced IL-8 and IL-10 responses. Active smoking had a suppressive effect on baseline levels of IFN-γ. There was no effect of gender or genotype on IFN-γ responses to bacterial antigens tested; however, significant differences were observed between genotypes in relation to smoking. The results indicate virus infections contribute to dysregulation of cytokine responses to bacterial antigens and studies on physiological effects of genetic factors must include controls for recent or concurrent infection and exposure to cigarette smoke.

Effects of maternal inflammation and exposure to cigarette smoke on birth weight and delivery of preterm babies in a cohort of indigenous Australian women

Sudden infant death syndrome (SIDS), neonatal deaths, and deaths from infection are higher among Indigenous Australians. This study aimed to determine the effects of inflammatory responses and exposure to cigarette smoke, two important factors associated with sudden death in infancy, on preterm birth, and birth weight in a cohort of Indigenous mothers. Indigenous Australian women (n = 131) were recruited as part of a longitudinal study while attending antenatal care clinics during pregnancy; blood samples were collected up to three times in pregnancy. Serum cotinine, indicating exposure to cigarette smoke, was detected in 50.4% of mothers. Compared with non-Indigenous women, the cohort had 10 times the prevalence of antibodies to Helicobacter pylori (33 vs. 3%). Levels of immunoglobulin G, antibodies to H. pylori, and C-reactive protein (CRP) were all inversely correlated with gestational age (P < 0.05). CRP levels were positively associated with maternal body mass index (BMI; ρ = 0.449, P = 0.001). The effects of cigarette smoke (cotinine) and inflammation (CRP) were assessed in relation to risk factors for SIDS: gestational age at delivery and birth weight. Serum cotinine levels were negatively associated with birth weight (ρ = −0.37, P < 0.001), this correlation held true for both male (ρ = −0.39, P = 0.002) and female (ρ = −0.30, P = 0.017) infants. Cotinine was negatively associated with gestational age at delivery (ρ = −0.199, P = 0.023). When assessed by fetal sex, this was significant only for males (ρ = −0.327, P = 0.011). CRP was negatively associated with gestational age at delivery for female infants (ρ = −0.46, P < 0.001). In contrast, maternal BMI was significantly correlated with birth weight. These data highlight the importance of putting programs in place to reduce cigarette smoke exposure in pregnancy and to treat women with chronic infections such as H. pylori to improve pregnancy outcomes and decrease risk factors for sudden death in infancy.

Exploring the risk factors for sudden infant deaths and their role in inflammatory responses to infection

The risk factors for sudden infant death syndrome (SIDS) parallel those associated with susceptibility to or severity of infectious diseases. There is no evidence that a single infectious agent is associated with SIDS; the common thread appears to be induction of inflammatory responses to infections. In this review, interactions between genetic and environmental risk factors for SIDS are assessed in relation to the hypothesis that many infant deaths result from dysregulation of inflammatory responses to "minor" infections. Risk factors are assessed in relation to three important stages of infection: (1) bacterial colonization (frequency or density); (2) induction of temperature-dependent toxins; (3) induction or control of inflammatory responses. In this article, we review the interactions among risk factors for SIDS for their effects on induction or control of inflammatory responses. The risk factors studied are genetic factors (sex, cytokine gene polymorphisms among ethnic groups at high or low risk of SIDS); developmental stage (changes in cortisol and testosterone levels associated with 2- to 4-month age range); environmental factors (virus infection, exposure to cigarette smoke). These interactions help to explain differences in the incidences of SIDS observed between ethnic groups prior to public health campaigns to reduce these infant deaths.