Trends in socioeconomic inequalities in risk of sudden infant death syndrome, other causes of infant mortality, and stillbirth in Scotland: population based study

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.

Investigation of possible causes of increase in Hungarian infant mortality in 2019

Összefoglaló. Bevezetés: Magyarországon a csecsemőhalandóság 2014 óta folyamatosan javult, azonban 2019-ben az előző évi adathoz képest 11%-kal magasabb érték mutatkozott. Célkitűzés: A vizsgálat célja a 2019. évi kedvezőtlenebb csecsemőhalálozási mutató lehetséges összetevőinek feltárása. Módszer: A 2018. és 2019. évi csecsemőhalálozási adatokat hasonlítottuk össze a csecsemő kora, a halál oka és a gyógyintézeti, illetve nem gyógyintézeti elhalálozás szerint. A vizsgálathoz a Központi Statisztikai Hivatal adatait használtuk. A trendvizsgálatnál 2010-től elemeztük az adatokat. A nem gyógyintézeti haláleseteket 10 évre összevonva járásonként térképesen ábrázoltuk. Eredmények: 2018-ban 304, 2019-ben 335 csecsemő halt meg Magyarországon, a csecsemőhalálozási arányszám 3,4 ezrelékről 3,8 ezrelékre emelkedett. A 2019. évi érték az előző évtizedek trendjére illesztett görbe alapján megfelelt a várható értéknek. 2019-ben a 0-27 napos csecsemőhalálozás alig változott a 2018. évihez képest, a 28-364 napos korban bekövetkezett halálesetek száma viszont növekedett. A vizsgált évben 59%-kal emelkedett a nem gyógyintézeti csecsemőhalálozás. A 2019. évi csecsemőhalálozás növekedéséért 74%-ban a nem gyógyintézeti esetek voltak felelősek. A nem gyógyintézeti halálozás döntő többsége késői csecsemőkorban következett be. A járásonkénti, 10 évre összevont, nem intézményben elhunyt csecsemők számában és 1000 élve születésre vonatkozó arányában ötszörös területi különbségek mutatkoztak. A halálokok közül a perinatalis szakban keletkező bizonyos állapotok miatt meghalt csecsemők száma emelkedett a leginkább, a nem gyógyintézeti halálozás esetében pedig a hirtelen csecsemőhalál szindrómában meghaltaké. Következtetés: 2019-ben kiugróan magas volt a nem gyógyintézeti, késői csecsemőhalálozás száma és részaránya, ezen esetek feltűnő regionális halmozódást mutattak. A csecsemőhalandóság csökkentésének hatásos eszköze lehetne a jövőben minden egyes csecsemőhalál részletes szakmai értékelése. Orv Hetil. 2021; 162(1): 830-838.

SUMMARY

INTRODUCTION

In Hungary, infant mortality has been steadily declining since 2014, but in 2019 it increased by 11% compared to 2018.

OBJECTIVE

The aim of our study is to explore the possible components of the above increase.

METHOD

Ten-year trends of infant mortality were analized and compared by age, cause, place of deaths (hospital or non-hospital environment) and location, using Central Statistical Office data.

RESULTS

There were 304 infant deaths in Hungary in 2018 and 335 in 2019. Infant mortality rate rose from 3.4‰ to 3.8‰, however, it was in line with the expected value based on the curve fitted to the trend of previous decades. In 2019, 0-27-day infant mortality basically did not change compared to 2018, while the number of deaths at 28-364 days of age increased. Non-hospital infant mortality increased by 59% in 2019 and these cases accounted for 74% of the total increase in infant mortality; the vast majority of these deaths occurred in late infancy. There were fivefold regional differences in the number of non-hospital infant deaths. Among the causes of death, the conditions related to the perinatal period and sudden infant death syndrome increased the most.

CONCLUSION

In Hungary, the number and proportion of non-hospital infant mortality was remarkably high in 2019 compared to previous years. These cases showed a striking regional accumulation. An effective tool for reducing infant mortality could be an appropriate professional assessment of each infant death in the future. Orv Hetil. 2021; 162(21): 830-838.

The socio-economic status of families experiencing the sudden unexpected death of an infant - Is it possibly related to a higher rate of non-natural deaths among them

Low socio-economic status is recognized as one of the risk factors for SIDS. In this study we have pointed out the similarities between families that have SIDS cases and families in which infant non-accidental injury has been proven, as well as the differences between them and the general population. This study was conducted in Montenegro, comparing 30 cases of SIDS with 25 cases of known infanticides and with a control group (60 cases) consisting of live newborns and their mothers from the general population, randomly selected from hospital-born newborns without exclusion criteria. We combined and compared the infant characteristics and mother characteristics between the above cases. There were significant similarities between the SIDS group and the infanticide group in terms of the following characteristics: the education level of the mothers (p = 0.086); maternal employment (p = 0.278); and place of residence (p = 0.269); while there were differences between the two groups regarding hospital birth (p = 0.027) and marital status (p = 0.011). The SIDS and infanticide groups, combined, had higher incidences of: out-of-hospital deliveries (p < 0.001); uneducated mothers (p < 0.001); unemployed mothers (p < 0.001); low socio-economic status (p < 0.001); and cases outside of marriage (p < 0.001), compared to the control groups. This study indicated a possible higher incidence of non-natural death among SIDS cases, as reflected by low socio-economic status and linked attributes, which is explained by their similarities with the infanticide groups and differences with the control groups.

County Poverty, Urban-Rural Classification, and the Causes of Term Infant Death : United States, 2012-2015

OBJECTIVE

Higher mortality among full-term infants (term infant deaths) contributes to disparities in infant mortality between the United States and other developed countries. We examined differences in the causes of term infant deaths across county poverty levels and urban-rural classification to understand underlying mechanisms through which these factors may act.

METHODS

We linked period birth/infant death files for 2012-2015 with US Census poverty estimates and county urban-rural classifications. We grouped the causes of term infant deaths as sudden unexpected death in infancy (SUDI), congenital malformations, perinatal conditions, and all other causes. We computed the distribution and relative risk of overall and cause-specific term infant mortality rates (term IMRs) per 1000 live births and 95% CIs for county-level factors.

RESULTS

The increase in term IMR across county poverty and urban-rural classification was mostly driven by an increase in the rate of SUDI. The relative risk of term infant deaths as a result of SUDI was 1.6 (95% CI, 1.5-1.8) times higher in medium-poverty counties and 2.3 (95% CI, 1.2-2.5) times higher in high-poverty counties than in low-poverty counties. Cause-specific IMRs of congenital malformations, perinatal conditions, and death from other causes did not differ by county poverty level. We found similar trends across county urban-rural classification. Sudden infant death syndrome was the main cause of SUDI across both county poverty levels and urban-rural classifications, followed by unknown causes and accidental suffocation and strangulation in bed.

CONCLUSIONS

Interventions aimed at reducing SUDI, particularly in high-poverty and rural areas, could have a major effect on reducing term IMR disparities between the United States and other developed countries.

Developing a national birth cohort for child health research using a hospital admissions database in England: The impact of changes to data collection practices

BACKGROUND

National birth cohorts derived from administrative health databases constitute unique resources for child health research due to whole country coverage, ongoing follow-up and linkage to other data sources. In England, a national birth cohort can be developed using Hospital Episode Statistics (HES), an administrative database covering details of all publicly funded hospital activity, including 97% of births, with longitudinal follow-up via linkage to hospital and mortality records. We present methods for developing a national birth cohort using HES and assess the impact of changes to data collection over time on coverage and completeness of linked follow-up records for children.

METHODS

We developed a national cohort of singleton live births in 1998-2015, with information on key risk factors at birth (birth weight, gestational age, maternal age, ethnicity, area-level deprivation). We identified three changes to data collection, which could affect linkage of births to follow-up records: (1) the introduction of the "NHS Numbers for Babies (NN4B)", an on-line system which enabled maternity staff to request a unique healthcare patient identifier (NHS number) immediately at birth rather than at civil registration, in Q4 2002; (2) the introduction of additional data quality checks at civil registration in Q3 2009; and (3) correcting a postcode extraction error for births by the data provider in Q2 2013. We evaluated the impact of these changes on trends in two outcomes in infancy: hospital readmissions after birth (using interrupted time series analyses) and mortality rates (compared to published national statistics).

RESULTS

The cohort covered 10,653,998 babies, accounting for 96% of singleton live births in England in 1998-2015. Overall, 2,077,929 infants (19.5%) had at least one hospital readmission after birth. Readmission rates declined by 0.2% percentage points per annual quarter in Q1 1998 to Q3 2002, shifted up by 6.1% percentage points (compared to the expected value based on the trend before Q4 2002) to 17.7% in Q4 2002 when NN4B was introduced, and increased by 0.1% percentage points per annual quarter thereafter. Infant mortality rates were under-reported by 16% for births in 1998-2002 and similar to published national mortality statistics for births in 2003-2015. The trends in infant readmission were not affected by changes to data collection practices in Q3 2009 and Q2 2013, but the proportion of unlinked mortality records in HES and in ONS further declined after 2009.

DISCUSSION

HES can be used to develop a national birth cohort for child health research with follow-up via linkage to hospital and mortality records for children born from 2003 onwards. Re-linking births before 2003 to their follow-up records would maximise potential benefits of this rich resource, enabling studies of outcomes in adolescents with over 20 years of follow-up.

Applying a Social Exclusion Framework to Explore the Relationship Between Sudden Unexpected Deaths in Infancy (SUDI) and Social Vulnerability

Background: Sudden Unexpected Death in Infancy (SUDI) is a leading cause of preventable infant mortality and strongly associated with social adversity. While this has been noted over many decades, most previous studies have used single economic markers in social disadvantage analyses. To date there have been no previous attempts to analyze the cumulative effect of multiple adversities in combination on SUDI risk.

Methods: Based on sociological theories of social exclusion, a multidimensional framework capable of producing an overall measure of family-level social vulnerability was developed, accounting for both increasing disadvantage with increasing prevalence among family members and effect of family structures. This framework was applied retrospectively to all cases of SUDI that occurred in Queensland between 2010 and 2014. Additionally, an exploratory factor analysis was performed to investigate whether differing “types” of vulnerability could be identified.

Results: Increased family vulnerability was associated with four major known risk factors for sudden infant death: smoking, surface sharing, not-breastfeeding and use of excess bedding. However, families with lower levels of social vulnerability were more likely to display two major risk factors: prone infant sleep position and not room-sharing. There was a significant positive relationship between family vulnerability and the cumulative total of risk factors. Exploratory factor analysis identified three distinct vulnerability types (chaotic lifestyle, socioeconomic and psychosocial); the first two were associated with presence of major SUDI risk factors. Indigenous infants had significantly higher family vulnerability scores than non-Indigenous families.

Conclusion: A multidimensional measure that captures adversity across a range of indicators highlights the need for proportionate universalism to reduce the stalled rates of sudden infant death. In addition to information campaigns continuing to promote the importance of the back-sleeping position and close infant-caregiver proximity, socially vulnerable families should be a priority population for individually tailored or community based multi-model approaches.

Assessing the deprivation gap in stillbirths and neonatal deaths by cause of death: a national population-based study

OBJECTIVE

To investigate socioeconomic inequalities in cause-specific stillbirth and neonatal mortality to identify key areas of focus for future intervention strategies to achieve government ambitions to reduce mortality rates.

DESIGN

Retrospective cohort study.

SETTING

England, Wales, Scotland and the UK Crown Dependencies.

PARTICIPANTS

All singleton births between 1 January 2014 and 31 December 2015 at ≥24 weeks' gestation.

MAIN OUTCOME MEASURE

Cause-specific stillbirth or neonatal death (0-27 days after birth) per 10 000 births by deprivation quintile.

RESULTS

Data on 5694 stillbirths (38.1 per 10 000 total births) and 2368 neonatal deaths (15.9 per 10 000 live births) were obtained from Mothers and Babies: Reducing Risk through Audits and Confidential Enquiries across the UK (MBRRACE-UK). Women from the most deprived areas were 1.68 (95% CI 1.56 to 1.81) times more likely to experience a stillbirth and 1.67 (95% CI 1.48 to 1.87) times more likely to experience a neonatal death than those from the least deprived areas, equating to an excess of 690 stillbirths and 231 neonatal deaths per year associated with deprivation. Small for gestational age (SGA) unexplained antepartum stillbirth was the greatest contributor to excess stillbirths accounting for 33% of the deprivation gap in stillbirths. Congenital anomalies accounted for the majority (59%) of the deprivation gap in neonatal deaths, followed by preterm birth not SGA (24-27 weeks, 27%).

CONCLUSIONS

Cause-specific mortality rates at a national level allow identification of key areas of focus for future intervention strategies to reduce mortality. Despite a reduction in the deprivation gap for stillbirths and neonatal deaths, public health interventions should primarily focus on socioeconomic determinants of SGA stillbirth and congenital anomalies.

Inequalities and stillbirth in the UK: a meta-narrative review

OBJECTIVE

To review what is known about the relationship between stillbirth and inequalities from different disciplinary perspectives to inform stillbirth prevention strategies.

DESIGN

Systematic review using the meta-narrative method.

SETTING

Studies undertaken in the UK.

DATA SOURCES

Scoping phase: experts in field, exploratory electronic searches and handsearching. Systematic searches phase: Nine databases with no geographical or date restrictions. Non-English language studies were excluded.

STUDY SELECTION

Any investigation of stillbirth and inequalities with a UK component.

DATA EXTRACTION AND SYNTHESIS

Three authors extracted data and assessed study quality. Data were summarised, tabulated and presented graphically before synthesis of the unfolding storyline by research tradition; and then of the commonalities, differences and interplays between narratives into resultant summary meta-themes.

RESULTS

Fifty-four sources from nine distinctive research traditions were included. The evidence of associations between social inequalities and stillbirth spanned 70 years. Across research traditions, there was recurrent evidence of the social gradient remaining constant or increasing, fuelling repeated calls for action (meta-theme 1: something must be done). There was less evidence of an effective response to these calls. Data pertaining to socioeconomic, area and ethnic disparities were routinely collected, but not consistently recorded, monitored or reported in relation to stillbirth (meta-theme 2: problems of precision). Many studies stressed the interplay of socioeconomic status, deprivation or ethnicity with aggregated factors including heritable, structural, environmental and lifestyle factors (meta-theme 3: moving from associations towards intersectionality and intervention(s)). No intervention studies were identified.

CONCLUSION

Research investigating inequalities and stillbirth in the UK is underdeveloped. This is despite repeated evidence of an association between stillbirth risk and poverty, and stillbirth risk, poverty and ethnicity. A specific research forum is required to lead the development of research and policy in this area, which can harness the multiple relevant research perspectives and address the intersections between different policy areas.

PROSPERO REGISTRATION NUMBER

CRD42017079228.

Three decades of inequality in neonatal and early childhood mortality in singleton births in Scotland

Background

Socioeconomic inequality in child mortality highlights opportunities for policies to reduce child deaths.

Methods

We used singleton birth, death and maternity records from Scotland, 1981-2011, to examine mortality rate differences by age across deprivation quintiles over time. We measured the difference between the most and least deprived quintiles (Q5-Q1) and the slope index of inequality (SII) across all quintiles-measures of the absolute deprivation gap, providing an indication of the public health impact.

Results

Q5-Q1 remained relatively constant from 1990 onwards for early neonates, widened in the mid-2000s for late neonates, increased in the 1990 s then decreased in the 2000 s in the post-neonates and declined over time in early childhood. The trend over time in SII showed no significant change for early neonates (P = 0.440), significant decrease for post-neonates (P = 0.010) and early childhood (P = 0.043), and significant increase for late neonates (P = 0.011).

Conclusions

Over three decades, the absolute deprivation gap in mortality widened in late neonates but stabilized or declined at other ages. This may reflect improved survival beyond the early neonatal period of babies with conditions related to socioeconomic inequality such as prematurity. Monitoring birth cohort data could enhance understanding of this vulnerable group.

Mediating roles of preterm birth and restricted fetal growth in the relationship between maternal education and infant mortality: A Danish population-based cohort study

BACKGROUND

Socioeconomic disparities in infant mortality have persisted for decades in high-income countries and may have become stronger in some populations. Therefore, new understandings of the mechanisms that underlie socioeconomic differences in infant deaths are essential for creating and implementing health initiatives to reduce these deaths. We aimed to explore whether and the extent to which preterm birth (PTB) and small for gestational age (SGA) at birth mediate the association between maternal education and infant mortality.

METHODS AND FINDINGS

We developed a population-based cohort study to include all 1,994,618 live singletons born in Denmark in 1981-2015. Infants were followed from birth until death, emigration, or the day before the first birthday, whichever came first. Maternal education at childbirth was categorized as low, medium, or high. An inverse probability weighting of marginal structural models was used to estimate the controlled direct effect (CDE) of maternal education on offspring infant mortality, further split into neonatal (0-27 days) and postneonatal (28-364 days) deaths, and portion eliminated (PE) by eliminating mediation by PTB and SGA. The proportion eliminated by eliminating mediation by PTB and SGA was reported if the mortality rate ratios (MRRs) of CDE and PE were in the same direction. The MRRs between maternal education and infant mortality were 1.63 (95% CI 1.48-1.80, P < 0.001) and 1.19 (95% CI 1.08-1.31, P < 0.001) for low and medium versus high education, respectively. The estimated proportions of these total associations eliminated by reducing PTB and SGA together were 55% (MRRPE = 1.27, 95% CI 1.15-1.40, P < 0.001) for low and 60% (MRRPE = 1.11, 95% CI 1.01-1.22, P = 0.037) for medium versus high education. The proportions eliminated by eliminating PTB and SGA separately were, respectively, 46% and 11% for low education (versus high education) and 48% and 13% for medium education (versus high education). PTB and SGA together contributed more to the association of maternal educational disparities with neonatal mortality (proportion eliminated: 75%-81%) than with postneonatal mortality (proportion eliminated: 21%-23%). Limitations of the study include the untestable assumption of no unmeasured confounders for the causal mediation analysis, and the limited generalizability of the findings to other countries with varying disparities in access and quality of perinatal healthcare.

CONCLUSIONS

PTB and SGA may play substantial roles in the relationship between low maternal education and infant mortality, especially for neonatal mortality. The mediating role of PTB appeared to be much stronger than that of SGA. Public health strategies aimed at reducing neonatal mortality in high-income countries may need to address socially related prenatal risk factors of PTB and impaired fetal growth. The substantial association of maternal education with postneonatal mortality not accounted for by PTB or SGA could reflect unaddressed educational disparities in infant care or other factors.

The DESiGN trial (DEtection of Small for Gestational age Neonate), evaluating the effect of the Growth Assessment Protocol (GAP): study protocol for a randomised controlled trial

Background

Stillbirth rates in the United Kingdom (UK) are amongst the highest of all developed nations. The association between small-for-gestational-age (SGA) foetuses and stillbirth is well established, and observational studies suggest that improved antenatal detection of SGA babies may halve the stillbirth rate. The Growth Assessment Protocol (GAP) describes a complex intervention that includes risk assessment for SGA and screening using customised fundal-height growth charts. Increased detection of SGA from the use of GAP has been implicated in the reduction of stillbirth rates by 22%, in observational studies of UK regions where GAP uptake was high. This study will be the first randomised controlled trial examining the clinical efficacy, health economics and implementation of the GAP programme in the antenatal detection of SGA.

Methods/design

In this randomised controlled trial, clusters comprising a maternity unit (or National Health Service Trust) were randomised to either implementation of the GAP programme, or standard care. The primary outcome is the rate of antenatal ultrasound detection of SGA in infants found to be SGA at birth by both population and customised standards, as this is recognised as being the group with highest risk for perinatal morbidity and mortality. Secondary outcomes include antenatal detection of SGA by population centiles, antenatal detection of SGA by customised centiles, short-term maternal and neonatal outcomes, resource use and economic consequences, and a process evaluation of GAP implementation. Qualitative interviews will be performed to assess facilitators and barriers to implementation of GAP.

Discussion

This study will be the first to provide data and outcomes from a randomised controlled trial investigating the potential difference between the GAP programme compared to standard care for antenatal ultrasound detection of SGA infants. Accurate information on the performance and service provision requirements of the GAP protocol has the potential to inform national policy decisions on methods to reduce the rate of stillbirth.

Trial registration

Primary registry and trial identifying number: ISRCTN 67698474. Registered on 2 November 2016.

Electronic supplementary material

The online version of this article (10.1186/s13063-019-3242-6) contains supplementary material, which is available to authorized users.

Blinded ultrasound fetal biometry at 36 weeks and risk of emergency Cesarean delivery in a prospective cohort study of low-risk nulliparous women

OBJECTIVES

To compare the association between risk of emergency Cesarean delivery (CD) and non-customized vs customized ultrasound estimated fetal weight (EFW) at 36 weeks' gestation, determine whether addition of ultrasound EFW to a model based on maternal characteristics alone improved prediction of emergency CD, assess the screening performance of a multivariable model using both EFW and maternal characteristics to predict emergency CD, and determine whether women at high predicted risk of emergency CD based on this model had higher risk of maternal and perinatal morbidity compared with screen-negative women.

METHODS

We studied 3047 low-risk (no pre-existing medical conditions or acquired complications of pregnancy) nulliparous women from the prospective Pregnancy Outcome Prediction study (Cambridge, UK) cohort, who underwent ultrasound EFW at ∼36 weeks' gestation. Both the women and their clinicians were blinded to fetal biometry results. Emergency CD was defined as delivery by Cesarean section in pregnancies in which the date of delivery had not been prearranged. Additional candidate predictors of emergency CD evaluated were maternal age, height, body mass index (BMI), weight gain, fetal abdominal circumference growth velocity and fetal sex. External validation of the predictive model was performed using routinely collected data from 55 337 births in Scotland between 2003 and 2008. Women with an estimated risk of emergency CD ≥ 40% were defined as screen positive.

RESULTS

Blinded EFW was associated strongly with the risk of emergency CD (coefficient for increase of 1 SD in EFW, 0.39 (95% CI, 0.30-0.48); odds ratio (OR), 1.48 (95% CI, 1.35-1.62)). The coefficient for customized EFW was similar (0.42 (95% CI, 0.33-0.51); OR, 1.53 (95% CI, 1.39-1.67)); hence, for simplicity, non-customized EFW was employed subsequently. A multivariable logistic regression model combining maternal characteristics (age, height, BMI and weight gain between 12 and 36 weeks) was moderately predictive of emergency CD (area under the receiver-operating characteristics curve (AUC) = 0.68). Addition of blinded EFW to the model increased the AUC to 0.71 and improved prediction (likelihood-ratio test P < 0.0001). Based on this model, 189 (6.2%) women were screen positive and 48% of these delivered by CD. Screen-positive women had elevated risks of severe postpartum hemorrhage (relative risk (RR), 2.49; 95% CI, 1.83-3.38), any adverse neonatal outcome (RR, 1.86; 95% CI, 1.22-2.82) and severe adverse neonatal outcome (RR, 4.03; 95% CI, 1.35-12.03) compared with screen-negative women. The risks of these events were also higher compared with women who had a term CD for breech presentation. The model was similarly predictive of the risk of emergency CD and perinatal morbidity when evaluated using the dataset from Scotland.

CONCLUSIONS

Ultrasound EFW at 36 weeks, combined with maternal characteristics, can identify women who are at increased risk of subsequent emergency CD. These women are at increased risk of maternal and perinatal morbidity compared with women at low risk of emergency CD and those having CD for breech presentation at term. Copyright © 2017 ISUOG. Published by John Wiley & Sons Ltd.

Causes of death and infant mortality rates among full-term births in the United States between 2010 and 2012: An observational study

BACKGROUND

While the high prevalence of preterm births and its impact on infant mortality in the US have been widely acknowledged, recent data suggest that even full-term births in the US face substantially higher mortality risks compared to European countries with low infant mortality rates. In this paper, we use the most recent birth records in the US to more closely analyze the primary causes underlying mortality rates among full-term births.

METHODS AND FINDINGS

Linked birth and death records for the period 2010-2012 were used to identify the state- and cause-specific burden of infant mortality among full-term infants (born at 37-42 weeks of gestation). Multivariable logistic models were used to assess the extent to which state-level differences in full-term infant mortality (FTIM) were attributable to observed differences in maternal and birth characteristics. Random effects models were used to assess the relative contribution of state-level variation to FTIM. Hypothetical mortality outcomes were computed under the assumption that all states could achieve the survival rates of the best-performing states. A total of 10,175,481 infants born full-term in the US between January 1, 2010, and December 31, 2012, were analyzed. FTIM rate (FTIMR) was 2.2 per 1,000 live births overall, and ranged between 1.29 (Connecticut, 95% CI 1.08, 1.53) and 3.77 (Mississippi, 95% CI 3.39, 4.19) at the state level. Zero states reached the rates reported in the 6 low-mortality European countries analyzed (FTIMR < 1.25), and 13 states had FTIMR > 2.75. Sudden unexpected death in infancy (SUDI) accounted for 43% of FTIM; congenital malformations and perinatal conditions accounted for 31% and 11.3% of FTIM, respectively. The largest mortality differentials between states with good and states with poor FTIMR were found for SUDI, with particularly large risk differentials for deaths due to sudden infant death syndrome (SIDS) (odds ratio [OR] 2.52, 95% CI 1.86, 3.42) and suffocation (OR 4.40, 95% CI 3.71, 5.21). Even though these mortality differences were partially explained by state-level differences in maternal education, race, and maternal health, substantial state-level variation in infant mortality remained in fully adjusted models (SIDS OR 1.45, suffocation OR 2.92). The extent to which these state differentials are due to differential antenatal care standards as well as differential access to health services could not be determined due to data limitations. Overall, our estimates suggest that infant mortality could be reduced by 4,003 deaths (95% CI 2,284, 5,587) annually if all states were to achieve the mortality levels of the best-performing state in each cause-of-death category. Key limitations of the analysis are that information on termination rates at the state level was not available, and that causes of deaths may have been coded differentially across states.

CONCLUSIONS

More than 7,000 full-term infants die in the US each year. The results presented in this paper suggest that a substantial share of these deaths may be preventable. Potential improvements seem particularly large for SUDI, where very low rates have been achieved in a few states while average mortality rates remain high in most other areas. Given the high mortality burden due to SIDS and suffocation, policy efforts to promote compliance with recommended sleeping arrangements could be an effective first step in this direction.

How can we make international comparisons of infant mortality in high income countries based on aggregate data more relevant to policy?

Background

Infant mortality rates are commonly used to compare the health of populations. Observed differences are often attributed to variation in child health care quality. However, any differences are at least partly explained by variation in the prevalence of risk factors at birth, such as low birth weight. This distinction is important for designing interventions to reduce infant mortality. We suggest a simple method for decomposing inter-country differences in crude infant mortality rates into two metrics representing risk factors operating before and after birth.

Methods

We used data from 7 European countries participating in the EURO-PERISTAT project in 2010. We calculated crude and birth weight-standardised stillbirth and infant mortality rates using Norway as the standard population. We decomposed between-country differences in crude stillbirth and infant mortality rates into the within-country difference in crude and birth weight-standardised stillbirth and infant mortality rates (metric 1), reflecting prenatal risk factors, and the between-country difference in birth weight-standardised stillbirth and infant mortality rates (metric 2), reflecting risk factors operating after birth. We also calculated birth weight-specific mortality.

Results

Using our metrics, we showed that for England, Wales and Scotland risk factors before and after birth contributed equally to the differences in crude stillbirth and infant mortality rates relative to Norway. In Austria, Czech Republic and Switzerland the differences were driven primarily by metric 1, reflecting high rate of low birth weight. The highest values of metric 2 observed in Poland partially reflected high rates of congenital anomalies.

Conclusions

Our suggested metrics can be used to guide policy decisions on preventing infant deaths through reducing risk factors at birth or improving the care of babies after birth. Aggregate data tabulated by birth weight/gestational age should be routinely collected and published in high-income countries where birth weight is reported on birth certificates.

Electronic supplementary material

The online version of this article (10.1186/s12884-017-1622-z) contains supplementary material, which is available to authorized users.

Understanding determinants of unequal distribution of stillbirth in Tehran, Iran: a concentration index decomposition approach

OBJECTIVE

The present inquiry set to determine the economic inequality in history of stillbirth and understanding determinants of unequal distribution of stillbirth in Tehran, Iran.

METHODS

A population-based cross-sectional study was conducted on 5170 pregnancies in Tehran, Iran, since 2015. Principal component analysis (PCA) was applied to measure the asset-based economic status. Concentration index was used to measure socioeconomic inequality in stillbirth and then decomposed into its determinants.

RESULTS

The concentration index and its 95% CI for stillbirth was -0.121 (-0.235 to -0.002). Decomposition of the concentration index showed that mother's education (50%), mother's occupation (30%), economic status (26%) and father's age (12%) had the highest positive contributions to measured inequality in stillbirth history in Tehran. Mother's age (17%) had the highest negative contribution to inequality.

CONCLUSIONS

Stillbirth is unequally distributed among Iranian women and is mostly concentrated among low economic status people. Mother-related factors had the highest positive and negative contributions to inequality, highlighting specific interventions for mothers to redress inequality.

Seeking order amidst chaos: a systematic review of classification systems for causes of stillbirth and neonatal death, 2009-2014

BACKGROUND

Each year, about 5.3 million babies die in the perinatal period. Understanding of causes of death is critical for prevention, yet there is no globally acceptable classification system. Instead, many disparate systems have been developed and used. We aimed to identify all systems used or created between 2009 and 2014, with their key features, including extent of alignment with the International Classification of Diseases (ICD) and variation in features by region, to inform the World Health Organization's development of a new global approach to classifying perinatal deaths.

METHODS

A systematic literature review (CINAHL, EMBASE, Medline, Global Health, and PubMed) identified published and unpublished studies and national reports describing new classification systems or modifications of existing systems for causes of perinatal death, or that used or tested such systems, between 2009 and 2014. Studies reporting ICD use only were excluded. Data were independently double-extracted (except from non-English publications). Subgroup analyses explored variation by extent and region.

RESULTS

Eighty-one systems were identified as new, modifications of existing systems, or having been used between 2009 and 2014, with an average of ten systems created/modified each year. Systems had widely varying characteristics: (i) comprehensiveness (40 systems classified both stillbirths and neonatal deaths); (ii) extent of use (systems were created in 28 countries and used in 40; 17 were created for national use; 27 were widely used); (iii) accessibility (three systems available in e-format); (iv) underlying cause of death (64 systems required a single cause of death); (v) reliability (10 systems tested for reliability, with overall Kappa scores ranging from .35-.93); and (vi) ICD alignment (17 systems used ICD codes). Regional databases were not searched, so system numbers may be underestimated. Some non-differential misclassification of systems was possible.

CONCLUSIONS

The plethora of systems in use, and continuing system development, hamper international efforts to improve understanding of causes of death. Recognition of the features of currently used systems, combined with a better understanding of the drivers of continued system creation, may help the development of a truly effective global system.

Screening and prevention of stillbirth

Stillbirth is delivery of a baby at or after 24 weeks of gestational age (UK definition) not showing any signs of life. It affects almost one in 200 pregnancies and is the single major cause of perinatal death. Stillbirth is associated with a wide range of maternal demographic characteristics, but most of the variations in stillbirth risk are independent of these characteristics. Stillbirth is the end point of multiple processes, but the single most common cause is probably placental dysfunction. Stillbirth is associated with a wide range of biochemical and ultrasonic predictors, but there is limited evidence to support population-based screening. However, the evidence based is weak due to the use of poorly characterised screening tests, the failure to couple risk assessment with a clearly effective intervention for those who screen positive and inadequate study sample sizes. Basic research needs to identify better predictors, and clinical trials need to adopt more rigorous methodologies.

Classification systems for causes of stillbirth and neonatal death, 2009-2014: an assessment of alignment with characteristics for an effective global system

Background

To reduce the burden of 5.3 million stillbirths and neonatal deaths annually, an understanding of causes of deaths is critical. A systematic review identified 81 systems for classification of causes of stillbirth (SB) and neonatal death (NND) between 2009 and 2014. The large number of systems hampers efforts to understand and prevent these deaths. This study aimed to assess the alignment of current classification systems with expert-identified characteristics for a globally effective classification system.

Methods

Eighty-one classification systems were assessed for alignment with 17 characteristics previously identified through expert consensus as necessary for an effective global system. Data were extracted independently by two authors. Systems were assessed against each characteristic and weighted and unweighted scores assigned to each. Subgroup analyses were undertaken by system use, setting, type of death included and type of characteristic.

Results

None of the 81 systems were aligned with more than 9 of the 17 characteristics; most (82 %) were aligned with four or fewer. On average, systems were aligned with 19 % of characteristics. The most aligned system (Frøen 2009-Codac) still had an unweighted score of only 9/17. Alignment with individual characteristics ranged from 0 to 49 %. Alignment was somewhat higher for widely used as compared to less used systems (22 % v 17 %), systems used only in high income countries as compared to only in low and middle income countries (20 % vs 16 %), and systems including both SB and NND (23 %) as compared to NND-only (15 %) and SB-only systems (13 %). Alignment was higher with characteristics assessing structure (23 %) than function (15 %).

Conclusions

There is an unmet need for a system exhibiting all the characteristics of a globally effective system as defined by experts in the use of systems, as none of the 81 contemporary classification systems assessed was highly aligned with these characteristics. A particular concern in terms of global effectiveness is the lack of alignment with “ease of use” among all systems, including even the most-aligned. A system which meets the needs of users would have the potential to become the first truly globally effective classification system.

Electronic supplementary material

The online version of this article (doi:10.1186/s12884-016-1040-7) contains supplementary material, which is available to authorized users.

Socioeconomic inequalities in stillbirth rates in Europe: measuring the gap using routine data from the Euro-Peristat Project

BACKGROUND

Previous studies have shown that socioeconomic position is inversely associated with stillbirth risk, but the impact on national rates in Europe is not known. We aimed to assess the magnitude of social inequalities in stillbirth rates in European countries using indicators generated from routine monitoring systems.

METHODS

Aggregated data on the number of stillbirths and live births for the year 2010 were collected for three socioeconomic indicators (mothers' educational level, mothers' and fathers' occupational group) from 29 European countries participating in the Euro-Peristat project. Educational categories were coded using the International Standard Classification of Education (ISCED) and analysed as: primary/lower secondary, upper secondary and postsecondary. Parents' occupations were grouped using International Standard Classification of Occupations (ISCO-08) major groups and then coded into 4 categories: No occupation or student, Skilled/ unskilled workers, Technicians/clerical/service occupations and Managers/professionals. We calculated risk ratios (RR) for stillbirth by each occupational group as well as the percentage population attributable risks using the most advantaged category as the reference (post-secondary education and professional/managerial occupations).

RESULTS

Data on stillbirth rates by mothers' education were available in 19 countries and by mothers' and fathers' occupations in 13 countries. In countries with these data, the median RR of stillbirth for women with primary and lower secondary education compared to women with postsecondary education was 1.9 (interquartile range (IQR): 1.5 to 2.4) and 1.4 (IQR: 1.2 to 1.6), respectively. For mothers' occupations, the median RR comparing outcomes among manual workers with managers and professionals was 1.6 (IQR: 1.0-2.1) whereas for fathers' occupations, the median RR was 1.4 (IQR: 1.2-1.8). When applied to the entire set of countries with data about mothers' education, 1606 out of 6337 stillbirths (25 %) would not have occurred if stillbirth rates for all women were the same as for women with post-secondary education in their country.

CONCLUSIONS

Data on stillbirths and socioeconomic status from routine systems showed widespread and consistent socioeconomic inequalities in stillbirth rates in Europe. Further research is needed to better understand differences between countries in the magnitude of the socioeconomic gradient.

Social and behavioural factors in Non-suspicious unexpected death in infancy; experience from metropolitan police project indigo investigation

Background

Risk factors for Sudden Unexpected Death in Infancy (SUDI) are well described, and such cases are now investigated according to standard protocols. In London, Project Indigo of the Metropolitan Police provides a unique, detailed framework for such data collection. We investigate such data to provide a contemporary account of SUDI in a large city and further link data to publically available datasets to investigate interactions with social factors.

Methods

Retrospective analysis of data routinely collected by the Metropolitan Police Service in all cases of non-suspicious SUDI deaths in London during a six year period.

Results

SUDI deaths are associated with markers of social deprivation in London. A significant proportion of such deaths are associated with potentially modifiable risk factors such as cigarette smoking and co-sleeping, such behaviour also being associated with social factors, including accommodation issues.

Conclusions

Routinely collected data provide valuable insight into patterns and associations of mortality, with SUDI remaining a significant issue in London. Risk factors include social disadvantage, which may manifest in part by affecting behavioural patterns such as co-sleeping and public health interventions to reduce rates require significant social modification.

Ignored Disease or Diagnostic Dustbin? Sudden Infant Death Syndrome in the British Context

Sudden Infant Death Syndrome (SIDS) was defined in 1969 and incorporated into the International Classification of Diseases a decade later. To advocates of SIDS as a diagnosis, medical interest in sudden infant death was long overdue. However, the definition of SIDS lacked positive diagnostic criteria, provoking some to view it as a 'diagnostic dustbin' for the disposal of problematic cases where cause of death was unclear. This paper examines the development of medical interest in sudden infant death in Britain during the middle decades of the twentieth century. It highlights the importance of recognising the historicity of SIDS as a diagnosis facilitated by changes in law and medicine over the course of the nineteenth and twentieth centuries. It suggests that SIDS provides a definitive case study of the medicalisation of life and death, and a unique example of an officially recognised disease that had no symptoms, signs, pathology or patients.

UK Pakistani views on the adverse health risks associated with consanguineous marriages

This is a qualitative study exploring the perceptions of members from the Pakistani/Kashmiri community living in Luton, UK, on the adverse health risks associated with consanguineous marriages. Rates of stillbirths and infant mortality are higher than the national average in Luton and the existing evidence base suggests that these higher rates may be associated with consanguinity (especially first cousin marriages) in highly consanguineous populations, such as the Pakistani/Kashmiri ethnic group. This qualitative study included 9 focus groups and 10 one to one in-depth interviews (n = 58) with members from the Pakistani/Kashmiri community in Luton during 2012. Audio-recorded transcripts were analysed using framework analysis. Emerging themes included a limited knowledge, opposition to evidence and need for a more culturally sensitive health services approach. Findings from the focus group and interview discussions indicated that participants had a limited and varied understanding of genetic risk and indicated a lack of discussion within the community regarding genetic risk. They also opposed evidence that may link consanguineous marriages with infant mortality, stillbirth or genetic disorders that led to disability. The participants stressed the need for culturally sensitive and locally constructed services for information on genetic risk and services. These findings may be used to address higher rates of infant mortality and adverse health impacts associated with higher rates of consanguinity in Luton and elsewhere, through a partnership approach, improve upon current services and develop culturally appropriate services.

Understanding why children die in high-income countries

Many factors affect child and adolescent mortality in high-income countries. These factors can be conceptualised within four domains-intrinsic (biological and psychological) factors, the physical environment, the social environment, and service delivery. The most prominent factors are socioeconomic gradients, although the mechanisms through which they exert their effects are complex, affect all four domains, and are often poorly understood. Although some contributing factors are relatively fixed--including a child's sex, age, ethnic origin, and genetics, some parental characteristics, and environmental conditions--others might be amenable to interventions that could lessen risks and help to prevent future child deaths. We give several examples of health service features that could affect child survival, along with interventions, such as changes to the physical or social environment, which could affect upstream (distal) factors.

Review of methods for handling confounding by cluster and informative cluster size in clustered data

Clustered data are common in medical research. Typically, one is interested in a regression model for the association between an outcome and covariates. Two complications that can arise when analysing clustered data are informative cluster size (ICS) and confounding by cluster (CBC). ICS and CBC mean that the outcome of a member given its covariates is associated with, respectively, the number of members in the cluster and the covariate values of other members in the cluster. Standard generalised linear mixed models for cluster-specific inference and standard generalised estimating equations for population-average inference assume, in general, the absence of ICS and CBC. Modifications of these approaches have been proposed to account for CBC or ICS. This article is a review of these methods. We express their assumptions in a common format, thus providing greater clarity about the assumptions that methods proposed for handling CBC make about ICS and vice versa, and about when different methods can be used in practice. We report relative efficiencies of methods where available, describe how methods are related, identify a previously unreported equivalence between two key methods, and propose some simple additional methods. Unnecessarily using a method that allows for ICS/CBC has an efficiency cost when ICS and CBC are absent. We review tools for identifying ICS/CBC. A strategy for analysis when CBC and ICS are suspected is demonstrated by examining the association between socio-economic deprivation and preterm neonatal death in Scotland.

Risk factors and trends in the rate of stillbirth in Hungary between 1971 and 2010

OBJECTIVE

Possible risk factors and trends in the rate of stillbirth in Hungary between 1971 and 2010.

METHODS

Annual data of fetal birth weight, fetal gender, maternal age and marital status of the mother categories were available for both live and stillborn cases and were analyzed using negative binomial regression. A p value less than 0.05 was considered significant.

RESULTS

Male gender significantly increased risk of stillbirth (relative risk (RR):1.08; p < 0.001). The risk of stillbirth was also significantly associated with the maternal age (RR: 2.01 in the group older than 35 years, relative to younger mothers; p < 0.001), and the marital status (RR: 1.24 among the babies of an extramarital partnership; p < 0.001), this holding true for both fetal genders. However, a low birth weight ( < 2500 g) increased the risk of stillbirth more than 18-fold (RR: 18.47; p < 0.001) and there was a markedly higher risk of low birth weight in boys than in girls. Further, a strong negative correlation (r = -0.88) was detected between the real income per person of the overall population and the rate of stillbirth.

CONCLUSIONS

These findings support the known risk factors of stillbirth and gender-specific analyses given an estimation of the risk of stillbirth in both boys and girls.

Unravelling the enigma of Perthes disease

Perthes disease is an idiopathic avascular necrosis of a juvenile hip. Although 2010 marked a century since it was first described, the aetiology remains unknown. It is suggested that adverse socioeconomic circumstances may be a key precipitant. This work describes recent studies that explore the disease epidemiology. Descriptive studies include a case register from Merseyside, hospital discharge data from Scotland, analysis of the world's largest community disease register (General Practice Research Database [GPRD]) and a systematic review of incidence. Analytical studies include a nested case-controlled study in the GPRD and a hospital case-controlled study. The studies demonstrated a striking north-south divide in the UK incidence of Perthes disease, similar to that seen in many adult diseases. There was a sustained fall in disease frequency in all studies, with a narrowing of the north-south divide. There was a strong association with area deprivation, independent of living in an urban environment. Internationally, equatorial regions were unaffected by disease and northern Europe had the highest incidence, which was primarily a function of race although latitude was an independent predictor. Individual characteristics associated with the disease were congenital anomalies of the genitourinary tract and a structural abnormality of arterial calibre. Despite a falling incidence, Perthes disease remains an important cause of child morbidity and exemplifies socioeconomic inequalities. A deprivation-related exposure, acting early in development, appears critical. The aetiological factor in Perthes disease remains elusive but it is likely that unravelling this enigma may unlock additional secrets pertaining to the developmental origins of this and other diseases.

Neighbourhood income and neonatal, postneonatal and sudden infant death syndrome (SIDS) mortality in Canada, 1991-2005

BACKGROUND

Rates of infant mortality declined in Canada in the 1990s and 2000s, but the extent to which all socio-economic levels benefitted from this progress is unknown.

OBJECTIVES

This study investigated differences and time trends in neonatal, postneonatal and sudden infant death syndrome (SIDS) mortality across neighbourhood income quintiles among live births in Canada from 1991 through 2005.

METHODS

The Canadian linked live birth and infant death file was used, excluding births from Ontario, Yukon, Northwest Territories and Nunavut. Mortality rates for neonatal, postneonatal and sudden infant death syndrome (SIDS) were calculated by neighbourhood income quintile and period (1991-1995, 1996-2000, 2001-2005). Hazard ratios (HR) for neighbourhood income quintile and period were computed, adjusting for province of residence, maternal age, parity, infant sex and multiple birth.

RESULTS

In urban areas, for the entire study period (1991-2005), the poorest neighbourhood income quintile had a higher hazard of neonatal death (adjusted HR 1.24, 95% CI 1.15-1.34), postneonatal death (adjusted HR 1.58, 95% CI 1.41-1.76) and SIDS (adjusted HR 1.83, 95% CI 1.49-2.26) compared to the richest quintile. Postneonatal and SIDS mortality rates declined by 37% and 57%, respectively, between 1991-1995 and 2001-2005 whereas no significant change was observed in neonatal mortality. The decrease in postneonatal and SIDS mortality rates occurred across all income quintiles.

CONCLUSION

This study shows that despite a decrease in infant mortality and SIDS across all neighbourhood income quintiles over time in Canada, socio-economic inequalities persist. This finding highlights the need for effective infant health promotion strategies in vulnerable populations.