Risk Factors for Infant Mortality Edmond Shenassa, Sc.D ... · timeline, we recognize that this may not capture all possible articles in the published literature. ... then screened

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Risk Factors for Infant Mortality Edmond Shenassa, Sc.D., MA

Dane De Silva, MPH

Department of Family Science School of Public Health University of Maryland

April 1, 2019

DRAFT

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The following review has been completed for the Maryland Health Care Commission (MHCC),

pursuant to legislation (2018 Md. Laws, Chap. 83), requiring the Commission to conduct a

literature review to find appropriate national data on “factors, beyond the known factors of low

birth weight, teen pregnancy, poor nutrition, and lack of prenatal care, affecting the mortality of

African American infants and infants in rural areas in the United States and in the State” (2018

Md. Laws, Chap. 83, §1(b)(1)). This work will complement work being done by MHCC and

Maryland Department of Health staff on state data related to infant mortality. This literature and

the data analytics findings will be incorporated in the final report.

INTRODUCTION

In 2017, Maryland’s infant mortality rate of 6.4 per 1,000 births ranked 33rd among US states.

Since 2014, Maryland’s infant mortality rate (IMR) has remained fairly stable and about one

percentage point above the national average. This IMR translated to 1,908 preventable deaths

between 2014 and 2017. Maryland remains short of Healthy People 2020 benchmark rate of 6.4

deaths per 1,000 live births. This burden of infant mortality is borne disproportionately by people

of color. In particular, non-Hispanic black infants have the highest risk of death during the first

year of life. In the US, infant mortality rates for non-Hispanic black infants have remained 2.3

times higher than the risk for non-Hispanic white infants. While this racial disparity in IMR is

somewhat less pronounced in Maryland, the IMR among infants born to non-Hispanic black

women in Maryland (10.5) remains over twice larger than IMR among infants born to non-

Hispanic white women residing in the state. Moreover, this disparity in the risk of mortality

between black and white infants has increased recently as black infants are yet to experience the

declines in infant mortality rates that have been observed among white infants over the last

decade. According to the Maryland Department of Health, the infant mortality rate increased by

7% between 2016 and 2017 among black infants. Moreover, while the absolute burden of IMR is

highest in urban counties in Maryland, data from 2016 reveals a higher IMR among black infants

born in rural Maryland. Overall, the high risk of infant mortality, particularly among African

Americans remains a pressing public health concern in Maryland.

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On behest of Maryland Health Care Commission, we have conducted a systematic scoping

review of the literature on risk factors for IMR, with an emphasis beyond the known factors of

low birthweight, teen pregnancy, poor nutrition, and lack of prenatal care, affecting the mortality

of African American infants and infants in rural areas in the United States and in the State.

Recognizing the similarities and overlap between risk factors of the known causes of infant

mortality (birth defects, preterm birth, pregnancy complications, sudden infant death syndrome,

injuries)1 and the more down-stream risk factors, this review also includes a discussion of the

risk factors for the known causes.

Following the Preferred Reporting Items for Systematic Reviews and Meta-Analysis (PRISMA)

guidelines,2 this review was informed by the eco-social model (Figure 1). This model was

adapted from the social science by social epidemiologists in recognition of the dynamic

interrelations among various personal and environmental factors that drive most non-infectious

health outcomes.3 The utility of this ecologic approach is further underscored when we consider

that as much as 40% of poor maternal and child health (MCH) outcome occur among people

with no identifiable risk factors. Application of the social-ecological model in the last two

decades to a hoist of MCH issues, including infant mortality, has proven to have been quite

fruitful in explicating the structural determinants of maternal and child health. The structural

determinants of health, also referred to as underlying causes of disease, refer to the social and

economic conditions that influence individuals access to health promoting resources in one's

living and working conditions (e.g., distribution of income, wealth, influence, and power). As

such, the initial focus is on sociologic factors rather than individual-level risk behavior or genetic

predispositions. Below we review this evidence, first focusing on structural determinants of

health and then on its mediators.

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Figure 1 ‐ Eco‐social model of health

METHODS

Scoping review criteria

This scoping literature review followed a systematic approach to identify risk factors of infant

mortality or its causes (e.g., preterm birth, low birthweight, sudden infant death syndrome, safe

sleep) among our population of interest of African American women and rural women.

Specifically, we focused on ecologic and policy-level risk factors narrowing down to individual-

level risk factors of infant mortality within African American and rural populations. In

consultation with the University of Maryland’s Public Health librarian, and informed by

PRISMA guidelines, we developed a process for identifying, selecting, and reviewing articles.

Search terms and selection strategy

We searched PubMed and Embase from January 1, 2008 to December 31, 2018, using

combinations of Medical Subject Heading (MeSH) terms and subject headings to identify articles

and systematic reviews on risk factors for infant mortality. Given the project’s scope and

timeline, we recognize that this may not capture all possible articles in the published literature.

The following search terms were used in consultation with the authors of the complementary

review on programmatic interventions to prevent infant mortality: “population, rural”,

“communities, rural”, “African Americans”, “black*”, “risk”, “risk factor”, “characteristics,

social”, “determinant, mortality”, “social determinants of health”, “health disparit*”, “social

determinant*”, “infant mortality”, and “infant death”. Studies yielded from the searches were

then screened by titles to exclude any non-English and non-U.S. based studies. Duplicates were

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further excluded and the remaining studies were included for abstract review in the secondary

stage of screening.

Abstracts were independently screened by two reviewers (Co-I: Dane A De Silva, RA: Anne-

Olive Nono), using Rayyan (rayyan.qcri.com), a web-based application specifically developed to

facilitate systematic reviews. During abstract review, studies included by both reviewers were

advanced to full-text review, while studies with discordant results were resolved by consensus or

by reviewing the full-text review together. If consensus was still not reached, differences were

resolved by the PI (Edmond D Shenassa). Studies were excluded if infant mortality was not the

outcome or its known causes, were focused on maternal and infant medical conditions, or were

case studies. As we were specifically interested in the risk factors among African American and

rural populations, we also excluded studies that explored race as an exposure or covariate.

Descriptive studies that only reported on infant mortality rates were also not included.

Data extraction

The included list of studies went on to full-text review, where information on study aspects were

extracted by one of three reviewers (Co-I: Dane A De Silva, RA: Anne-Olive Nono, Arrey

Takor). Relevant study aspects were scrutinized for study design, population, comparison

groups, sample size, measurement of exposure(s) and outcome(s), and main findings (including

summary measures, such as odds ratios and relative risks). Any studies that were deemed not

relevant in the full-text review were excluded. Weekly meetings were convened to go over the

extraction process to ensure agreement.

RESULTS AND SUMMARY OF RISK FACTORS

Our search from PubMed and Embase resulted in 322 articles that were included for abstract

review after initial screen of title for non-US studies and removal of duplicates. Independent

abstract review resulted in a 64 articles being included for full-text review and abstraction. Upon

abstraction a further 24 studies were excluded, resulting in a total of 40 articles extracted for this

review (Figure 2).

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Table 1 presents a summary of empirical studies and meta-analyses organized according to

various levels of risk factors. A summary of these risk factors of infant mortality are presented

below by level starting with the ecologic level and concluding with individual-level risks. These

articles were specific to the African American population whereby studies presented race-

stratified results (unless otherwise specified). There were few studies on rural populations

captured in our search. Many of these studies used large population-based datasets that were

weighted to be representative of the national population. Where appropriate, we reported on

Figure 2. Schematic of studies included in the systematic review of risk factors of infant mortality.

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adjusted odds ratios, relative risks, or beta coefficients unless otherwise specified. Review

articles and qualitative studies are not included in the table but are summarized in the text below

in support of certain risk factors.

a. Ecologic/Policy-level

Income inequality

Income inequality is a key structural feature of communities and has been identified as a robust

determinant of health. In fact, it has been persuasively argued that the evidence linking income

inequality and poor health meets epidemiologic criteria for causality. This notion is further

supported by experimental evidence that health outcomes can be improved through manipulation

of levels of income inequality in communities.

In one study among 44 states (with IMR > 10) and the District of Columbia (DC), IMR (2007-

2009) was positively associated with state Gini level and state poverty level (R=0.397, p=.004

and R=0.543 p<.001, respectively).4 In stratified analyses, the association of the state Gini

coefficient with IMR became statistically non-significant.4 In the case of White IMR, although

the association with Gini was not significant, the pattern of association remained similar to that

of overall IMR versus Gini.4 This was not the case with Black IMR which was not correlated

with the Gini.4

Another study among 43 US states (with IMR > 10) reverse association between income

inequality and IMR (1992-2007) was observed.5 In this study’s follow-up, race-specific analysis

found a reverse association between income inequality and white IMR but no association

between income inequality and black IMR. Further analyses revealed a significant two-year

lagged negative effect of income inequality (particularly for blacks), with higher income

inequality associated with lower racial white IMR.6 In a further mixed-methods study on the

black infant mortality rate, increased racial income inequality was associated with an increased

black infant mortality rate.7

Racial Segregation

Several studies in our search looked at racial segregation in relation to the infant mortality rate or

preterm birth, including a meta-analysis and a systematic review.8–12 In one study among black

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infants (N=677,777) residing in 64 cities with a population of at least 250,000 residents (2000–

2002), the extent to which blacks were surrounded by other blacks was associated with elevated

infant mortality.8 High segregation, as measured by the Isolation index (dichotomized at .6), was

associated with a statistically insignificant 1.12 excess IMR and a statistically among black

infants. Segregation did not predict excess neo-natal deaths either.

Another study found that abolition of Jim Crow laws was followed by marked improvement in

several health indicators among African Americans, including infant mortality.9 However, Jim

Crow laws that espoused legal segregation in the South are distinct from the equally insidious

mechanisms that maintain a segregated society today.9 Findings from this paper do not readily

generalize beyond its time and place.

One study looking at black-white segregation as measured by either Theil’s Entropy Index, a

measure of evenness within a census tract, or xPx measures of isolation (the probability of two

randomly chosen people within a census tract being of the same race) in order to explain

variations in preterm birth rates less than 32 weeks.10 Areas with a higher isolation score was

associated with an increased rate of preterm birth <32 weeks, while areas with increased

evenness was associated with a decreased rate of preterm birth rate <32 weeks.10

In a meta-analysis, forty-two studies examined associations between segregation and adverse

birth outcomes among Black and White mothers separately. Meta-analyses revealed that among

Black mothers, segregation, as measured by either evenness, clustering, concentration,

centralization, or racial composition, was associated with increased risk of preterm birth, and low

birth weight.11 Black racial composition was associated with increased risk of preterm birth,

among those living in most- compared to least-segregated neighborhoods.11 Few studies were

conducted among White mothers and only exposure was associated with increased risk of

preterm birth and low birth weight.

Structural Racism

In our search, two studies looked at structural racism in relation to infant mortality. In one

specific study among the 50 US states, structural racism was measured by the ratio of black to

white population values in various domains of: prison incarceration and juvenile custody rates;

educational attainment; unemployment; prevalence of managerial positions; and median

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household income. In stratified analysis among African Americans, only unemployment within

the state's black population was positively associated with black infant mortality.13 None of the

structural racism measures were significantly associated with infant mortality among whites.

Another study among the 50 US states (1990-2004) found that state-level unemployment rates

depended on the time period.14 Among blacks, an increase in state unemployment rate was

associated with a decline in infant mortality, though this relationship weakened over time.14 This

relationship was not observed among whites. Authors posit that this decline in infant mortality

when unemployment rates rise is driven by declines of deaths due to preterm birth and low

birthweight.

State-level Medicaid spending

Two studies explored state-level Medicaid spending in relation to the infant mortality rate or

infant deaths due to congenital anomalies.15,16 Among 34 US states, funding of State Offices of

Minority Health (OMH) was associated with a decrease in Black IMR (1980–2007)

independently of other political and policy variables. The association between funding of OMH

is more pronounced during times of relatively lower Medicaid funding.15 Among the 50 US

states, states lacking Medicaid funding for pregnancy termination of fetuses with congenital

anomalies experience higher IMR attributed to congenital anomalies (2003-2007) relative to

states with such funding.16 This difference is most pronounced among black women on

Medicaid.16 Authors posit that lack of Medicaid funding for termination of anomalous fetuses

may be contributing to the black–white disparity in anomaly-related infant death.16

b. Community-level

Access to healthy food

Only one mixed-methods study looked at access to healthy foods in relation to the black infant

mortality rate among 100 MSAs in the US. They found that limited access to healthy foods,

defined as living in proximity to a grocery store, was associated with an increased infant

mortality rate.7

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County-level racism

One study looked at county-level racism in relation to preterm birth and low birthweight, two

leading causes of infant mortality. Both explicit and implicit prejudice were found to be

associated with an increased risk of preterm birth and low birthweight.17

Ethnic density of neighborhood

Another aspect of racial segregation is density of people from the same ethnic group. It is

proposed that a dense ethnic group provides advantages of shared culture, social networks, and

social capital that can be protective of health outcomes, including IMR, despite such areas

tending to be more socioeconomically deprived. This theory is based on consistent observations

of Hispanic paradox. Among black (N=581,151, living across 2,215 counties) mother-infant

dyads, levels of same-ethnic density were not associated with risk of infant mortality.18 In

contrast, higher density of Hispanics was associated with lower risk of infant mortality among

both Hispanic and black infants.19

Pollutants

Two studies looked at pollution in relation to infant mortality. One study explored possible

reasons for a 35% increase in black infant mortality after a nuclear plant became operational in

Port Gibson, Mississippi.20 This study is not relevant to Maryland residents. Another mixed-

methods study looked found an increased black infant mortality in areas with increased air

pollution.7

Rurality

Two studies looked at rurality in relation to neonatal mortality, postneonatal mortality, and

preterm birth <32 weeks among blacks. In one study, rural counties not next to a metropolitan

county was found to increase both neonatal and postneonatal mortality rates. This relationship

decreased when non-metropolitan counties were next to metropolitan counties with cities less

than 10,000 residents.21

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c. Organizational-level

Hospital characteristics

In our search, one study looked at hospital characteristics in relation to neonatal mortality due to

very low birthweight (<1500g) in New York City.22 Authors found that Black women delivered

in hospitals with higher mortality rates overall on average compared to non-Hispanic white

women. Hospitals with a high volume of very low birthweight infants with NICU capacities was

associated with a lower risk of neonatal mortality. Authors concluded that if African American

women delivered in hospitals with lower neonatal mortality rates (as non-Hispanic white

women), the disparity in infant mortality due to very low birthweight would decrease by

34.5%.22 Therefore, hospitals with high infant mortality may benefit from improved neonatal

care services to reduce infant mortality disparities.

d. Interpersonal-level

Inter-partner conflict/stress

Inter-partner stress was not examined in relation to infant mortality, but was examined in relation

to safe sleep practices. One study found that partner-associated stress in the previous 12 months

prior to delivery was associated with an increased risk of bed-sharing among African-American

women in WI.23 However, the reasons for this are not clearly understood, and authors did not

comment further. More research is warranted to ascertain the association between partner-

associated stress and safe sleep practices.

Paternal acknowledgement

Despite partner-associated stress, no paternal acknowledgement was found to have an increased

risk of infants not sleeping in supine position among African American women.24 Further studies

have also found that absent fathers have an increased risk of infant death, and its causes,

including preterm birth, low birthweight, compared to white women with fathers present.25,26

Consistent results were seen among teenage mothers specifically.27

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e. Individual-level factors

Assistance programs

Only one study found an association with use of assistance programs (WIC) and safe sleep

practices, specifically bed-sharing among African American women.28 Another review found

that receipt of welfare was associated with increased risk of preterm birth among African

American women.29 Further discussion and research about why assistance programs are

associated with increased bed-sharing or preterm birth is warranted.

Infant characteristics

The same study also found that an infant age <4 months was associated with an increased risk of

bed-sharing among African American women.28 This finding is important given the high risk of

infant mortality associated with this age range.

Marital status

Only one study reported on the association between marital status and infant mortality

(specifically due to preterm birth and low birthweight) among African American women.30 This

study reported an increased likelihood of infant mortality if a woman reported not being married.

Marital status may act as another proxy for paternal acknowledgement given its association with

infant mortality, as previously mentioned.

Maternal age

The risk of infant mortality follows a U-shaped association with maternal age, with an increased

risk among adolescent and older mothers.3 Three studies reported on associations with maternal

age in African-American women;23,30,31 however, results were dependent on the type of infant

mortality. One study reporting on infant mortality due to accidental suffocation and strangulation

found that maternal age <20 years was at an increased risk.31 Kitsantas et al. looked at infant

mortality due to congenital anomalies or preterm birth and low birthweight. They found that

African American mothers older than 35 years were at an increased risk of infant mortality due

to congenital mortality; however, mothers younger than 20 had a decreased risk of infant

mortality due to preterm birth.30 Other age categories were not found to be significant in their

sample. With regards to safe sleep practices, one study found maternal age (treated as a

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continuous variable) to be protective.23 In other words, there was a decreased risk of bed-sharing

with increasing maternal age.

Maternal & pregnancy health

Six studies highlighted the importance of maternal and pregnancy health on poor birth

outcomes.24,28,30,32–35 These include factors such as maternal morbidities and pregnancy

complications. One study examined depression during pregnancy or postpartum as a risk factor

of bed-sharing in African-American women in Florida.24 The authors found a strong risk

between maternal depression and bed-sharing. However, this result contrasts with another study,

which found a non-significant association with depressive symptoms.23

Other studies have also found associations between pregnancy history and complications and

infant death or stillbirth, such as having a previous small-for-gestational age infant or a previous

infant death or stillbirth.32–34 Complications such as hydramnios (excess amniotic fluid) and

oligohydramnios (too little amniotic fluid) was also associated with an increased risk of infant

mortality. 32

One study also examined previous birth outcomes of the mother as an infant, providing support

for the life course perspective, whereby birth outcomes are the product of the life course of the

mother and any early events that may have occurred, such as her own birth outcome. In this

study by Masho et al.,35 they found that if a mother was born preterm (<37 weeks) or low

birthweight (<2500g), they were at increased risk of having an infant death in their pregnancy.

These findings suggest that the full life course of the mother in addition to pregnancy and

postpartum health factors are important to reduce infant mortality.

Maternal education

Maternal education usually serves as a protective factor across races;3 however, among African

American women, education had no difference or carried an increased risk, and this was

dependent on the type of outcome. One study exploring accidental suffocation and strangulation

in bed found that all education levels were associated with an increased risk of the outcome

among African American women.31 Another study looking at postneonatal mortality found that

less than high school was associated with an increased risk.36 Lastly, one study found that having

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an education beyond high school carried an increased risk of bed-sharing among African

American women, although the reasons are unclear.23 Thus, depending on the type of outcome,

education may carry different risks among African Americans. These mixed findings also

suggest that there may be more factors beyond education that may be affecting this population.3

Maternal smoking

There is evidence that maternal smoking during pregnancy and in the infant’s environment is

associated with an increased risk of infant mortality.3 In our search, three studies examined

smoking in relation to infant mortality due to various reasons, and results were unequivocal and

consistent with the general body of knowledge.3,31,32,36

Maternal weight

Like age, maternal weight has been found to also have a U-shaped association with infant

mortality.3 In one review, findings were mixed. In general they found that women who were

overweight or obese were at increased risk of experiencing an infant death.3 However, they also

found one study that reported being underweight was associated with a decreased risk of infant

mortality.3 In our search, we found one study that treated pre-pregnancy BMI as a mediator to

explain the racial disparities among African Americans.37 They found that a BMI ≥ 30 kg/m2

explained 10% of the association between race and stillbirth or infant death. When looking at

severe obesity (BMI ≥ 35 kg/m2), it explained about 5% of the association.37

The review highlighted that this issue is complicated by gestational weight gain during

pregnancy.3 Women who do not gain an adequate amount of weight as per the Institute of

Medicine guidelines were at increased risk of death; however, excess pregnancy weight gain

appeared to have mixed results.3

Parity

Parity, or the number of times a woman has given birth, was indicated as a risk factor for infant

mortality, but the results were mixed and depended on the cause of infant mortality.30,31 One

study looking at accidental suffocation and strangulation in bed found that an African American

woman who has given birth to two ore more children was at an increased risk.31 Another study,

which looked at infant death due to congenital anomalies and preterm birth or low birthweight

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found differing results. For infant mortality due to congenital anomalies, parity did not appear to

be a significant risk factor.30 However, for infant mortality due to preterm birth or low

birthweight, African American women who had never given birth were at an increased risk of

infant mortality, whereas having given birth more than four times was at an non-significant

increased risk, likely due to a small sample size.30

Perhaps another related factor among parous women is the interpregnancy interval, or the

spacing between previous birth and the conception of the subsequent pregnancy.3 An

interpregnancy interval less than 18 months has been found to have an increased risk of neonatal

and postneonatal mortality.3 Such a finding emphasizes the importance of interpregnancy and

preconception health in meeting optimal birth spacing guidelines. However, factors such as

desirability and barriers to various forms of contraception remain important, particularly among

African American women.3

Pregnancy intention

Pregnancy intention was examined in relation to safe sleep practices. Only one study found an

association between pregnancy intention and the risk of bed-sharing.28 In that study, authors

found that African American women who got pregnancy later than intended were at increased

risk of bed-sharing than women who were pregnancy at the right time.28

Prenatal care

Receipt of adequate prenatal care has been known to have a lower risk of infant mortality.3,30,36,38

However, timing of when prenatal care is sought may also be important among African

Americans.24,31,32 One study found that seeking prenatal care in the second trimester or later was

associated with an increased risk of bed-sharing.24 Two other studies found that seeking no

prenatal care compared to having sought prenatal care in other trimesters was associated with an

increased risk of infant death.31,32 Qualitative studies among African American women have

indicated that structural barriers such as transportation and insurance, perceived poor quality of

care, and overt and covert racism from providers prevent them from seeking care.12,39,40

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Safe sleep

The importance of safe sleep has been important to prevent Sudden Infant Death Syndrome

(SIDS), as unsafe sleep practices is associated with an increased risk of SIDS. One study looked

at various infant sleep behaviors and risk factors among African American women.41 Authors

found bed-sharing, soft sleeping surfaces, bed sharing with smoking or previously smoking

mothers, bed-sharing without a pacifier, and bed-sharing among infants who were not breastfed

were at an increased risk of SIDS.41 Furthermore, qualitative studies have indicated that African

American women are skeptical about sleep position and SIDS, despite current recommendations

and interventions that promote infants sleeping in the supine position.3 Thus, there may be

specific cultural barriers that may not be addressed by current interventions among African

American women.

Other factors

One review found further risk factors that were not captured in our search. Breastfeeding for any

duration decreased the odds of SIDS.3 The authors also found two studies that found an increased

risk of death with non-prescription drug use.3 Furthermore, a change in employment status

between pregnancies was also found to increase the risk of infant death.3 It should be noted that

these factors were not necessarily among African American women only, but were relevant in its

association with infant death.

Conclusions

We conducted the above scoping literature review of literature that used national data to

investigate infant mortality of African American infants and infants in rural areas in the United

States and in the State for the Maryland Health Care Commission, pursuant to legislation (2018

Md. Laws, Chap. 83). We focused on risk factors “beyond the known factors of low birth weight,

teen pregnancy, poor nutrition, and lack of prenatal care.” In recognition of the overlap between

risk factors of the known causes of infant mortality as determined by the CDC (birth defects,

preterm birth, pregnancy complications, sudden infant death syndrome, injuries)1 and the other

risk factors, we also reviewed the literature on risk factors for the known causes. The social

ecologic model provided the framework for this review. We found 40 manuscripts in 24

categories across five levels.

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The majority of the literature focused on individual and interpersonal risk factors, the second

largest group of manuscripts focused on structural and community level factors, the literature on

organizational variables was relatively sparse and there was a dearth of literature examining

interactions across the five levels of influence. Practically all the literature focused on a few

variables and provided robust estimates for the effect of each of these chosen variables, but this

was achieved at the expense of accurately capturing the complexity of the syndrome of infant

mortality and the interactions between individual-level and social determinants that cause the

racial disparities in infant mortality in the US and the State.

In line with a vast body of literature from earlier decades, our review confirmed the continuing

relevance of classic individual-level factors that have been known for some time. The persistence

of disparities in infant mortality implicates etiologic factors beyond the individual and beyond

those that can be assessed during an office visit. In short, determining why infants die, does not

address why more black infants die than white infants. Thus, when considering individual-

level determinant of infant mortality among black populations in Maryland and beyond, we

would be wise to bear in mind that in the US well-educated and high-income black women do

not realize the same-level of protections against risk of infant mortality that is conferred to white

women with similar levels of education, income.e.g.,42 This phenomenon is perhaps most

pronounced in case of age where the u-shaped association between maternal age and pregnancy

outcomes, including infant mortality, that is observed among the general population, instead

approaches a linear association among black women.43 Another example regards income, white

women who transcend their parents’ low socio-economic status as adults, experience a

significant decrease in their risk of giving birth to a low birth weight baby but upwardly mobile

Black women do not realize the same reductions in risk.44 This focuses our attention on the

relatively sparse literature that highlights the importance of the lived experience of African

Americans both in terms of individual-level stressors and access to social resources that promote

health. An association between experience of racism and low birth weight is fairly well

established.45

At the structural level, we found race-specific association between IMR and protective effect of

income inequality among white Americans. These findings are in accord with an emerging body

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of work that suggest the health effects of some structural determinants of health, such as

income inequality, are race-specific in the US. This literature explains this counter intuitive

finding in terms of racial segregation of African Americans and persistent structural racism that

mediates the effects of income inequality by limiting access to health promoting resources.

Economic stratification related to income inequality often leads to concentration of poverty in

relatively small and well defined areas. These economically marginalized areas then experience

disinvestment in economic, social, educational, and physical resources that maintain and promote

health. Thus, the link between income inequality and health is mediated through access to health-

related resources. And it is noteworthy that evidence suggests that these structurally driven

disparities can become biologically encoded through subsequent generations.46 These

mechanisms operate perhaps more strongly among residents of rural areas; in particular, African

American residents of rural area.

This review should be considered in the context of its key imitation. Scoping reviews provide a

broad and accurate picture of the breadth of work conducted during a specified period of

timeframe but they do not allow for inclusion of seminal work outside of this timeframe and they

do not allow assess methodologic quality of the included studies.

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REFERENCES

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3. Reno R, Hyder A. The Evidence Base for Social Determinants of Health as Risk Factors for Infant Mortality: A Systematic Scoping Review. J Health Care Poor Underserved. 2018;29(4):1188-1208. doi:10.1353/hpu.2018.0091

4. Kershenbaum A, Price J, Nagle NN, Erwin PC. The pattern of association between U.S. economic indicators and infant mortality rates at the state level. J Health Care Poor Underserved. 2014;25(3):1432-1448. doi:10.1353/hpu.2014.0144

5. Siddiqi A, Jones MK, Erwin PC. Does higher income inequality adversely influence infant mortality rates? Reconciling descriptive patterns and recent research findings. Soc Sci Med. 2015;131:82-88. doi:10.1016/j.socscimed.2015.03.010

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7. Wallace ME, Green C, Richardson L, Theall K, Crear-Perry J. “Look at the Whole Me”: A Mixed-Methods Examination of Black Infant Mortality in the US through Women’s Lived Experiences and Community Context. Int J Environ Res Public Health. 2017;14(7). doi:10.3390/ijerph14070727

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17. Orchard J, Price J. County-level racial prejudice and the black-white gap in infant health outcomes. Soc Sci Med. 2017;181:191-198. doi:10.1016/j.socscimed.2017.03.036

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20. Mangano JJ. Excess infant mortality after nuclear plant startup in rural Mississippi. Int J Health Serv. 2008;38(2):277-291. doi:10.2190/HS.38.2.d

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22. Howell EA, Hebert P, Chatterjee S, Kleinman LC, Chassin MR. Black/white differences in very low birth weight neonatal mortality rates among New York City hospitals. Pediatrics. 2008;121(3):e407-415. doi:10.1542/peds.2007-0910

23. Salm Ward TC, Ngui EM. Factors Associated with Bed-Sharing for African American and White Mothers in Wisconsin. Matern Child Health J. 2015;19(4):720-732. doi:10.1007/s10995-014-1545-5

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25. Alio AP, Kornosky JL, Mbah AK, Marty PJ, Salihu HM. The impact of paternal involvement on feto-infant morbidity among Whites, Blacks and Hispanics. Matern Child Health J. 2010;14(5):735-741. doi:10.1007/s10995-009-0482-1

26. Alio AP, Mbah AK, Kornosky JL, Wathington D, Marty PJ, Salihu HM. Assessing the impact of paternal involvement on racial/ethnic disparities in infant mortality rates. J Community Health. 2011;36(1):63-68. doi:10.1007/s10900-010-9280-3

27. Alio AP, Mbah AK, Grunsten RA, Salihu HM. Teenage pregnancy and the influence of paternal involvement on fetal outcomes. J Pediatr Adolesc Gynecol. 2011;24(6):404-409. doi:10.1016/j.jpag.2011.07.002

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29. Lorch SA, Enlow E. The role of social determinants in explaining racial/ethnic disparities in perinatal outcomes. Pediatr Res. 2016;79(1-2):141-147. doi:10.1038/pr.2015.199

30. Kitsantas P. Ethnic differences in infant mortality by cause of death. J Perinatol. 2008;28(8):573-579. doi:10.1038/jp.2008.35

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32. Zhang L, Cox RG, Graham J, Johnson D. Association of maternal medical conditions and unfavorable birth outcomes: findings from the 1996-2003 Mississippi linked birth and death data. Matern Child Health J. 2011;15(7):910-920. doi:10.1007/s10995-009-0516-8

33. August E.M., Salihu H.M., Weldeselasse H., Biroscak B.J., Mbah A.K., Alio A.P. Infant mortality and subsequent risk of stillbirth: A retrospective cohort study. BJOG Int J Obstet Gynaecol. 2011;118(13):1636-1645. doi:10.1111/j.1471-0528.2011.03137.x

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35. Masho SW, Archer PW. Does maternal birth outcome differentially influence the occurrence of infant death among African Americans and European Americans? Matern Child Health J. 2011;15(8):1249-1256. doi:10.1007/s10995-010-0704-6

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38. Cox R.G., Zhang L., Zotti M.E., Graham J. Prenatal Care Utilization in Mississippi: Racial Disparities and Implications for Unfavorable Birth Outcomes. Matern Child Health J. 2009;((Cox) Department of Microbiology and Immunology, Vanderbilt University School of Medicine, C2213 Medical Center North, 1161 21st Ave S, Nashville, 37232-2581, United States):1-12. doi:10.1007/s10995-009-0542-6

39. Mazul MC, Salm Ward TC, Ngui EM. Anatomy of Good Prenatal Care: Perspectives of Low Income African-American Women on Barriers and Facilitators to Prenatal Care. J Racial Ethn Health Disparities. 2017;4(1):79-86. doi:10.1007/s40615-015-0204-x

40. Barnes GL. Perspectives of African-American women on infant mortality. Soc Work Health Care. 2008;47(3):293-305. doi:10.1080/00981380801985457

41. Fu LY, Moon RY, Hauck FR. Bed sharing among black infants and sudden infant death syndrome: interactions with other known risk factors. Acad Pediatr. 2010;10(6):376-382. doi:10.1016/j.acap.2010.09.001

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Table 1. Data abstraction table of risk factors of infant mortality or its antecedents, stratified by level of organization Risk factor Reference Sample

Size Study Setting

Study Period

Type of study/design

DV IV Effect (95% confidence interval or p‐value)

Ecologic/Policy‐level Markers of population health

Wallace 2017 100 MSAs

US 2010‐2013

Mixed‐Methods

Infant mortality rate Smoking prevalence among adults aRR 1.20 (1.13, 1.27)

Obesity prevalence among adults aRR 1.16 (1.10, 1.22)

Medicaid spending Patton D 2014 918 34 states

1980‐2007

Quasi‐experimental

Infant mortality rate

Medicaid spending b= ‐3.3 (p<0.01)

Hutcheon 2014 11.5 million

US 1983‐2004

Ecologic Infant deaths due to congenital anomalies

No state Medicaid funding for pregnancy termination (1983)

aOR 1.01 (0.96, 1.06)

No state Medicaid funding for pregnancy termination (2004)

aOR 1.23 (1.17, 1.30)

No state Medicaid funding for pregnancy termination (Black women on Medicaid)

aOR 1.94 (1.52, 2.36)

Presence of Office of Minority Health

Patton D 2014 918 34 states

1980‐2007


Infant mortality rate Presence of OMH b= ‐0.75 (p<0.05)

State educational attainment

Wallace M 2017

NS US 2010‐2013

Ecologic Infant death Black educational attainment aRR 0.85 (0.78, 0.93)

Ratio of Black to white educational attainment

aRR 0.92 (0.85, 0.99)

State imprisonment rate

Wallace M 2017

NS US 2010‐2013

Ecologic Infant death Prison incarceration rate aRR 1.06 (0.96, 1.16)

Black imprisonment rate aRR 1.02 (0.96, 1.08)

State managerial position

Wallace M 2017

NS US 2010‐2013

Ecologic Infant death Higher levels of managerial employment aRR 0.91 (0.85, 0.99)

State median household

Wallace M 2017

NS US 2010‐2013

Ecologic Infant death Black median aRR 0.86 (0.77, 0.98)

State poverty Kershenbaum 2014

NS US 2007‐2009

Ecologic Overall infant mortality

Income inequality (Gini coefficient) R = 0.397 (p=0.004)

Black Infant mortality

Income inequality (Gini coefficient) R = 0.152 (p=0.324) State black poverty level R = 0.360 (p=0.018)

Siddiqi 2016 NS 43 states

1992‐2007

Ecologic Infant mortality rate Income inequality (Gini coefficient) b= ‐0.100 (p=0.155) Lagged income inequality by 2 years (Gini coefficient)

b= ‐0.131 (p=0.043)


US 2010‐2013

Mixed‐Methods

Infant mortality rate Racial income inequality aRR 1.08 (1.01, 1.16)

State racial discrimination

Krieger 2013 NS US 1965‐2004

Ecologic Infant death Jim Crow polity states (by cohort)

1965‐1969 aRR 0.89 (0.79, 1.00)

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2000‐2004 aRR 1.21 (1.07, 1.36)

State unemployment Wallace M 2017

NS US 2010‐2013

Ecologic Infant death Black unemployment aRR 1.06 (1.00, 1.12)

Ratio of black to white unemployment aRR 1.05 (1.01, 1.10)

Orsini 2015 NS US 1980‐2004

Ecologic Infant mortality rate Unemployment by cohort

1980‐1989 b= ‐1.8701 (p<0.01)

1990‐2004 b= ‐0.6960 (p>0.10)

1980‐2004 b= ‐1.6336 (p<0.05)

Community‐level Access to healthy foods


US 2010‐2013

Mixed‐Methods

Infant mortality rate Limited access to healthy foods aRR 1.09 (1.01, 1.19)

County‐level racism Orchard 2017 31.5 million

US 2002‐2012

Ecologic Preterm birth Explicit prejudice b=9.36 (p<0.01)

Preterm birth Implicit prejudice b=7.81 (p<0.01)

Low birthweight Explicit prejudice b=6.04 (p<0.01)

Low birthweight Implicit prejudice b=4.94 (p<0.01)

Ethnic density of neighborhood

Shaw RJ 2013 581,151 US 2000 Cross‐sectional/ Ecologic

Infant death Hispanic density of neighborhood

1‐4.99% aOR 0.96 (0.88, 1.03)

5‐14.99% aOR 0.86 (0.77, 0.96)

15‐49.9% aOR 0.66 (0.55, 0.79)

≥50% aOR 1.09 (0.34, 3.55)

Shaw RJ 2010 581,151 US 2000 Cross‐sectional/ Ecologic

Infant death Same ethnic density of county

1‐4.99% aOR 1.03 (0.67, 1.57)

5‐14.99% aOR 1.14 (0.76, 1.72)

15‐49.9% aOR 1.18 (0.79, 1.78)

≥50% aOR 1.18 (0.77, 1.79)

Pollutants Mangano JJ 2008

5 counties

MS, LA 1981‐1984


Infant mortality Proximity to nuclear plant (overall) SMR 1.45 (1.11, 1.79)

Proximity to nuclear plant (Blacks) SMR 1.35 (0.35, 1.75)


US 2010‐2013

Mixed‐methods

Infant mortality Air pollution aRR 1.11 (1.03, 1.19)

Rurality Sparks 2009 2,934 counties

US 1998‐2002

Ecologic Neonatal mortality Rurality (not next to a metropolitan county, no town of 2,500 residents)

b=0.742 (p<0.01)

Non‐metropolitan county (next to large metropolitan county, no city with 10,000 residents)

b=0.649 (p<0.05)

Non‐metropolitan county (next to small metropolitan county, contains city with 10,000 residents)

b=0.653 (p<0.001)

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Non‐metropolitan county (next to metropolitan county, no city with 10,000 residents)

b=0.384 (p<0.01)

Postneonatal mortality

Rurality (not next to a metropolitan county, no town of 2,500 residents)

b=1.31 (p<0.001)

Non‐metropolitan county (next to large metropolitan county, no city with 10,000 residents)

b=0.397 (p<0.01)

Non‐metropolitan county (next to small metropolitan county, contains city with 10,000 residents)

b=0.319 (p<0.001)

Non‐metropolitan county (next to metropolitan county, no city with 10,000 residents)

b=0.613 (p<0.001)

Kramer 2008 311 MSAs

US 2002‐2004

Ecologic Preterm birth <32 weeks

Metropolitan area R2 = 0.26

Segregation Hearst 2008 677,777 US 2000‐2002

Ecologic Infant death Segregation (isolation index) RD 1.12 (‐0.51, 2.74)

Kramer 2008 311 MSAs

US 2002‐2004

Ecologic Preterm birth <32 weeks

Theil's index

Isolation b= 2.7 (p<0.01)

Evenness b= ‐2.0 (p<0.05)


US 2010‐2013

Mixed‐methods

Infant mortality Residential segregation (isolation) aRR 1.10 (1.05, 1.15)

Mehra 2017 42 articles

US articles to 2017

Meta‐analysis Preterm birth Segregation OR 1.17 (1.10, 1.26)

Low birthweight Segregation OR 1.13 (1.06, 1.21)

Preterm birth Black racial composition OR 1.20 (1.05, 1.37)

Organizational‐level Hospital characteristics

Howell 2008 11,781 NYC 1996‐2001

Retrospective cohort

Overall neonatal mortality due to very low birthweight

Hospitals with high volume of VLBW aOR 0.77 (0.60, 1.00)

Interpersonal‐level Inter‐partner conflict/stress

Salm Ward TC, 2015

806 WI 2007‐2010

Cross‐sectional

Bed‐sharing Partner‐associated stress in the 12 months prior to delivery

aOR 1.79 (1.22, 2.63)

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Paternal acknowledgement

Broussard 2012 1344 FL 2004‐2005

Cross‐sectional

Infrequent back‐sleeping

No paternal acknowledgement aOR 2.13 (1.52, 2.97)

Alio 2010 1.4 million

FL 1998‐2005

Cross‐sectional

Very low birthweight (<1500 g)

Father absent aOR 4.85 (4.56, 5.15)

Low birthweight (<2500)


Preterm birth (<37 wks)


Very preterm birth (<33 wks)


Small for gestational age


Alio 2010 1.4 million

FL 1998‐2005

Cross‐sectional

Infant death Father absent aOR 6.74 (6.22, 7.31)

Father present aOR 2.02 (1.89, 2.16)

Individual‐level Assistance programs

Salm Ward TC 2016

3,528 GA 2004‐2011

Cross‐sectional

Safe sleep (Bed‐sharing)

WIC aOR 1.6 (1.11, 2.3)

Infant characteristics

Salm Ward TC 2016

3,528 GA 2004‐2011

Cross‐sectional


Age <4 months aOR 2.4 (1.6, 3.7)

Marital status Kisantas 2008 234,535 NC 1989‐1997

Cross‐sectional

Infant mortality due to preterm birth/low birthweight

Not married aOR 1.34 (1.22, 1.61)

Maternal age

Salm Ward TC 2015

806 WI 2007‐2010

Cross‐sectional


Maternal age aOR 0.96 (0.93, 0.99)

Carlberg MM 2012

1,7 million

US 2000‐2002

Cross‐sectional

Accidental suffocation/strangulation in Bed (ASSB)

Maternal age <20 aOR 2.12 (1.42, 3.16)

Kisantas 2008 234,535 NC 1989‐1997

Cross‐sectional

Infant mortality due to congenital anomalies

Maternal age ≥35 aOR 1.65 (1.21, 2.27)

Kisantas 2008 234,535 NC 1989‐1997

Cross‐sectional


Maternal age <20 aOR 0.78 (0.65, 0.93)

Maternal & pregnancy health

Zhang 2011 141,426 MS 1996‐2003

Cross‐sectional

Infant death Hydramnios/Oligohydramnios aOR 5.6 (4.0, 7.7)

Zhang 2011 141,426 MS 1996‐2003

Cross‐sectional

Infant death Previous small infant aOR 2.9 (2.2, 3.8)

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August EM, 2011

44,871 MO 1989‐2005


Stillbirth Previous infant death aHR 4.28 (2.61, 6.99)

Salihu MH 2011 45,398 MO 1989‐2005


Infant death Previous stillbirth aHR 2.68 (1.41, 5.09)

Kitsantas 2008 234,535 NC 1989‐1997

Cross‐sectional

Infant death due to congenital anomalies

Previous infant death aOR 2.19 (1.43, 3.35)

Broussard 2012 1344 FL 2004‐2005

Cross‐sectional


Depression during pregnancy or postpartum aOR 7.50 (4.16, 13.53)

Salm Ward TC 2016

3,528 GA 2004‐2011

Cross‐sectional


Depressive symptoms aOR 1.05 (0.70, 1.57)

Masho 2011 742 VA 1997‐2007

Case‐Control Infant death Mother born preterm (<37 wks) aOR 2.81 (1.22, 6.48)

Mother born low birthweight (<2500g)

aOR 2.91 (1.19, 7.11)

Maternal education Salm Ward TC, 2015

806 WI 2007‐2010

Cross‐sectional


Education >13 years aOR 1.90 (1.16, 3.42)

Carlberg MM 2012

1.7 million

US 2000‐2002

Cross‐sectional


Education

<12 years aOR 2.99 (1.52, 5.84)

High School aOR 2.26 (1.17, 4.37)

Less than college aOR 2.08 (1.05, 4.11)

Kitsantas 2010 264,268 NC 1999‐2007

Cross‐sectional


Education <9 years

<9 years aOR 1.86 (1.26, 2.77)

9‐11 aOR 1.38 (1.14, 1.68)

Maternal smoking Carlberg MM 1.7 million

US 2000‐2002

Cross‐sectional


Any smoking aOR 2.63 (2.04, 3.39)

Zhang 2011 141,426 MS 1996‐2003

Cross‐sectional

Infant death Heavy smoking (≥10 cig/day) aOR 1.6 (1.3, 1.9)

Kitsantas 2010 264,268 NC 1999‐2007

Cross‐sectional


Any smoking aOR 1.65 (1.39, 1.94)

Maternal weight Lemon 2016 179,939 PA 2006‐2011

Cross‐sectional

Stillbirth Obesity (≥30 kg/m2) 10.6% explained (mediation)*

Infant death Obesity (≥30 kg/m2) 9.8% explained

Stillbirth Severe Obesity (≥35 kg/m2) 4.7% explained

Infant death Severe Obesity (≥35 kg/m2) 5.9% explained

Parity Carlberg MM US Parity

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1.7 million

2000‐2002

Cross‐sectional


2 aOR 1.96 (1.42, 2.72)

3 aOR 2.72 (1.89, 3.94)

4+ aOR 4.43 (3.03, 6.50)

Kisantas 2008 234,535 NC 1989‐1997

Cross‐sectional


Nulliparous aOR 0.98 (0.80, 1.22)

4+ aOR 1.44 (0.97, 2.12)


Nulliparous aOR 1.47 (1.30, 1.67)

4+ aOR 1.45 (0.97, 2.17)

Pregnancy intention

Salm Ward TC 2016

3,528 GA 2004‐2011

Cross‐sectional


Later than intended aOR 2.2 (1.4, 3.5)

Prenatal care Broussard 2012 1344 FL 2004‐2005

Cross‐sectional


Prenatal care (2nd trimester or later) aOR 3.78 (2.24, 6.39)

Carlberg MM 1.7 million

US 2000‐2002

Cross‐sectional


Timing of prenatal care: none aOR 1.70 (1.08, 2.68)

Zhang 2011 141,426 MS 1996‐2003

Cross‐sectional

Infant death Timing of prenatal care: none aOR 3.3 (2.6,4.2)

Cox 2009 300,710 MS 1996‐2003

Retrospective Cohort

Infant mortality Intensive prenatal care aOR 2.1 (1.9‐2.3)

Intermediate prenatal care aOR 1.3 (1.1‐1.5)

Inadequate prenatal care aOR 1.5 (1.3‐1.7)

No prenatal care aOR 5.4 (4.2, 7.0)

Kitsantas 2010 264,268 NC 1999‐2007

Cross‐sectional

Neonatal mortality Inadequate prenatal care aOR 1.35 (1.17, 1.56)

Kisantas 2008 234,535 NC 1989‐1997

Cross‐sectional


Inadequate prenatal care aOR 1.23 (1.10, 1.49)

Safe Sleep Fu 2010 390 IL (Chicago)

1993‐1996

Case‐Control SIDS Bed sharing aOR 2.0 (1.2, 3.4)

Bed sharing while using a pillow aOR 4.1 (1.4, 11.5)

Soft sleep surface aOR 8.8 (3.5, 21.7)

Bed sharing with smoking mothers aOR 6.0 (2.7, 13.4)

Bed sharing with previous smoking mothers aOR 8.0 (3.4, 18.5)

Bed sharing with infants <1 month aOR 7.1 (1.2, 42.1

Bed sharing without a pacifier aOR 2.1 (1.1, 3.9)

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Bed sharing among infants who were not breastfed

aOR 1.9 (1.1, 3.4)

aOR (adjusted odds ratio), aHR (adjusted hazard ratio), aRR (adjusted relative risk), b (beta coefficient), MSA (metropolitan statistical areas), NS (not specified), RD (risk difference), SMR (standard mortality rate), SIDS (sudden infant death syndrome), WIC (Special Supplemental Nutrition Program for Women, Infants, and Children) *p‐values not presented

Risk Factors for Infant Mortality Edmond Shenassa, Sc.D ... · timeline, we recognize that this may not capture all possible articles in the published literature. ... then screened

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