Infant Mortality

Infant mortality refers to the death of a child before reaching their first birthday, with the infant mortality rate (IMR) being a key demographic indicator measuring the number of such deaths per 1,000 live births in a given year [7]. It is a critical measure of population health and the effectiveness of a society's healthcare system, often serving as a sensitive marker for broader socioeconomic conditions, public health practices, and medical care quality [7]. The concept is closely related to under-5 mortality, which tracks deaths of children under five years of age, with extensive global data compiled by entities like the UN Inter-agency Group for Child Mortality Estimation (UN IGME) [3]. A significant portion of child deaths occurs in the neonatal period—the first 28 days of life—which represents one of the most vulnerable phases of human development [2]. The measurement and analysis of infant mortality involve several classifications, with neonatal mortality (death within the first 28 days) and postneonatal mortality (death from 28 days to one year) being primary distinctions. Causes are multifactorial, spanning biological, environmental, and social determinants. Research, such as multilevel analyses of demographic health surveys, examines factors at individual, household, and community levels that contribute to infant death risks, including maternal health, birth conditions, access to care, and socioeconomic status [5]. Disparities in infant mortality rates, both within and between countries, reveal persistent inequalities that cannot be explained by genetic factors alone, pointing to systemic issues in healthcare access and social equity [6]. The collection of accurate data is essential, though challenges like undercounting require methodological corrections to understand true global burdens [1]. Globally, trends in infant and under-5 mortality are monitored to assess progress toward international development goals, such as the historic Millennium Development Goals and subsequent Sustainable Development Goals established by the United Nations [1]. Despite significant declines over recent decades, nearly half of all under-5 deaths still occur in the newborn period, highlighting the need for intensified perinatal and newborn care [2]. Major disruptions like the COVID-19 pandemic have posed new risks, with emerging data from low- and middle-income countries indicating potential impacts on infant and neonatal health outcomes due to strained health systems, though the full effects are still being studied [4]. As a cornerstone metric of public health, infant mortality remains central to evaluating global health initiatives, informing policy, and targeting interventions to reduce preventable child deaths worldwide [3][7].

Overview

Infant mortality, defined as the death of a child before their first birthday, is a critical demographic and public health indicator. The infant mortality rate (IMR), typically expressed as the number of infant deaths per 1,000 live births in a given year, serves as a sensitive and widely used measure of a population's overall health and the quality of its healthcare system, social services, and economic conditions [13]. This metric is foundational to epidemiology and health policy, providing a quantifiable benchmark for comparing health outcomes across different regions, countries, and time periods. Its calculation is standardized, allowing for meaningful international comparisons, such as those compiled by organizations like the Kaiser Family Foundation, which track disparities between nations like the United States and its economic peers [14]. The IMR's sensitivity stems from infants' heightened vulnerability to a wide array of environmental, medical, and socioeconomic factors, making it an early warning signal for broader societal issues.

The Infant Mortality Rate as a Societal Barometer

The infant mortality rate functions as a powerful diagnostic tool for assessing the well-being of a society. A low IR is generally associated with advanced healthcare infrastructure, including accessible prenatal and postnatal care, widespread immunization programs, and effective treatment for childhood illnesses [13]. Conversely, elevated rates often point to systemic failures, including poverty, malnutrition, inadequate sanitation, limited access to medical services, and educational disparities. The rate is so integral to understanding population health that it is a cornerstone of demographic studies and a key component of the Human Development Index (HDI). International comparisons reveal stark disparities; for instance, data shows that the United States, despite its high per-capita healthcare expenditure, has a persistently higher IMR than many other developed nations, prompting analysis of underlying causes such as socioeconomic inequality and variations in healthcare access [14]. This comparative analysis is crucial for identifying best practices and formulating targeted public health interventions.

Global Initiatives and the Millennium Development Goals

The global recognition of infant mortality as a preventable tragedy catalyzed significant international action. This awareness was formally institutionalized with the establishment of the United Nations Millennium Development Goals (MDGs) in 2000. MDG 4 specifically aimed to reduce the under-five mortality rate by two-thirds between 1990 and 2015, with the IMR being a central component of this target. The MDG framework underscored the multi-dimensional nature of development, linking child survival directly to goals related to poverty eradication, maternal health, and combating infectious diseases. The promotion of these goals under the aegis of the United Nations mobilized unprecedented global resources and political commitment toward improving child health outcomes worldwide. The successor framework, the Sustainable Development Goals (SDGs), adopted in 2015, continues this focus through SDG Target 3.2, which aims to end preventable deaths of newborns and children under 5 years of age by 2030. These goals emphasize that reducing infant mortality requires integrated strategies beyond the healthcare sector alone, encompassing nutrition, education, gender equality, and infrastructure development.

The Critical Neonatal Period and Causes of Mortality

Building on the concept of vulnerability discussed earlier, the causes of infant mortality are often categorized by the timing of death. The neonatal period (the first 28 days of life) is distinct in its risk profile. As noted earlier, this period represents an exceptionally vulnerable phase. The major causes of neonatal mortality are predominantly related to conditions arising during pregnancy, delivery, or immediate adaptation to extra-uterine life. These include:

• Preterm birth complications (e.g., respiratory distress syndrome)
• Intrapartum-related events (birth asphyxia or trauma)
• Neonatal infections (such as sepsis, pneumonia, and tetanus)
• Congenital anomalies

In contrast, post-neonatal mortality (deaths from 28 days to one year) is more frequently associated with environmental and external factors, including:

• Infectious diseases (e.g., diarrhea, malaria, measles)
• Malnutrition and its sequelae
• Sudden Infant Death Syndrome (SIDS)
• Accidents (injuries)

The provision of quality intrapartum care—skilled attendance at birth, emergency obstetric care, and neonatal resuscitation—is therefore paramount to saving lives in the first month. This is followed by essential newborn care, including thermal protection, early and exclusive breastfeeding, infection prevention, and identification/treatment of sick newborns.

Measurement, Trends, and Disparities

Accurate measurement of infant mortality is complex and requires robust vital registration systems. The standard formula for calculating the Infant Mortality Rate (IMR) in a given year is: IMR = (Number of infant deaths / Number of live births) × 1,000

This rate can be further stratified into:

• Early neonatal mortality rate (deaths 0-6 days)
• Late neonatal mortality rate (deaths 7-27 days)
• Post-neonatal mortality rate (deaths 28-364 days)

Globally, significant progress has been made. The worldwide IMR fell from an estimated 65 deaths per 1,000 live births in 1990 to 29 in 2017 according to UN data. However, progress has been uneven, and vast disparities persist both between and within countries. Sub-Saharan Africa and Southern Asia continue to account for the vast majority of global infant deaths. Within nations, disparities often follow lines of socioeconomic status, race, ethnicity, geography (urban vs. rural), and parental education level. For example, in the United States, significant racial and ethnic disparities in IMR persist, with rates for non-Hispanic Black infants consistently more than double those for non-Hispanic White infants, highlighting the role of social determinants of health [14]. Monitoring these disparities is essential for equitable health policy and targeted intervention.

Strategies for Reduction and Prevention

Effective strategies to reduce infant mortality are multi-faceted and evidence-based. They operate across the continuum of care, from pre-pregnancy through the first year of life. Key interventions include:

• Preconception and prenatal care: Folic acid supplementation, management of chronic conditions, screening and treatment for infections, and nutritional support. - Quality intrapartum care: Skilled birth attendance, management of obstetric complications, and immediate newborn care (thermal protection, resuscitation if needed). - Postnatal and infant care: Promotion of exclusive breastfeeding, immunization according to the WHO schedule, safe sleep practices to prevent SIDS, and growth monitoring. - Public health measures: Improved sanitation and access to clean water, vector control to prevent malaria, and nutrition programs. - Social and policy interventions: Poverty reduction, female education, strengthening health systems, and universal health coverage to ensure access to services. The integration of these strategies into strong primary healthcare systems is recognized as the most effective approach to achieving sustainable reductions in infant mortality and improving child health outcomes globally.

History

Early Observations and Statistical Foundations

The systematic study of infant mortality as a demographic phenomenon began in earnest during the 19th century, coinciding with the development of modern vital statistics registration systems. Prior to this period, infant deaths were often subsumed within general mortality figures or recorded only anecdotally. The establishment of standardized birth and death registration in several European nations and the United States enabled the first reliable calculations of infant mortality rates (IMR), typically expressed as the number of deaths of children under one year of age per 1,000 live births in a given year. This quantification transformed infant mortality from a private tragedy into a measurable public health indicator, allowing for temporal and geographic comparisons. Early analyses quickly revealed stark disparities, not only between nations but also within them, linking high infant mortality to urban poverty, poor sanitation, and inadequate nutrition [16].

The 20th Century: Technological Advances and Persistent Disparities

The early to mid-20th century witnessed a dramatic decline in infant mortality in industrialized nations, a trend largely attributed to public health improvements rather than clinical medical advances. Key interventions included:

• Pasteurization of milk and improved infant nutrition
• Public sanitation projects and clean water supplies
• The development and widespread use of vaccines against diseases like diphtheria and pertussis
• Educational campaigns on hygiene and infant care

However, by the latter half of the century, the rate of decline slowed in many high-income countries, and the epidemiological profile of infant deaths shifted. As infectious disease burdens diminished, the proportion of deaths occurring in the neonatal period (first 28 days) and attributable to congenital conditions, prematurity, and complications of pregnancy and childbirth became more prominent [16]. This period also saw the refinement of statistical methodologies. For instance, researchers began employing frontier estimation techniques to recalculate rates and derive measures of likely undercount for each country, acknowledging that official statistics could be compromised by incomplete registration, particularly for early neonatal deaths [15].

The Late 20th and Early 21st Century: The International Benchmarking Era

From the 1970s onward, international comparisons of infant mortality became a standard tool for assessing national health system performance and socioeconomic development. A landmark 2010 analysis comparing the United States and European Union countries highlighted a persistent and puzzling gap: despite higher per capita health expenditure, the U.S. IMR remained elevated [16]. This study identified several contributing factors distinct from the clinical causes of death, including:

• A higher percentage of preterm births in the U.S. - Differences in the registration of "borderline" live births, where some European countries may have registered events with extremely low gestational age or birth weight as fetal deaths rather than live births, artificially lowering their IMR
• Socioeconomic disparities in access to care, which were more pronounced in the U.S. [16]

This comparative work underscored that a nation's aggregate IMR could mask significant internal inequalities. As noted in related research, policies focusing solely on improving health at birth, such as expanding prenatal care, would be incomplete without also addressing the broader social and economic determinants affecting less advantaged groups [15].

The Millennium Development Goals and a Renewed Global Focus

The turn of the 21st century marked a pivotal shift toward a coordinated global effort to reduce child mortality. MDG 4 specifically aimed to reduce the under-five mortality rate by two-thirds between 1990 and 2015. This framework elevated infant and child mortality as a paramount indicator of multidimensional development, linking it to goals concerning poverty, maternal health, and disease prevention. The MDG era spurred unprecedented data collection and monitoring efforts, revealing the severe and uneven global burden. Building on the geographical patterns mentioned previously, data confirmed that sub-Saharan Africa and Southern Asia accounted for the overwhelming majority of these deaths, focusing international aid and health policy on these regions.

Contemporary Understanding and the Sustainable Development Goals

Post-2015, the agenda transitioned to the Sustainable Development Goals (SDGs), with Target 3.2 aiming to end preventable deaths of newborns and children under 5 by 2030. Contemporary analysis, such as the 2022 global burden assessments, has intensified focus on the neonatal period. It was found that nearly half (47%) of all under-five deaths occurred in the first 28 days of life, emphasizing this phase as the most vulnerable and highlighting the critical need for quality intrapartum and immediate newborn care. This modern epidemiological profile demands interventions across the continuum of care, from pre-pregnancy through the first year, a strategy now central to global health frameworks. The historical trajectory of infant mortality reveals an evolution from a generalized measure of population health to a finely differentiated indicator requiring specific, life-stage-targeted interventions. The journey from rudimentary vital statistics to sophisticated international benchmarking and goal-setting reflects a growing understanding of its complex etiology, shaped by an interplay of biomedical, social, and economic factors that continue to define research and policy agendas today [15][16].

Description

Infant mortality, defined as the death of a child before their first birthday, serves as a fundamental indicator of population health and socioeconomic development [13][14]. The measurement of this metric, however, is complicated by significant challenges in data quality and completeness, particularly in regions with the highest burden. A critical methodological advancement in addressing this issue is the application of frontier estimation techniques with a one-sided error component, which allows researchers to recalculate mortality rates while simultaneously deriving a country-specific measure of likely undercount [2]. This statistical approach helps correct for systematic reporting deficiencies, providing a more accurate global picture of infant survival.

Methodological Challenges and Data Limitations

Accurate assessment of infant mortality trends is frequently hampered by reliance on incomplete or non-representative data sources. As noted earlier, a significant portion of child deaths occurs in the neonatal period. Research indicates that available evidence is often based on clinic and hospital administrative records, which are typically confined to specific facilities or geographic areas, thereby limiting the generalizability of findings [4]. This is especially problematic in low-resource settings where many births and deaths occur outside of formal health institutions and go unrecorded in vital registration systems. Historical analyses also face distinct challenges; estimates of past mortality rates are often considered conservative because many are derived from archaeological records of child and infant burials, which are less commonly performed and whose remains are more susceptible to decay over time [17]. These data gaps necessitate sophisticated statistical corrections and modeling to produce reliable estimates for public health planning and monitoring global goals.

Geographic and Social Disparities in Risk

Children continue to face vastly different probabilities of survival based solely on their place of birth [2]. As previously mentioned, sub-Saharan Africa and Southern Asia bear the heaviest burden. Within countries, significant disparities persist along socioeconomic, racial, and ethnic lines. Analytical frameworks for understanding these disparities often evaluate two primary conceptual approaches to race: one treating it as a proxy for geographic ancestry and genetics, and the other understanding it as a social construct with profound impacts on health through pathways like structural racism, differential access to care, and socioeconomic inequality [6]. The social determinants of health, including parental education, household income, and environmental conditions, are powerful drivers of differential infant mortality rates. For example, a multilevel analysis of the 2016 Ethiopian Demographic and Health Survey (EDHS) identified key determinants of infant mortality in the general population, highlighting the complex interplay of individual, household, and community-level factors [5].

Global Frameworks and Measurement

The global awareness of infant mortality as a bellwether for development has been institutionalized through international frameworks. This awareness helped give rise to the United Nations' eight Millennium Development Goals (MDGs), which aimed to capture the multidimensional nature of economic and social progress. Infant and child mortality indicators were central targets within these goals, reflecting their status as composite measures of health system performance, nutritional status, maternal health, and environmental safety. Contemporary monitoring relies on data compiled by global health agencies, with standardized metadata registries defining the indicator for consistent tracking across nations [14]. The persistent inequities in infant survival rates between and within countries underscore that despite overall global progress, the benefits of medical advances and economic growth have not been equitably distributed.

Analytical Approaches to Determinants and Interventions

Identifying the factors that contribute to infant mortality requires research designs capable of disentangling complex causal pathways. The multilevel analysis of EDHS data is one such approach, assessing determinants across different tiers of influence, from individual attributes to broader community characteristics [5]. Furthermore, understanding the impact of large-scale disruptions, such as the COVID-19 pandemic, on infant mortality requires specific analytical methods. Studies have employed interrupted time series analysis to evaluate changes in mortality trends in low- and middle-income countries during the pandemic, though such analyses are often constrained by the same limitations of facility-based administrative data that hamper generalizability [4]. Building on the continuum of care strategy now central to global health frameworks, effective interventions must be informed by robust, context-specific evidence that accounts for the major causes of mortality and the social architecture of risk.

Significance

Infant mortality rate (IMR) is widely regarded as one of the most sensitive and telling indicators of a population's overall health and socioeconomic well-being. Its significance extends far beyond a simple demographic statistic, functioning as a composite measure that reflects the complex interplay of healthcare system quality, economic development, environmental conditions, and social equity [14]. As noted earlier, infant mortality is a fundamental indicator, and its trends provide critical insights into the effectiveness of public health policies and the distribution of societal resources.

A Benchmark for Global Health and Development

The trajectory of global infant and under-5 mortality is a central metric for assessing progress in international development. Between 1990 and 2019, the global under-5 mortality rate (U5MR) decreased by 59%, from 93.0 to 37.7 deaths per 1000 live births, while the annual number of deaths in this age group fell from 12.5 million to 5.2 million [3]. This decline has continued, with the U5MR dropping to an estimated 37 deaths per 1000 live births by 2023 [19]. These reductions are not merely statistical achievements but represent profound improvements in human welfare, driven by concerted global efforts. The awareness generated by such data has been instrumental in shaping international policy agendas, most notably giving rise to the United Nations' Millennium Development Goals (MDGs) and their successor, the Sustainable Development Goals (SDGs), which explicitly target the reduction of preventable child deaths as a multi-dimensional development objective. The measure's utility as a benchmark is enhanced by its stratification, which allows for nuanced analysis of disparities. Data is routinely disaggregated by factors such as:

• Geographic region (e.g., country, sub-national district)
• Socioeconomic status (e.g., household wealth quintile)
• Maternal education level
• Urban versus rural residence [18]

This stratification reveals that national averages often mask severe inequalities. For instance, the under-5 mortality rate in high-income countries can be over ten times lower than the global average [17]. Such disparities make IMR a powerful tool for identifying vulnerable populations and targeting interventions.

An Indicator of Health System Performance and Quality of Care

Perinatal and infant mortality rates are particularly revealing indicators of the quality of a healthcare system, especially around the time of birth. High rates often signal deficiencies in:

• Antenatal care coverage and quality
• Skilled attendance at birth
• Emergency obstetric and newborn care services
• Postnatal care for mothers and infants

The quality of intrapartum and immediate newborn care is crucial, given that nearly half (47%) of all under-5 deaths occur in the neonatal period. Effective interventions in this phase require a functional and accessible health system. The World Health Organization's guidelines, which recommend a minimum of eight antenatal contacts and specific interventions like early ultrasound for gestational dating, are designed to mitigate risks that lead to infant mortality, such as preterm birth [21]. The presence or absence of these services directly influences mortality outcomes. Furthermore, infant mortality data can reflect difficult clinical and ethical decisions within healthcare. "Redirection of care," defined as decisions to withhold certain medical treatments, not escalate care, or implement do-not-resuscitate (DNR) orders, is a documented factor in a subset of infant deaths, particularly among those with severe congenital or genetic disorders [20]. This highlights how mortality statistics can also encompass complex bioethical dimensions of medical practice.

A Proxy for Socioeconomic Conditions and Inequality

Infant mortality is strongly correlated with macroeconomic indicators and is frequently used in comparative studies of national development. Research consistently employs internationally comparable measures of income, such as Gross Domestic Product (GDP) or Gross National Income (GNI) per capita adjusted for purchasing power parity (PPP), to analyze the relationship between economic resources and child survival [18]. The correlation is robust: wealthier nations, on average, exhibit significantly lower IMRs. This relationship is mediated through multiple pathways:

• Greater household resources for nutrition, sanitation, and safe housing
• Higher government capacity to finance and maintain public health infrastructure
• Increased educational attainment, particularly among women
• Lower rates of poverty and material deprivation

Consequently, trends in IMR can serve as a bellwether for broader socioeconomic progress or regression. Stagnant or rising infant mortality may signal economic distress, failing public services, or growing inequality long before other economic indicators reflect the crisis.

A Measure of Resilience and Demographic Impact

The behavior of infant mortality during crises offers insights into societal and health system resilience. The COVID-19 pandemic provided a recent test case. Research evaluating demographic trends during the pandemic's first two years found that while COVID-19 significantly impacted overall life expectancy, global child mortality rates continued their historical decline [22]. This suggests that the mechanisms and programs driving reductions in infant mortality—such as vaccination campaigns, nutritional supplementation, and maternal care—possessed a degree of resilience against the pandemic's disruptions, though sub-national disparities likely widened. Tracking IMR through such shocks is vital for understanding which protective policies are most robust. Demographically, infant mortality is a key component of life expectancy calculations and population projections. High IMRs depress a population's average life expectancy at birth substantially, as the death of an infant represents the loss of many potential years of life. Improvements in infant survival, therefore, are a major driver of increases in life expectancy, contributing to changes in population age structure and growth rates.

A Catalyst for Public Health Action and Accountability

Finally, the widespread adoption of infant mortality as a core indicator has made it a potent catalyst for public health action and political accountability. Its simplicity and emotional resonance make it an effective advocacy tool. Regular reporting by entities like the UN Inter-agency Group for Child Mortality Estimation (UN IGME) creates a system of global monitoring that holds governments and international organizations accountable for progress [3][18]. The publication of estimates with uncertainty intervals (e.g., 90% UI) allows for a more sophisticated interpretation of trends and the confidence with which changes can be assessed [3]. In summary, the significance of infant mortality lies in its multifaceted role as a diagnostic tool for health systems, a barometer of socioeconomic conditions, a benchmark for global equity, and a rallying point for humanitarian investment. Its continued measurement and analysis are indispensable for guiding efforts to improve survival and health for the world's youngest and most vulnerable population.

Applications and Uses

Infant mortality rate (IMR) serves as a foundational metric with wide-ranging applications in public health, economics, and social policy. Its primary utility stems from its sensitivity to a broad spectrum of societal conditions, making it a powerful proxy indicator for overall system performance. The rate is typically expressed as the number of deaths of infants under one year of age per 1,000 live births in a given year, allowing for standardized international comparison [23][14]. Beyond its role as a simple health statistic, the disaggregation and analysis of infant mortality data provide critical insights for targeted intervention and global benchmarking.

A Benchmark for Global Health and Development

The trajectory of global infant and under-5 mortality is a central metric for assessing progress in international development, most notably tracked against targets like the United Nations Sustainable Development Goals (SDGs) [19]. Substantial global progress has been made in reducing childhood mortality since 1990, a trend that has continued even during global disruptions such as the COVID-19 pandemic [19][22]. This decline is a key measure of the effectiveness of transnational health initiatives and resource allocation. International comparisons of IMR reveal profound disparities; for instance, in 2023, the estimated rate for the United States was 5.4 deaths per 1,000 live births, while rates in many low-income countries exceeded 40 per 1,000 [23][14]. These comparisons are essential for holding nations accountable and directing development aid to regions with the greatest need.

An Indicator of Health System Quality and Socioeconomic Conditions

Perinatal and infant mortality rates are particularly sensitive indicators of the quality of healthcare before, during, and after delivery, as well as the broader health status of a nation [19][20]. The causes of death are highly informative: a high proportion of deaths due to preterm birth complications (babies born alive before 37 weeks of pregnancy are completed) often points to deficiencies in prenatal care and maternal health services [21]. Conversely, a high proportion of post-neonatal deaths (occurring between 28 days and one year) may indicate challenges related to nutrition, sanitation, and access to primary care for infectious diseases. Furthermore, research quantifying the contribution of genetic disorders to infant mortality helps assess the capacity of a health system to provide advanced diagnostic and management services [20]. Disaggregating IMR by socioeconomic, racial, and ethnic subgroups within a country—such as the differences reported among race and Hispanic-origin groups following OMB standards—exposes inequities in healthcare access and social determinants of health [8].

A Tool for Economic and Epidemiological Analysis

Infant mortality data are extensively used in economic and demographic research to model the relationship between national wealth and population health outcomes. Systematic reviews and meta-analyses have specifically aimed to quantify the relationship between national income (using internationally comparable measures like GDP per capita purchasing power parity) and infant or under-five mortality in developing countries [9]. This relationship is not linear; gains in survival are typically steepest at lower income levels, demonstrating the high impact of basic interventions. IMR is also a critical variable in calculating key demographic indices, such as life expectancy at birth. Epidemiologists use IMR trends to monitor the impact of specific interventions, disease outbreaks, or policy changes over time, providing a clear, outcome-based measure of success or failure.

Informing Public Health Policy and Intervention

The applications of infant mortality statistics are ultimately operational, directly guiding the creation and evaluation of public health programs. Data on leading causes of infant death inform priority-setting for medical research, clinical guideline development, and public health funding. For example, a high burden of mortality from congenital anomalies may lead to policies promoting folic acid fortification and expanded prenatal screening [20]. The persistent decline in global child mortality, even during the pandemic, suggests the resilience of certain maternal and child health programs, while also highlighting areas requiring reinforced effort [22]. At a programmatic level, IMR is used to:

• Identify high-risk geographic areas or populations for targeted outreach [8]
• Evaluate the effectiveness of specific interventions, such as vaccination campaigns or safe sleep initiatives
• Advocate for legislative changes and resource allocation by demonstrating need and potential impact
• Set national and local health improvement targets and track progress toward them [23][14]

In summary, the measurement and analysis of infant mortality extend far beyond demographic accounting. It functions as a multifaceted tool for global comparison, a diagnostic for health system performance, a correlate for economic development, and a foundational guide for life-saving public health action. Its continued decline globally signifies progress, while persistent disparities underscore the unfinished work of achieving equitable health for all infants [19][22][14].