Early childhood mortality in a Brazilian cohort: the roles of birthweight and socioeconomic status

Air Pollution and Racial Disparities in Pregnancy Outcomes in the United States: A Systematic Review

BACKGROUND

Exposure to air pollutants and other environmental factors increases the risk of adverse pregnancy outcomes. There is growing evidence that adverse outcomes related to air pollution disproportionately affect racial and ethnic minorities. The objective of this paper is to explore the importance of race as a risk factor for air pollution-related poor pregnancy outcomes.

METHODS

Studies investigating the effects of exposure to air pollution on pregnancy outcomes by race were reviewed. A manual search was conducted to identify missing studies. Studies that did not compare pregnancy outcomes among two or more racial groups were excluded. Pregnancy outcomes included preterm births, small for gestational age, low birth weight, and stillbirths.

RESULTS

A total of 124 articles explored race and air pollution as risk factors for poor pregnancy outcome. Thirteen percent of these (n=16) specifically compared pregnancy outcomes among two or more racial groups. Findings across all reviewed articles showed more adverse pregnancy outcomes (preterm birth, small for gestational age, low birth weight, and stillbirths) related to exposure to air pollution among Blacks and Hispanics than among non-Hispanic Whites.

CONCLUSION

Evidence support our general understanding of the impact of air pollution on birth outcomes and, specifically, of disparities in exposure to air pollution and birth outcomes for infants born to Black and Hispanic mothers. The factors driving these disparities are multifactorial, mostly social, and economic factors. Reducing or eliminating these disparities require interventions at individual, community, state, and national level.

Effects of recruiting midwives into family physician program on the percentage of low birth weight (LBW) infants in rural areas of Kurdistan

Background: LBW is an important factor that can affect infant mortality and represents an index of economic and social development. It is expected that an increase in the density of midwives attending family physician programs will lead to a decrease in LBW in health centers. This study aimed to compare the percentage of LBW infants before and after the implementation of the family physician program in health centers with and without an increase in midwives density.

Methods: This cross-sectional study compared the percentage of LBW infants before and after the implementation of family physician programs in rural health centers with and without changes in midwives density in Kurdistan. In this study, we included 668 mothers of 2-month-old children and administered structured interviews in 2005 and 2013. Data were analyzed using the difference-indifferences and the Matchit statistical models.

Results: The Matchit model showed a significant average percentage increase 0.08 (0.006–0.17) in LBW infants born between 2005 and 2013 in health centers where the density of midwives increased compared with those where it remained unchanged. The difference-in-differences model showed that the odds ratio of LBW infants is increased by more than twice among participants who had a history of caesarean section.

Conclusion: The results of this study showed that an increase in the density of midwives in a family physician program did not have an impact on reducing the percentage of LBW infants born between 2005 and 2013, in health centers where the density of midwives augmented compared to those where it remained unaltered; it indicated that the increase in the density of midwives alone was not efficient. On the other hand, the results of our study show an increase in the risk of infants born at a LBW due to caesarean section. It is recommended that obstetricians and gynecologists must strictly control pregnancies and avoid unnecessary termination of pregnancy

MATERNAL HEALTH-SEEKING BEHAVIOUR AND UNDER-FIVE MORTALITY IN ZIMBABWE

Under-five mortality remains a major public health challenge in sub-Saharan Africa. Zimbabwe is one of the countries in the region that failed to achieve Millennium Developmental Goal 4 in 2015. The objective of this study was to examine the extent to which maternal health-seeking behaviour prior to and during pregnancy and post-delivery influences the likelihood of under-five mortality among Zimbabwean children. The study was cross-sectional and data were extracted from the 2010/11 Zimbabwe Demographic and Health Survey (ZDHS). The study sample comprised 5155 children who were born five years preceding the 2010/11 ZDHS to a sample of 4128 women of reproductive age (15-49 years). Cox Proportional Hazard regression modelling was used to examine the relationship between maternal health-seeking behaviour and under-five mortality. The results showed that maternal health-seeking behaviour factors are associated with the risk of dying during childhood. Children born to mothers who had ever used contraceptives (HR: 0.38, CI 0.28-0.51) had a lower risk of dying during childhood compared with children born to mothers who had never used any contraceptive method. The risk of under-five mortality among children who had a postnatal check-up within two months after birth (HR: 0.36, CI 0.23-0.56) was lower than that of children who did not receive postnatal care. Small birth size (HR: 1.70, CI 1.20-2.41) and higher birth order (2+) increased the risk of under-five mortality. Good maternal health-seeking behaviour practices at the three critical stages around childbirth have the potential to reduce under-five mortality. Therefore, public health programmes should focus on influencing health-seeking behaviour among women and removing obstacles to effective maternal health-seeking behaviour in Zimbabwe.

Universal health care and equity: evidence of maternal health based on an analysis of demographic and household survey data

INTRODUCTION

The drive toward universal health coverage (UHC) is central to the post 2015 agenda, and is incorporated as a target in the new Sustainable Development Goals. However, it is recognised that an equity dimension needs to be included when progress to this goal is monitored. WHO have developed a monitoring framework which proposes a target of 80% coverage for all populations regardless of income and place of residence by 2030, and this paper examines the feasibility of this target in relation to antenatal care and skilled care at delivery.

METHODOLOGY

We analyse the coverage gap between the poorest and richest groups within the population for antenatal care and presence of a skilled attendant at birth for countries grouped by overall coverage of each maternal health service. Average annual rates of improvement needed for each grouping (disaggregated by wealth quintile and urban/rural residence) to reach the goal are also calculated, alongside rates of progress over the past decades for comparative purposes.

FINDINGS

Marked inequities are seen in all groups except in countries where overall coverage is high. As the monitoring framework has an absolute target countries with currently very low coverage are required to make rapid and sustained progress, in particular for the poorest and those living in rural areas. The rate of past progress will need to be accelerated markedly in most countries if the target is to be achieved, although several countries have demonstrated the rate of progress required is feasible both for the population as a whole and for the poorest.

CONCLUSIONS

For countries with currently low coverage the target of 80% essential coverage for all populations will be challenging. Lessons should be drawn from countries who have achieved rapid and equitable progress in the past.

Cohort Profile Update: The 1982 Pelotas (Brazil) Birth Cohort Study

In this manuscript, we update the profile of the 1982 Pelotas Birth Cohort Study.In 1982, 5914 live births whose families lived in the urban are of Pelotas were enrolled in the cohort. In 2012–13, we tried to locate the whole original cohort; 3701 participants were interviewed who, added to the 325 known deaths, represented a follow-up rate of 68.1%. In contrast to the previous home interviews, in this wave all participants were invited to visit the research clinic to be interviewed and examined. The visit was carried out at a mean age of 30.2 years and mainly focused on four categories of outcomes: (i) mental health; (ii) body composition; (iii) precursors of complex chronic diseases; and (iv) human capital. Requests for collaboration by outside researchers are welcome.

Social, economic, political and health system and program determinants of child mortality reduction in China between 1990 and 2006: A systematic analysis

Background

Between 1990 and 2006, China reduced its under-five mortality rate (U5MR) from 64.6 to 20.6 per 1000 live births and achieved the fourth United Nation’s Millennium Development Goal nine years ahead of target. This study explores the contribution of social, economic and political determinants, health system and policy determinants, and health programmes and interventions to this success.

Methods

For each of the years between 1990 and 2006, we obtained an estimate of U5MR for 30 Chinese provinces from the annual China Health Statistics Yearbook. For each year, we also obtained data describing the status of 8 social, 10 economic, 2 political, 9 health system and policy, and six health programmes and intervention indicators for each province. These government data are not of the same quality as some other health information sources in modern China, such as articles with primary research data available in Chinese National Knowledge Infrastructure (CNKI) and Wan Fang databases, or Chinese Maternal and Child Mortality Surveillance system. Still, the comparison of relative changes in underlying indicators with the undisputed strong general trend of childhood mortality reduction over 17 years should still capture the main effects at the macro-level. We used multivariate random effect regression models to determine the effect of 35 indicators individually and 5 constructs defined by factor analysis (reflecting effects of social, economic, political, health systems and policy, and health programmes) on the reduction of U5MR in China.

Results

In the univariate regression applied with a one-year time lag, social determinants of health construct showed the strongest crude association with U5MR reduction (R² = 0.74), followed by the constructs for health programmes and interventions (R² = 0.65), economic (R² = 0.47), political (R² = 0.28) and health system and policy determinants (R² = 0.26), respectively. Similarly, when multivariate regression was applied with a one-year time lag, the social determinants construct showed the strongest effect (beta = 11.79, P < 0.0001), followed by the construct for political factors (beta = 4.24, P < 0.0001) and health programmes and interventions (beta = −3.45, P < 0.0001). The 5 studied constructs accounted for about 80% of variability in U5MR reduction across provinces over the 17-year period.

Conclusion

Vertical intervention programs, health systems strengthening or economic growth alone may all fail to achieve the desired reduction in child mortality when improvement of the key social determinants of health is lagging behind. To accelerate progress toward MDG4, low- and middle-income countries should undertake appropriate efforts to promote maternal education, reduce fertility rates, integrate minority populations and improve access to clean water and safe sanitation. A cross-sectoral approach seems most likely to have the greatest impact on U5MR.

Risk factors and a predictive model for under-five mortality in Nigeria: evidence from Nigeria demographic and health survey

Background

Under-5 mortality is a major public health challenge in developing countries. It is essential to identify determinants of under-five mortality (U5M) childhood mortality because these will assist in formulating appropriate health programmes and policies in order to meet the United Nations MDG goal. The objective of this study was to develop a predictive model and identify maternal, child, family and other risk factors associated U5M in Nigeria.

Methods

Population-based cross-sectional study which explored 2008 demographic and health survey of Nigeria (NDHS) with multivariable logistic regression. Likelihood Ratio Test, Hosmer-Lemeshow Goodness-of-Fit and Variance Inflation Factor were used to check the fit of the model and the predictive power of the model was assessed with Receiver Operating Curve (ROC curve).

Results

This study yielded an excellent predictive model which revealed that the likelihood of U5M among the children of mothers that had their first marriage at age 20-24 years and ≥ 25 years declined by 20% and 30% respectively compared to children of those that married before the age of 15 years. Also, the following factors reduced odds of U5M: health seeking behaviour, breastfeeding children for > 18 months, use of contraception, small family size, having one wife, low birth order, normal birth weight, child spacing, living in urban areas, and good sanitation.

Conclusions

This study has revealed that maternal, child, family and other factors were important risk factors of U5M in Nigeria. This study has identified important risk factors that will assist in formulating policies that will improve child survival.

Reducing childhood mortality from diarrhea and lower respiratory tract infections in Brazil

OBJECTIVE

To evaluate the effects of the Family Health Program (FHP), a strategy for reorganization of primary health care in Brazil, on mortality of children younger than 5 years, particularly from diarrheal diseases and lower respiratory tract infections.

METHODS

Mortality rates and the extent of FHP coverage from 2000 to 2005 was evaluated from the 2601 (of 5507) Brazilian municipalities with an adequate quality of vital information. A multivariable regression analysis for panel data was conducted by using a negative binomial model with fixed effects, adjusted for relevant demographic and socioeconomic covariates.

RESULTS

A statistically significant negative association was observed between FHP coverage levels, classified as none (the reference category), low (<30%), intermediate (>or=30% and <70%), or high (>or=70%), and all analyzed mortality rates, with a reduction of 4% (95% confidence interval [CI]: 2%-6%), 9% (95% CI: 7%-12%), and 13% (95% CI: 10%-15%), respectively, on mortality rates or children younger than 5. The greatest effect was on postneonatal mortality. Reductions of 31% (95% CI: 20%-40%) and 19% (95% CI: 8%-28%) in mortality rates from diarrheal diseases and lower respiratory infections, respectively, were found in the group of municipalities with the highest FHP coverage.

CONCLUSIONS

The FHP, one of the largest comprehensive primary health care programs in the world, was effective in reducing overall mortality of children younger than 5, and particularly deaths related to diarrheal diseases and lower respiratory tract infections.

Socioeconomic disparities in adverse birth outcomes: a systematic review

CONTEXT

Adverse birth outcomes, such as preterm birth and low birth weight, have serious health consequences across the life course. Socioeconomic disparities in birth outcomes have not been the subject of a recent systematic review. The aim of this study was to systematically review the literature on the association of socioeconomic disadvantage with adverse birth outcomes, with specific attention to the strength and consistency of effects across socioeconomic measures, birth outcomes, and populations.

EVIDENCE ACQUISITION

Relevant articles published from 1999 to 2007 were obtained through electronic database searches and manual searches of reference lists. English-language studies from industrialized countries were included if (1) study objectives included examination of a socioeconomic disparity in a birth outcome and (2) results were presented on the association between a socioeconomic predictor and a birth outcome related to birth weight, gestational age, or intrauterine growth. Two reviewers extracted data and independently rated study quality; data were analyzed in 2008-2009.

EVIDENCE SYNTHESIS

Ninety-three of 106 studies reported a significant association, overall or within a population subgroup, between a socioeconomic measure and a birth outcome. Socioeconomic disadvantage was consistently associated with increased risk across socioeconomic measures, birth outcomes, and countries; many studies observed racial/ethnic differences in the effect of socioeconomic measures.

CONCLUSIONS

Socioeconomic differences in birth outcomes remain pervasive, with substantial variation by racial or ethnic subgroup, and are associated with disadvantage measured at multiple levels (individual/family, neighborhood) and time points (childhood, adulthood), and with adverse health behaviors that are themselves socially patterned. Future reviews should focus on identifying interventions to successfully reduce socioeconomic disparities in birth outcomes.

Tackling health inequities in Chile: maternal, newborn, infant, and child mortality between 1990 and 2004

OBJECTIVES

We analyzed trends in maternal, newborn, and child mortality in Chile between 1990 and 2004, after the introduction of national interventions and reforms, and examined associations between trends and interventions.

METHODS

Data were provided by the Chilean Ministry of Health on all pregnancies between 1990 and 2004 (approximately 4,000,000). We calculated yearly maternal mortality ratios, stillbirth rates, and mortality rates for neonates, infants (aged > 28 days and < 1 year), and children aged 1 to 4 years. We also calculated these statistics by 5-year intervals for Chile's poorest to richest district quintiles.

RESULTS

During the study period, the maternal mortality ratio decreased from 42.1 to 18.5 per 100,000 live births. The mortality rate for neonates decreased from 9.0 to 5.7 per 1000 births, for infants from 7.8 to 3.1 per 1000 births, and for young children from 3.1 to 1.7 per 1000 live births. The stillbirth rate declined from 6.0 to 5.0 per 1000 births. Disparities in these mortality statistics between the poorest and richest district quintiles also decreased, with the largest mortality reductions in the poorest quintile.

CONCLUSIONS

During a period of socioeconomic development and health sector reforms, Chile experienced significant mortality and inequity reductions.

Estimating child mortality due to diarrhoea in developing countries

OBJECTIVE

The major objective of this study is to provide estimates of diarrhoea mortality at country, regional and global level by employing the Child Health Epidemiology Reference Group (CHERG) standard.

METHODS

A systematic and comprehensive literature review was undertaken of all studies published since 1980 reporting under-5 diarrhoea mortality. Information was collected on characteristics of each study and its population. A regression model was used to relate these characteristics to proportional mortality from diarrhoea and to predict its distribution in national populations.

FINDINGS

Global deaths from diarrhoea of children aged less than 5 years were estimated at 1.87 million (95% confidence interval, CI: 1.56-2.19), approximately 19% of total child deaths. WHO African and South-East Asia Regions combined contain 78% (1.46 million) of all diarrhoea deaths occurring among children in the developing world; 73% of these deaths are concentrated in just 15 developing countries.

CONCLUSION

Planning and evaluation of interventions to control diarrhoea deaths and to reduce under-5 mortality is obstructed by the lack of a system that regularly generates cause-of-death information. The methods used here provide country-level estimates that constitute alternative information for planning in settings without adequate data.

Similarity between neonatal profile and socioeconomic index: a spatial approach

This study aims to compare neonatal characteristics and socioeconomic conditions in Rio de Janeiro city neighborhoods in order to identify priority areas for intervention. The study design was ecological. Two databases were used: the Brazilian Population Census and the Live Birth Information System, aggregated by neighborhoods. Spatial analysis, multivariate cluster classification, and Moran's I statistics for detection of spatial clustering were used. A similarity index was created to compare socioeconomic clusters with the neonatal profile in each neighborhood. The proportions of Apgar score above 8 and cesarean sections showed positive spatial correlation and high similarity with the socioeconomic index. The proportion of low birth weight infants showed a random spatial distribution, indicating that at this scale of analysis, birth weight is not sufficiently sensitive to discriminate subtler differences among population groups. The observed relationship between the neighborhoods' neonatal profile (particularly Apgar score and mode of delivery) and socioeconomic conditions shows evidence of a change in infant health profile, where the possibility for intervention shifts to medical services and the Apgar score assumes growing significance as a risk indicator.

Predicting the distribution of under-five deaths by cause in countries without adequate vital registration systems

BACKGROUND

The absence of complete vital registration and atypical nature of the locations where epidemiological studies of cause of death in children are conducted make it difficult to know the true distribution of child deaths by cause in developing countries. A credible method is needed for generating valid estimates of this distribution for countries without adequate vital registration systems.

METHODS

A systematic review was undertaken of all studies published since 1980 reporting under-5 mortality by cause. Causes of death were standardized across studies, and information was collected on the characteristics of each study and its population. A meta-regression model was used to relate these characteristics to the various proportional mortality outcomes, and predict the distribution in national populations of known characteristics. In all, 46 studies met the inclusion criteria.

RESULTS

Proportional mortality outcomes were significantly associated with region, mortality level, and exposure to malaria; coverage of measles vaccination, safe delivery care, and safe water; study year, age of children under surveillance, and method used to establish definitive cause of death. In sub-Saharan Africa and in South Asia, the predicted distribution of deaths by cause was: pneumonia (23% and 23%), malaria (24% and <1%), diarrhoea (22% and 23%), 'neonatal and other' (29% and 52%), measles (2% and 1%).

CONCLUSIONS

For countries without adequate vital registration, it is possible to estimate the proportional distribution of child deaths by cause by exploiting systematic associations between this distribution and the characteristics of the populations in which it has been studied, controlling for design features of the studies themselves.

Birthweight and risk of overall and cause-specific childhood mortality

Early life events have important short- and long-term consequences. It is clear from previous studies that birthweight is associated with infant mortality and with childhood and adult morbidities. However, few studies have focused on the relationship between birthweight and childhood mortality. To assess this relationship, we conducted a population-based case-control study of children born during 1968-96 in Washington state. Cases consisted of 6247 children who died at 1-19 years of age. A total of 31 074 controls were matched five to one to cases by birth year. Compared with children with a birthweight of 3000-3499 g, children with lower birthweights had a greater risk of childhood mortality. These lower birthweight children had increased risks of childhood deaths from infectious diseases, congenital anomalies, central nervous system diseases and heart disease, but not of deaths resulting from accidents, cancer, suicide or homicide. The magnitude of these risks differed somewhat by age. Our results suggest that birthweight exerts important influences on children's risk of age-specific and cause-specific mortalities, particularly those with a strong biological component.

Social inequalities in health within countries: not only an issue for affluent nations

While interest in social disparities in health within affluent nations has been growing, discussion of equity in health with regard to low- and middle-income countries has generally focused on north-south and between-country differences, rather than on gaps between social groups within the countries where most of the world's population lives. This paper aims to articulate a rationale for focusing on within- as well as between-country health disparities in nations of all per capita income levels, and to suggest relevant reference material, particularly for developing country researchers. Routine health information can obscure large inter-group disparities within a country. While appropriately disaggregated routine information is lacking, evidence from special studies reveals significant and in many cases widening disparities in health among more and less privileged social groups within low- and middle- as well as high-income countries: avoidable disparities are observed not only across socioeconomic groups but also by gender, ethnicity, and other markers of underlying social disadvantage. Globally, economic inequalities are widening and, where relevant information is available, generally accompanied by widening or stagnant health inequalities. Related global economic trends, including pressures to cut social spending and compete in global markets, are making it especially difficult for lower-income countries to implement and sustain equitable policies. For all of these reasons, explicit concerns about equity in health and its determinants need to be placed higher on the policy and research agendas of both international and national organizations in low-, middle-, and high-income countries. International agencies can strengthen or undermine national efforts to achieve greater equity. The Primary Health Care strategy is at least as relevant today as it was two decades ago: but equity needs to move from being largely implicit to becoming an explicit component of the strategy, and progress toward greater equity must be carefully monitored in countries of all per capita income levels. Particularly in the context of an increasingly globalized world, improvements in health for privileged groups should suggest what could, with political will, be possible for all.

Low birth weight and morbidity from diarrhea and respiratory infection in northeast Brazil

OBJECTIVE

To compare morbidity and mortality rates of low birth weight (LBW) and appropriate birth weight infants born at term, focusing on diarrheal and respiratory infections.

STUDY DESIGN

A cohort of 133 LBW infants (1500 to 2499 gm) and 260 appropriate birth weight infants (3000 to 3499 gm), individually matched by sex and season of birth, were followed for the first 6 months of life. None had congenital anomalies and all were from poor families living in the interior of Pernambuco, northeast Brazil. Data on infant deaths, hospitalizations, and morbidity were collected prospectively through daily home visits (except Sundays) from birth through week 8, then twice weekly for weeks 9 to 26. The effects of birth weight were assessed with a variety of multivariable techniques, controlling for confounders.

RESULTS

Of the LBW infants, 56% were wasted (thin), 23% were stunted, and 17% were both wasted and stunted. The LBW infants (median 2380 gm) experienced a sevenfold higher mortality rate and fourfold higher rate of hospitalization than appropriate birth weight infants. Almost all deaths and hospitalizations were in the postneonatal period. The LBW infants also experienced 33% more days with diarrhea and 32% more days with vomiting (p = 0.003 in each case). The prevalences of cough and fever were not significantly different.

CONCLUSIONS

Infant deaths, hospitalizations, and diarrheal morbidity are increased in term LBW infants who have only a modest weight deficit.

Social causes of low birth weight

The manifest importance of reducing the incidence of low birth weight is most obvious for the first year of life: low birth weight is the single most important factor affecting infant morbidity and mortality. However, there is growing evidence that the adverse consequences of low birth weight continue throughout the life cycle. This review deals primarily with social causes of low birth weight.

Low birthweight as a determinant of infectious disease mortality: a methodological evaluation

Low birthweight (LBW) is cited as an important determinant of infectious disease mortality during infancy, both in developed and developing countries. We applied methodological standards to evaluate the scientific validity and clinical applicability of epidemiological studies of this relationship. Three published studies, all reporting an elevation of the risk of infectious disease mortality in infants born with LBW, were identified. Noteworthy methodological deficiencies found in one or more studies included failure to obtain objective data about birthweight and gestational age for a high proportion of study subjects, lack of explicit criteria for assigning causes of death, failure to safeguard against biases in assessment of cause of death and inadequate control for potential confounding variables. In addition, clinical application of the results of these studies was limited by lack of exploration of the roles of preterm birth vs. small-for-gestational-age (SGA) birth, as well as by inattention to the role of congenital anomalies, in explaining the elevated risk. Although our evaluation does not necessarily negate the results of these studies, the failure of any of the studies to comply with all of the standards highlights the need for further research to provide credible evidence regarding the presence and strength of a relationship between LBW and infectious disease mortality in both developed and developing countries.

Subcutaneous fat changes in low-income lactating mothers and growth of breast-fed infants

OBJECTIVE

We studied changes in body fat of lactating mothers and its relationship to milk fat and growth of exclusively breast-fed infants during the first 3 months of life.

METHOD

Changes in body fat measured by body mass index (BMI) and skinfold thickness (triceps, suprailiac, subscapular, pectoral) of 39 low socioeconomic status women were measured every 15 days during the first 3 months postpartum. Milk fat concentrations and growth of exclusively breast-fed infants were followed at the same intervals. Attained growth (ponderal and linear) of infants was analyzed through multivariate analyses against changes in maternal adiposity (BMI and sum of skinfolds), weight, and milk fat concentrations.

RESULTS

There was a decrease in maternal skinfold thickness from the 15th day postpartum. Milk fat concentrations decreased significantly only at the second month of lactation.

CONCLUSION

Statistical model adjustments for duration of study, milk fat concentration, and birth weight of infants explained 88% of variance in infant growth (r2 = 0.886, p = 0.0001).

Determinants of infant and early childhood mortality in Cameroon: the role of socioeconomic factors, housing characteristics, and immunization status

This study examines factors impinging on the survival of children in Cameroon using longitudinal data collected by the United Nations Demographic Training and Research Institute of Yaoundé, Cameroon. It deals especially with the role of socioeconomic factors (mother's education, employment, marital status, ethnicity, and household income), housing characteristics (construction materials, power source, source of water supply, extent of crowding), and immunization status on infant and child mortality. Two-state parametric and nonparametric hazards models for the risk of death at any time within the course of the study are used, with and without accounting for unmeasured heterogeneity. Overall, overcrowding has robust deleterious effects on infant and child survival. As regards the effects of socioeconomic variables, the robustness of the effects of household income and ethnic differentials are unchanged, even after controlling for unmeasured heterogeneity; the deleterious effects of marital status are also apparent, but these effects are largely explained by unmeasured covariates. The data also suggest that the protective effects of full immunization status are robust and not contaminated by confounding factors, at least in the first 16 months of life. These findings provide solid ground to support immunization programs and efforts as a means to reduce significantly infant and child mortality.