A methodological note on the relationship between infant mortality and socioeconomic status with evidence from San Antonio, Texas.

A number of previous studies have concluded from social area analyses of medium-size cities that there is no longer a significant correlation between socioeconomic status (SES) and infant mortality in the U.S. To determine if these findings were an artifact of too small samples, the total, neonatal, and postneonatal infant mortality rates were analyzed for 115 census tracts of San Antonio, Texas. The SES of each tract was measured by a score reflecting equally the variables of income, education, and occupation, and allowed assignment of the tracts to 1 of 4 socioeconomic rankings. All 3 infant mortality rates rose as SES decreased, with the most marked relationship being between SES and postneonatal rates. It was also found that of the 3 variables used to measure SES, income bore the strongest relationship to infant mortality. In general it should be noted that social area analysis of infant mortality is limited by the extreme reductions of sample size when additional variables are induced.     

Sudden infant death syndrome and the age‐cause proxy relationship in infancy

Abstract

Evidence from a longitudinal study of the relationship between socioeconomic status and infant mortality in metropolitan Ohio is presented in an effort to throw additional light on the continuing debate over the validity of the age‐cause proxy relationship in infancy. The results indicate that while there is a fairly strong and consistent association between neonatal mortality and endogenous causes of death that is little affected by the classification of Sudden Infant Death Syndrome, the nature of the association between postneonatal mortality and exogenous causes of death varies from weak to moderate depending upon where this cause is included. Additional evidence pertaining to the role of SIDS in contributing to the long‐standing inverse association between infant mortality and socioeconomic status is presented, thus further emphasizing the need for continued research to clarify the etiologic mechanisms of this poorly understood condition.     

Relationships between pregnancy spacing,sex of infants,maternal age,and birth order,and neonatal and post‐neonatal mortality in Bangladesh

Abstract

The relationships between length of the interpregnancy interval, outcome of the pregnancy preceding the interval, sex of the infants, pregnancy order, maternal age, and maternal history of previous child deaths and neonatal and postneonatal mortality were explored in a rural Bangladeshi population using a multiple regression analysis. Specific interactions between the interpregnancy interval, outcome of the pregnancy preceding the interval, sex of the infants, and history of previous child deaths were examined. An inverse relationship was observed between postneonatal mortality and the length of the interpregnancy interval when the pregnancy preceding the interval was a surviving infant. No such trend was observed for neonatal mortality. Post‐neonatal mortality rates among children whose mothers had experienced two or more previous child deaths were essentially the same as that for infants whose mothers had experienced 0–1 child deaths when the interpregnancy intervals were more than 24 months. Although female infants have a lower neonatal mortality than male infants, the neonatal mortality rate for female infants conceived less than twelve months following a male infant birth was higher than for a male infant conceived less than twelve months following another male infant birth. Post‐neonatal mortality is consistently higher for female compared to male infants in all interval categories.     

The relationship between socioeconomic status and infant mortality in metropolitan Ohio, 1999-2001

Empirical evidence has consistently documented the direct relationship between infant mortality and socioeconomic inequality in the United States and numerous other countries. While the majority of these studies reveal an inverse relationship between socioeconomic level and infant mortality, not even this finding is free from disagreement. Furthermore, the specific nature and magnitude of this relationship has varied over time. This study will examine the relationship between socioeconomic status and infant mortality in metropolitan Ohio by using birth and infant death data centered on the 2000 Census. The analyses presented herein will describe and analyze the relationship between infant mortality and socioeconomic status in metropolitan Ohio in the year 2000. The key finding is that in spite of remarkable declines in infant mortality during the past several decades, most notably in neonatal mortality, there continues to be a pronounced inverse association between the infant death rate and the economic status of a population.     

The relationship between socioeconomic status and infant mortality in metropolitan Ohio, 1999–2001

Abstract

Empirical evidence has consistently documented the direct relationship between infant mortality and socioeconomic inequality in the United States and numerous other countries. While the majority of these studies reveal an inverse relationship between socioeconomic level and infant mortality, not even this finding is free from disagreement. Furthermore, the specific nature and magnitude of this relationship has varied over time.

This study will examine the relationship between socioeconomic status and infant mortality in metropolitan Ohio by using birth and infant death data centered on the 2000 Census. The analyses presented herein will describe and analyze the relationship between infant mortality and socioeconomic status in metropolitan Ohio in the year 2000. The key finding is that in spite of remarkable declines in infant mortality during the past several decades, most notably in neonatal mortality, there continues to be a pronounced inverse association between the infant death rate and the economic status of a population.     

Teenage motherhood and infant mortality in Bangladesh: maternal age-dependent effect of parity one

Nuptiality norms in rural Bangladesh favour birth during the teenage years. An appreciable proportion of teenage births are, in fact, second births. This study examines the relationship between teenage fertility and high infant mortality. It is hypothesized that if physiological immaturity is responsible, then the younger the mother, the higher would be the mortality risk, and the effect of mother's 'teenage' on mortality in infancy, particularly in the neonatal period, would be higher for the second than the first births. Vital events recorded by the longitudinal demographic surveillance system in Matlab, Bangladesh, in 1990-92 were used. Logistic regression was used to estimate the effects on early and late neonatal (0-3 days and 4-28 days respectively) and post-neonatal mortality of the following variables: mother's age at birth, parity, education and religion, sex of the child, household economic status and exposure to a health intervention programme. The younger the mother, the higher were the odds of her child dying as a neonate, and the odds were higher for second children than first children of teenage mothers. First-born children were at higher odds of dying in infancy than second births if mothers were in their twenties. Unfavourable mother's socioeconomic conditions were weakly, but significantly, associated with higher odds of dying during late neonatal and post-neonatal periods. The results suggest that physical immaturity may be of major importance in determining the relationship between teenage fertility and high neonatal mortality.     

The age-cause proxy relationship in infant mortality

Data presented in this brief note show that one of the consequences of recent gains in the control of neonatal mortality has been an increase in the frequency of endogenous causes of death in the postneonatal period. Several conclusions are readily apparent from the data presented here. 1st, with respect to total infant mortality, the vast majority of the deaths under 1 year of age today are caused by the endogenous conditions that are most closely associated with the physiological processes of gestation and births. 2nd, both the exogenous and endogenous cause-specific death rates are inversely associated with family income status. The strength of the relationship, as measured by the difference between the death rates of the highest and lowest income areas, is much greater for the environmentally related exogenous causes. Further, there is an obvious tendency for the exogenous causes to account for an increasing proportion of total deaths as income status decreases. While these data support research findings that challenge the validity of the traditional age/cause of death proxy relationship in infancy, they suggest that recommendations for enhancing the neonatal/endogenous relationship by shortening the neonatal period may be premature.     

Influence of birth weight on differences in infant mortality by social class and legitimacy.

OBJECTIVE--To investigate the influence of birth weight on the pronounced social class differences in infant mortality in Britain. DESIGN--Analysis of routine data on births and infant deaths. SETTING--England and Wales. SUBJECTS--All live births and infant deaths, 1983-5. MAIN OUTCOME MEASURE--Mortality in infants by social class, birth weight, and legitimacy according to birth and death certificates. RESULTS--Neonatal and postneonatal mortality (deaths/1000 births) increased with social class. Neonatal and postneonatal mortality was 4.2/1000 and 2.3/1000 respectively for social class I and 6.8/1000 and 5.6/1000 respectively for social class V. Mortality was lower among births registered within marriage (postneonatal 3.5/1000; neonatal 5.2/1000) than among those jointly registered outside marriage (5.1/1000; 6.4/1000); mortality was highest in those solely registered outside marriage (7.2/1000; 7.0/1000). For neonatal mortality the effect of social class varied with birth weight. Social class had little effect on neonatal mortality in low birthweight babies and increasing effect in heavier babies. For postneonatal mortality the effect of social class was similar for all birth weights and was almost as steep as for all birth weights combined. CONCLUSION--Birth weight mediates little of the effect of social class on postneonatal mortality.     

Socioeconomic status and infant mortality among Hispanics in a southwestern city

Recent investigations of infant mortality in the Southwest part of the US have shown that Spanish surname infant death rates are lower than might be expected from the relatively low socioeconomic standing of the Spanish surname population, a phenomenon that appears to be confined to the neonatal componont of the infant mortality rate. The relationship between socioeconomic status (ses) and infant mortality is examined overall and separately within the Anglo and Spanish surname populations of Corpus Christ, Texas. The investigation utilizes data from the 36 Nueces County census tracts. Most recent data on infant, neonatal, and postneonatal mortality was provided by the local health department. Subjects were limited to Anglos and those whites with at least 1 Spanish surname parent. The 1979-1983 cohort is analyzed. Information from the 1980 US census was utilized to divide the 36 census tracts into 3 SES groups: high, medium and low. The most immediately striking aspect of the findings is the significant inverse gradient in Anglos between SES and both the total infant mortality rate (IMR) and the neonatal mortality (NMR), a gradient which is nonexistent in the Spanish surname population as well as overall. In addition, Anglos and Spanish persons differ significantly with respect to all IMRs and NMRs. In the high and medium SES groups and overall, all Anglo rates are lower, while in the low SES group, Spanish surname rates are lower. These findings suggest that, among Anglos, SES is a crucial factor in infant deaths, whereas, among the Spanish surname population, having a medium or high SES does not offer any additional protection against mortality. Alternatively, lower SES does not translate into significantly lower infant mortality among Spanish persons. These findings provide support for the study's hypotheses that the SES-infant mortality association is weaker among Spanish persons than among Anglos. The analysis also shows the importance of analyzing the SES-infant mortality association separately by ethnicity. Studies in larger cities and also studies utilizing matched birth and death records are needed to further elaborate these findings.     

Racial differences in the relationship between infant mortality and socioeconomic status

This study presents an ecological analysis of the relationship between infant mortality and economic status by race in metropolitan Ohio, using census data on mother's residence and economic status determined by the percentage of low-income families living in each area. The analysis updates previous studies as white-non-white comparisons for total infant mortality are examined for the US censuses of 1960, 1970, 1980, 1990 and 2000; and more detailed period- and broad cause-specific rates are presented for 2000. A pronounced inverse association is consistently found between income status and infant mortality for whites, while for non-whites this pattern first emerges in 1979-81, disappears during the 1980s and then returns more strongly during the 1990s. Similarly, the 2000 data reveal a consistent inverse pattern between income status and infant mortality for white and non-white neonatal and postneonatal death rates, as well as exogenous cause-specific death rates. It is concluded that low-income whites and non-whites have infant mortality rates substantially higher than the overall rate for the population. Policy implications are discussed.     

The effect of divorce on infant mortality in a remote area of Bangladesh

The process of divorce is usually lengthy and hazardous, and can start quarrels that can lead to the abuse of women and their children. This study examines the effects of divorce on neonatal and postneonatal mortality of babies born before and after divorce in Teknaf, a remote area of Bangladesh. The longitudinal demographic surveillance system (DSS) followed 1,762 Muslim marriages in 1982-83 for 5 years to record divorce, deaths of spouse, emigration and births. It recorded 2,696 live births during the follow-up period, and their survival status during infancy. Logistic regression models were used to estimate the effect of divorce on neonatal and postneonatal mortality, controlling for maternal age at birth, parity, sex of the child and household economic status. The odds of neonatal and postneonatal deaths among babies born after divorce or less than 12 months before mothers were divorced were more than double the odds of those born to mothers of intact marriages. The odds of postneonatal deaths were two times higher among babies born more than 12 months before divorce happens than their peers. The high mortality of infants born before and after mothers were divorced may reflect how abusive marriage and divorce increase the vulnerability of women and children in rural Bangladesh. Divorce and abuse of women are difficult and intractable social and health problems that must be addressed.     

Infant and child mortality in Pakistan--some trends and differentials

Data from reproductive histories collected in the Population, Labor Force and Migration Survey (PLM) of 1979 are used to analyze trends and differentials in infant and child mortality in Pakistan. Comparisons with the Pakistan Fertility Survey (PFS) findings are also presented. The main concern is to provide from the latest national data, the PLM, direct measures of infant and child mortality and to demonstrate the relatively static and low chances of survival for children in Pakistan. The apparent trends from the PLM and the PFS are similar and seem to confirm that infant and childhood mortality has ceased to decline, at least rapidly, since 1965-69. Neonatal mortality is higher at levels of 70-85 deaths/1000 compared to postneonatal mortality of 40-60 deaths/1000. Improvements in neonatal rates from 1950 until 1975 are only approximately 1/2 of those for postneonatal rates for that period. The relationship between maternal age and mortality in the PLM data confirms that children of youngest mothers experienced the highest rates of infant mortality; mortality is again higher for children of oldest mothers aged 35 and above. The pattern of mortality in the 2 surveys is similar except that in the PFS there was little variation among births higher than 5th order. Sex differentials in mortality are very clear in both surveys. Boys have higher chances of dying in the 1st month of life but then the probability of their surviving from age 1 to 5 years is higher, reflecting the behavioral preference for the male sex in this society. The data also demonstrate an almost monotonic decline in infant and child mortality associated with longer birth intervals. Childhood mortality shows a less clear association with preceding birth interval than does infant mortality. While neonatal mortality is much higher in rural than in urban areas, there are negligible differences in the postneonatal rate. The urban-rural differential continues into childhood, reflecting lower health care and nutrition of children in rural areas. The data confirm the importance of parental education, particularly that of mothers, as a contributor to the health and mortality of infants. Mortality between age 1 and 5 years for children of the rural educated group is lower than that for the urban uneducated indicating the strong influence that education of mothers can have in preventing child loss. The combined evidence from the PFS and PLM data stresses the importance of improving health facilities in the rural areas, in aneffort to reduce the differences in mortality by area of residence. The data from both surveys also suggest the need to restrict motherhood to between the ages of 20 and 34, when obstetrical and health risks are minimal, and indicate the definite advantages of increasing the spacing between children.     

Social class differences in infant mortality in Sweden: comparison with England and Wales.

OBJECTIVES--To investigate social class differences in infant mortality in Sweden in the mid-1980s and to compare their magnitude with that of those found in England and Wales. DESIGN--Analysis of risk of infant death by social class in aggregated routine data for the mid-1980s, which included the linkage of Swedish births to the 1985 census. SETTING--Sweden and England and Wales. SUBJECTS--All live births in Sweden (1985-6) and England and Wales (1983-5) and corresponding infant deaths were analysed. The Swedish data were coded to the British registrar general''s social class schema. MAIN OUTCOME MEASURES--Risk of death in the neonatal and postneonatal period. RESULTS--Taking the non-manual classes as the reference group, in the neonatal period in Sweden the manual social classes had a relative risk for mortality of 1.20 (95% confidence interval 1.02 to 1.43) and those not classified into a social class a relative risk of 1.08 (0.88 to 1.33). In the postneonatal period the equivalent relative risks were 1.38 (1.08 to 1.77) for manual classes and 2.14 (1.65 to 2.79) for the residual; these are similar to those for England and Wales (1.43 (1.36 to 1.51) for manual classes, 2.62 (2.45 to 2.81) for the residual). CONCLUSIONS--The existence of an equitable health care system and a strong social welfare policy in Sweden has not eliminated inequalities in post-neonatal mortality. Furthermore, the very low risk of infant death in the Swedish non-manual group (4.8/1000 live births) represents a target towards which public health interventions should aim. If this rate prevailed in England and Wales, 63% of postneonatal deaths would be avoided.     

The influence of antenatal and maternal factors on stillbirths and neonatal deaths in New South Wales, Australia

This study identified the influences of maternal socio-demographic and antenatal factors on stillbirths and neonatal deaths in New South Wales, Australia. Bivariate and multivariate analyses were used to explore the association of selected antenatal and maternal characteristics with stillbirths and neonatal deaths. The findings of this study showed that stillbirths and neonatal deaths significantly varied by infant sex, maternal age, Aboriginality, maternal country of birth, socioeconomic status, parity, maternal smoking behaviour during pregnancy, maternal diabetes mellitus, maternal hypertension, antenatal care, plurality of birth, low birth weight, place of birth, delivery type, maternal deaths and small gestational age. First-born infants, twins and infants born to teenage mothers, Aboriginal mothers, those who smoked during the pregnancy and those of lower socioeconomic status were at increased risk of stillbirths and neonatal deaths. The most common causes of stillbirths were conditions originating in the perinatal period: intrauterine hypoxia and asphyxia. Congenital malformations, including deformities and chromosomal abnormalities, and disorders related to slow fetal growth, short gestation and low birth weight were the most common causes of neonatal deaths. The findings indicate that very low birth weight (less than 2,000 g) contributed 75.6% of the population-attributable risks to stillbirths and 59.4% to neonatal deaths. Low gestational age (less than 32 weeks) accounted for 77.7% of stillbirths and 87.9% of neonatal deaths. The findings of this study suggest that in order to reduce stillbirths and neonatal deaths, it is essential to include strategies to predict and prevent prematurity and low birth weight, and that there is a need to focus on anti-smoking campaigns during pregnancy, optimizing antenatal care and other healthcare programmes targeted at the socially disadvantaged populations identified in this study.     

Racial/ethnic disparities in infant mortality: the role of behavioral factors

Using the National Maternal and Infant Health Survey 1988 (NMIHS), a nationally representative sample of mothers, we investigate the role of behavioral factors in explaining racial/ethnic disparities in infant mortality. In particular, we focus on the following variables: weight gain during pregnancy, prenatal care utilization, exercise, vitamin use, and substance use during pregnancy. These analyses are conducted by modeling both time of death (neonatal vs. postneonatal) and cause of death (infections, perinatal complications, delivery complications, congenital malformations, SIDS, other causes) outcomes. Our results suggest that behavioral factors are partially responsible for observed race/ethnic differentials in infant mortality, but are not as important as sociostructural determinants such as SES.     

Heredity of joint diseases

Abstract

This research examines the infant mortality/socioeconomic status relationship in Toledo, Ohio, for the years centering around 19S0, 1960, and 1970 in order to depict variables that contributed most to infant mortality for each time period. Zero‐order correlation coefficients demonstrated that the relationship has widened mainly as a result of an increasing inverse neonatal/socioeconomic pattern which was due in part to a “cause‐period cross‐over effect” (exogenous causes of death were contributing to deaths in the neonatal period in 1970). Further examination suggested that the status variables through which the differentials were operating have shifted from one time period to another. In 1950, crowded housing conditions and unemployment were primarily responsible; in 1960, it was housing and income; and in 1970, marital instability and income predominated. This paper suggests that as new social phenomena emerge they quickly affect sensitive indicators of well‐being such as the infant mortality rate.     

Factors influencing prereproductive mortality in the isolated and preindustrial western Mediterranean population of La Alpujarra, 1900-1950

We study the effects of several variables on the prereproductive mortality pattern in the isolated and rural population of La Alpujarra, located on the western Mediterranean coast (southeast Spain), in the first half of the 20th century. The study is a retrospective analysis from a total sample of 2,200 deliveries, 2,085 of which were born alive and 171 of which did not survive to the 20th birthday. The potential influences of birthdate of children, twinning, firstborn, parental inbreeding, and sex on Alpujarran mortality were analyzed through logistic regression. Parity, family size, and birth interval effects were estimated through the difference between observed and expected mortality rates. In every case four age groups of mortality were considered because of the large influence of child growth: neonatal (less than 1 month of life), postneonatal infant (between 1 month and 1 year old), childhood (1-5 years old), and youth (5-20 years old). The Alpujarran prereproductive mortality pattern can be summarized as the result of three main risk factors: biodemographic, biomechanical, and social and health determinants. In general, every factor showed a decreased effect as children grew. The most significant determinants were birthdate of children, which is more related to increased mother's awareness of child care than to health improvement, and family size associated with decreasing alimentary resources as the sibling number increased. Male mortality was higher than female mortality in children older than 1 year but not for infant mortality, possibly as a result of a reproductive behavior favorable to males. Although firstborn status and twinning appeared associated with high mortality, maternal age and birth interval were related to low risk, but these influences always ceased after the first month of life. Parental inbreeding did not show any effect on infant, childhood, or youth mortality.     

Racial differences in infant mortality attributable to birth defects in the United States, 1989-2002

BACKGROUND: The objective is to study racial differences in infant mortality attributable to birth defects (IMBD) in the United States. METHODS: We analyzed 1989-1991 and 1995-2002 linked birth/death files for trends and racial differences in IMBD by selected categories of birth defects for infants of non-Hispanic white, non-Hispanic black, and Hispanic mothers. RESULTS: In 1989-2002, the IMBD rates declined. However, the decline in postneonatal mortality attributable to birth defects (PMBD) rate was significantly slower than that of overall postneonatal mortality. The adjusted rate ratio for non-Hispanic black and Hispanic versus non-Hispanic white for neonatal mortality attributable to birth defects (NMBD) remained unchanged from 1989-1991 through 2000-2002. For PMBD, it increased from 0.97 (95% confidence interval [CI], 0.90-1.13) in 1989-1991 to 1.12 (95% CI, 1.04-1.21) in 2001-2002 and from 1.08 (95% CI, 1.00-1.16) to 1.18 (95% CI, 1.10-1.27) for non-Hispanic black and Hispanic, respectively. Infant mortality due to cardiovascular and central nervous system defects were the main contributors to the increased racial disparities in PMBD rates. CONCLUSIONS: The disparity in PMBD between infants of non-Hispanic black and Hispanic mothers and infants of non-Hispanic white mothers increased significantly from 1989-1991 to 2000-2002. Further studies are needed to assess the extent to which delays in care or lack of access to care for infants with birth defects might be contributing to the disparity in IMBD.     

Perinatal mortality and adverse pregnancy outcomes in a low-income rural population of women who smoke

We describe adverse pregnancy outcomes, including congenital anomalies, fetal, neonatal, and infant mortality among a Missouri population of low-income, rural mothers who participated in two randomized smoking cessation trials. In the Baby BEEP (BB) trial, 695 rural women were recruited from 21 WIC clinics with 650 women's pregnancy outcomes known (93.5% retention rate). Following the BB trial, 298 women who had a live infant after November 2004 were recruited again into and completed the Baby Beep for Kids (BBK) trial. Simple statistics describing the population and perinatal and postneonatal mortality rates were calculated. Of the adverse pregnancy outcomes (n = 79), 29% were spontaneous abortions of less than 20 weeks' gestation, 23% were premature births, and 49% were identified birth defects. The perinatal mortality rate was 15.9 per 1000 births (BB study) compared with 8.6 per 1000 births (state of Missouri) and 8.5 per 1000 births (United States). The postneonatal infant mortality rate was 13.4 per 1000 live births (BBK) compared with 2.1 per 1000 live births (United States). The health disparity in this population of impoverished, rural, pregnant women who smoke, particularly in regard to perinatal and infant deaths, warrants attention.     

Underlying and proximate determinants of diarrhoea-specific infant mortality rates among municipalities in the state of Céara, north-east Brazil: an ecological study

This ecological study examines the variations in diarrhoea-specific infant mortality rates among municipalities in the State of Ceará, north-east Brazil, using data from a community health workers' programme. Diarrhoea is the main cause of postneonatal deaths in Ceará, and diarrhoea mortality rates vary substantially among municipalities, from 7 to 50 per thousand live births. To determine the inter-relationships between potential predictors of diarrhoea-specific infant mortality, eleven variables were classified into proximate determinants (i.e. adequate weight gain and exclusive breast-feeding in first 4 months) and underlying determinants (i.e. health services and socioeconomic variables). The health services variables included percentage with prenatal care up-to-date, participation in growth monitoring and immunization up-to-date, while the socioeconomic factors included female illiteracy rate, per capita gross municipality product and percentage of households with low income, percentage of households with inadequate water supply and inadequate sanitation, and urbanization. Using linear regression analysis variables were included from each group to build regression models. The significant determinants of variability in diarrhoea-specific infant mortality between municipalities were prevalence of infants exclusively breast-feeding, percentage of infants with adequate weight gain, percentage of pregnant women with prenatal care up-to-date, female illiteracy rate and inadequate water supply. These findings suggest that community-based promotion of exclusive breast-feeding in the first 4 months and care-giving behaviours that prevent weight faltering, including weaning practices and feeding during and following diarrhoea episodes, may further reduce municipality-level diarrhoea-specific mortality. Primary heath care strategies addressing these two proximate determinants provide only a partial solution to reducing diarrhoeal disease mortality. Improvements in municipal health services (prenatal care) and socioeconomic status variables, including water supply and maternal education, can also contribute to reduction of infant mortality due to diarrhoea. These results may be used by government health officials to set priorities by considering not only the strength of the association between selected risk factors and diarrhoea mortality rates, but also the prevalence of the risk factors being considered at the municipality level. Finally, the methods used are applicable to other settings with community-based primary health care decentralized to the state or municipal level.