Birth weight-specific causes of infant mortality, United States, 1980

To describe underlying causes of infant death by birth weight, we used data from the 1980 National Infant Mortality Surveillance project and aggregated International Classification of Diseases codes into seven categories: perinatal conditions, infections, congenital anomalies, injuries, sudden infant death syndrome (SIDS), other known causes, and nonspecific or unknown causes. Compared with heavier infants, infants with birth weights of 500-2,499 grams (g) are at increased risk of both neonatal and postneonatal death for virtually all causes. Sixty-two percent of neonatal deaths (under 28 days of life) were attributed to "conditions arising in the perinatal period," as defined using codes from the International Classification of Diseases. Prematurity-low birth weight and respiratory distress syndrome (RDS) were the leading causes of such deaths among infants with birth weights of 500-2,499 g, while birth trauma-hypoxia-asphyxia and other perinatal respiratory conditions were the leading causes among heavier infants. For all birth weight groups, congenital anomalies were the second leading cause, representing 27 percent of neonatal deaths. Although perinatal conditions caused nearly one-third of postneonatal deaths (28 days to under 1 year of life) among infants with birth weights of 500-1,499 g, for the other birth weight groups these conditions were much less important; predominant causes of postneonatal death were sudden infant death syndrome (SIDS), congenital anomalies, infections, and injuries. Black infants had a roughly twofold higher risk of neonatal and postneonatal death than did white infants for all causes except congenital anomalies, which occurred with almost equal frequency in blacks and whites. However, for infants with birth weights of 500-2,499 g, blacks had lower risks of neonatal death from RDS and congenital anomalies. Between 1960 (the latest year for which national birth weight-specific mortality statistics had been available) and 1980, SIDS emerged as a major diagnostic rubric. Otherwise, except for infections and congenital anomalies among infants with birth weights of 500-1,499 g, all causes of death declined in frequency among all birth weight groups.     

Birth weight-specific infant mortality due to congenital anomalies, 1960 and 1980

The impact of mortality due to congenital anomalies in single-delivery births was compared in 1960 and 1980 birth cohorts; data were used from the 1960 National Center for Health Statistics national linkage of birth and death certificates and the 1980 National Infant Mortality Surveillance project. In 1960 there were 14,714 deaths due to congenital anomalies, compared with 8,674 in 1980, a 41 percent reduction. The infant mortality risk (IMR) due to congenital anomalies fell 31 percent. This is in contrast with the observed 54 percent decline in IMR due to all causes. This reduction in mortality due to congenital anomalies occurred for both whites and blacks in the postneonatal period and for whites only in the neonatal period. Changes ranged from a 1.8 percent increase for the black neonatal mortality risk to a 46.6 percent decrease for the white postneonatal mortality risk. In spite of these relative reductions, the absolute percentage of all infant deaths due to congenital anomalies had increased from 15.8 percent in 1960 to 24.1 percent in 1980. Two categories, cardiovascular and central nervous system anomalies, accounted for 72 percent of infant deaths due to congenital anomalies in 1960 and for 59 percent in 1980; cardiovascular anomalies accounted for 48 percent of all deaths due to congenital anomalies in 1960 and 40 percent in 1980. Infant mortality risks in the United States showed a 2:1 black to white ratio in both 1960 and 1980. However, for infant mortality due to congenital anomalies, the black and white mortality risks were approximately equal in both 1960 and 1980. For infants with birth weights of 500-2,499 g, the risk of neonatal mortality for blacks was less than half the risk for whites.     

Overview of the National Infant Mortality Surveillance (NIMS) project

A slowdown in the decline of infant mortality in the United States and a continuing high risk of death among black infants (twice that of white infants) prompted a consortium of Public Health Service agencies, in collaboration with all states, to develop a national data base of linked birth and infant death certificates for the 1980 birth cohort. This project, referred to as National Infant Mortality Surveillance (NIMS), provides neonatal, postneonatal, and infant mortality risks for blacks, whites, and all races in 12 categories of birthweights. Tabulations were requested for infants born in single and multiple deliveries. For single-delivery births, tabulations included birthweight, age at death, race of infant, and each of these characteristics: infant's live-birth order, sex, gestation, type of delivery, and cause of death; and mother's age, education, prenatal care history, and number of prior fetal losses at greater than or equal to 20 weeks' gestation. An estimated 95% of eligible infant deaths were included in the NIMS tabulations. Analyses have focused on various components of infant mortality, including birthweight distribution of live births, neonatal mortality, and postneonatal mortality. The most important predictor for infant survival is birthweight; survival increases exponentially as birthweight increases to its optimal level. The nearly twofold higher risk of infant mortality among blacks than among whites was related to a higher prevalence of low birthweights, to higher mortality risks in the neonatal period for infants with birthweights of greater than or equal to 3,000 g, and to higher mortality during the postneonatal period for all infants, regardless of birthweight. Moreover, the black-white gap persisted for infants with birthweight of greater than or equal to 2,500 g, regardless of other infant or maternal risk factors.     

Overview of the National Infant Mortality Surveillance (NIMS) project--design, methods, results

The recent slowdown in the decline of infant mortality in the United States and the continued high risk of death among black infants (twice that of white infants) prompted a consortium of Public Health Service agencies to collaborate with all States in the development of a national data base from linked birth and infant death certificates. This National Infant Mortality Surveillance (NIMS) project for the 1980 U.S. birth cohort provides neonatal, postneonatal, and infant mortality risks for blacks, whites, and all races in 12 categories of birth weights. (Note: Neonatal mortality risk = number of deaths to infants less than 28 days of life per 1,000 live births; postneonatal mortality risk = number of deaths to infants 28 days to less than 1 year of life per 1,000 neonatal survivors; and infant mortality risk = number of deaths to infants less than 1 year of life per 1,000 live births.) Separate tabulations were requested for infants born in single and multiple deliveries. For single-delivery births, tabulations included birth weight, age at death, race of infant, and each of these characteristics: infant's live-birth order, sex, gestation, type of delivery, and cause of death; and mother's age, education, prenatal care history, and number of prior fetal losses at 20 weeks' or more gestation. An estimated 95 percent of eligible deaths were included in the NIMS tabulations. The analyses focus on three components of infant mortality: birth weight distribution of live births, neonatal mortality, and postneonatal mortality. The most important predictor for infant survival was birth weight, with an exponential improvement in survival by increasing birth weight to its optimum level. The nearly twofold higher risk of infant mortality among blacks was related to a higher prevalence of low birth weights and to higher mortality risks in the neonatal period for infants weighing 3,000 grams or more, and in the postneonatal period for all infants, regardless of birth weight. Regardless of other infant or maternal risk factors, the black-white gap persisted for infants weighing 2,500 grams or more.     

Infant mortality rate and social disparity at Recife, the metropolis of the North-East of Brazil

We analyzed differences in infant mortality between areas of Recife, a city in the North East of Brazil, analyzing the relationship between living conditions and the risk of death. We compared infant mortality coefficients for 1995 with indicators of living conditions and collected data for the 770 infant deaths and the 27,965 live births. Neighborhoods were ranked according to the quality of living conditions and were grouped into four clusters. The infant, neonatal and postneonatal mortality coefficients were 27.53, 18.84 and 8.69 per 1,000 live births respectively. Lower quality living conditions were associated with higher coefficients. The main causes of infant deaths were perinatal disorders, the coefficient of which was 14.95 per 1,000 live births, followed by congenital malformations, gastroenteritis and bronchopneumonia. With the exception of congenital malformations, the coefficients of all these causes of death increased as living conditions worsened. These inequalities are generally obscured by the presentation of means for the city as a whole.     

Postneonatal mortality among Alaska Native infants - Alaska, 1989-2009

Alaska's postneonatal mortality rate of 3.4 deaths per 1,000 live births during 2006-2008 was 48% higher than the 2007 U.S. rate of 2.3 per 1,000. Among American Indian/Alaska Native (AI/AN) infants, the Alaska rate of 8.0 per 1,000 was 70% higher than the U.S. rate of 4.7. The Alaska Division of Public Health analyzed a linked birth-infant death file for 1989-2009 to examine temporal trends in postneonatal mortality in Alaska, specifically in the Alaska Native (AN) population. Overall and non-Alaska Native (non-AN) rates declined during the entire period, but no significant trends in AN-specific mortality were apparent. Infant mortality review committee findings indicated a decline during 1992-2007 among all postneonatal deaths attributed to sudden infant death syndrome (SIDS) or sudden unexplained infant death (SUID), but not for other causes. Lack of progress in reducing postneonatal mortality, particularly among AN infants, indicates a need for renewed emphasis within the Alaska health-care community. Current initiatives to reduce preventable causes of postneonatal mortality should be evaluated and successful models more widely implemented.     

Congenital malformations as a cause of neonatal and postnatal death in Massachusetts (1970-1980)

Massachusetts birth and death certificate tapes for the years 1970-1980 were linked and analyzed to determine causes of death in the neonatal and postneonatal periods and to identify any related sociodemographic factors. Our analysis suggests that, although the neonatal mortality rate declined by about 43 percent, the postneonatal mortality rate remained relatively unchanged. Perinatal problems remained the principal cause of death during the neonatal period, throughout the decade. In the postneonatal period, congenital malformations became a leading cause of death toward the end of the decade because of a reduction in mortality from infectious diseases and perinatal problems. Infants born to mothers under 18 and over 34 years of age had the highest death rates from congenital birth defects. Higher mortality rates caused by congenital malformations were found in the more industrialized areas of Massachusetts. Further declines in infant mortality rates in Massachusetts will depend on preventive measures to reduce the incidence of congenital malformations.     

Birthweight-specific infant mortality for native Americans compared with whites, six states, 1980.

We used data from the National Infant Mortality Surveillance (NIMS) project to compare birthweights and birthweight-specific mortality risks among Native American and White infants. Because race categories in NIMS were limited to White, Black, and all, we studied six states in which greater than 85 per cent of newborns who were neither White nor Black were Native American. In these states, the infant mortality risk (IMR) among Native Americans was 15.3 deaths per 1,000 live births compared with 8.7 deaths among Whites, relative risk (RR) = 1.8 (95% CI = 1.5-2.0). The percentage of Native American infants with less than 2,500 g birthweights was 5.8 per cent versus 5.0 per cent for White infants. Birthweight-specific neonatal mortality risks were similar for the two race groups, but birthweight-specific postneonatal mortality risks (PNMRs) were more than three times as high among Native Americans compared with Whites for infants of greater than or equal to 2,500 g birthweight. PNMRs were elevated for most causes of death and for all categories for maternal age, educational attainment, trimester prenatal care began, and number of previous live births. Leading causes of postneonatal death among Native Americans of greater than or equal to 2,500 g birthweight were sudden infant death syndrome and infections.     

Birthweight-specific infant mortality risk in cesarean section.

The role of cesarean section in improving infant survival has not been clearly documented. We calculated birthweight- and race-specific infant, neonatal, and postneonatal mortality risks by method of delivery for single- and multiple-delivery infants, using data from 14 states, reported to the Centers for Disease Control through the 1980 National Infant Mortality Surveillance project. For single-delivery infants, the risk of death for infants delivered by cesarean section was 1.6 times higher than for infants delivered vaginally among blacks and 1.2 times higher among whites. The risk was 1.7 times higher during the neonatal period and 1.2 times higher during the postneonatal period. For infants with birthweight less than 1,000 grams, the risk of death was lower when infants were delivered by cesarean section. The risk of death among multiple-delivery infants born by cesarean section was significantly lower than for those born vaginally. This analysis demonstrates that, unlike other birthweight categories, infants with a very low birthweight may have better outcomes if delivered by cesarean section. However, we cannot recommend the routine use of cesarean section for delivering very low birthweight infants. Further studies are needed to determine survival of such infants after controlling for maternal and infant conditions that prompted delivery by cesarean section.     

Mortality patterns among men in the motor vehicle manufacturing industry

This retrospective follow-up study evaluates the mortality experience of 123,232 male hourly workers employed at a motor vehicle manufacturing company in 1973. Company computerized personnel records were used to identify subjects and to obtain their employment history. Follow-up through December 31, 1985 was conducted using company, state, and national data sources. The mortality rates of the cohort were compared with the rates of the United States (U.S.) general population of white or black men, adjusting for age and calendar time, and using the standardized mortality ratio (SMR) as the measure of association. The overall mortality rate of cohort members is lower than the U.S. rate by 11% among whites (11,060 observed/12,427 expected deaths; SMR = 89) and by 24% among blacks (3,744/4,926 deaths; SMR = 76). These low mortality rates reflect deficits of diseases other than cancer. Cancer SMRs are 99 for whites and 90 for blacks. There are slight excesses of stomach cancer (SMR = 113) and of lung cancer (SMR = 108) among whites and of cancer of the large intestine and rectum (SMR = 114) and of the lymphopoietic tissue (SMR = 111) among blacks. Both whites and blacks have a large deficit of buccal cancer and pharynx cancer, and blacks also have a deficit of esophagus cancer. The cohort's overall deficit of deaths is due largely to the favorable mortality experience of active workers. In contrast, white subjects who have left active employment have an 11% mortality excess, and inactive black subjects have a mortality rate that is similar to the general population rate. The increased mortality among inactive whites is not limited to any one particular disease category. This pattern may reflect illness-related employment termination and generalized confounding by socioeconomic status, although the study does not rule out a relationship between workplace exposures and specific diseases. © 1993 Wiley-Liss, Inc.     

Differences in trends of postneonatal mortality by birthweight in upstate New York, 1968-1979.

Postneonatal mortality among neonatal survivors and the distribution of age at death among infant deaths were examined for births occurring in upstate New York, 1968-1979. Postneonatal mortality rates increased among infants weighing 501-1500 grams. Infants weighing 1501-2000 grams experienced an increase in postneonatal mortality during the mid-1970s, later returning to the level of 1968. Among infants 2001+ grams, postneonatal mortality declined throughout the study period. Among all levels of birthweight, the proportion of infant deaths occurring as postneonatal deaths increased.     

The association of maternal smoking with age and cause of infant death

Linked birth certificate and infant death certificate data from Missouri for 1979-1983 were used to explore the association of maternal smoking with age and cause of infant death. The data included 305,730 singleton white livebirths, of which 2,720 resulted in infant deaths. Using multiple logistic regression to control for the confounding effects of maternal age, parity, marital status, and education, the authors found that smoking was associated with both neonatal and post-neonatal mortality and with each cause of death except congenital anomalies. The adjusted odds ratio for smoking was higher for postneonatal deaths than neonatal deaths and was particularly high for two causes: respiratory disease (odds ratio = 3.4) and sudden infant death syndrome (odds ratio = 1.9). A moderate odds ratio (about 1.4) was found for causes attributed to the International Classification of Diseases, 9th Revision Perinatal Conditions Chapter. Although the associations for neonatal deaths and perinatal conditions were partially attributable to the effect of maternal smoking in lowering birth weight, virtually none of the excess respiratory mortality and sudden infant death syndrome mortality among the offspring of smokers was attributable to birth weight differences between the infants of smokers and nonsmokers. This suggests that respiratory deaths and sudden infant death syndrome deaths may be related to the effect of passive exposure of the infant to smoke after birth.     

Postneonatal deaths from infections and injuries: race, maternal risk, and age at death

Most infants with birthweights greater than or equal to 2,500 g who survive the first 27 days of life have a reasonable opportunity to grow into healthy children. However, some of these infants succumb to two potentially preventable causes of death: infections and injuries. Although the relationship between maternal attributes and risk of death from these causes has been described, little is known about how maternal attributes relate to postneonatal age at death. To examine this relationship, we analyzed postneonatal deaths from infections and injuries among 3,116,391 white and 638,915 black neonatal survivors with birthweights greater than or equal to 2,500 g. We grouped postneonates by maternal race and risk status. Infants of mothers greater than or equal to 20 years of age who started prenatal care in the first trimester were considered low risk; all others were high risk. For each category of infection death (respiratory, central nervous system, and other bacterial--including sepsis), neither race nor maternal risk status was related to age at death. The same was true for three categories of injury death (motor vehicle, fire, and homicide), but not for injury deaths in the category of choking, drowning, or suffocation. Among blacks, these deaths occurred at younger ages, regardless of maternal risk status. Thus, efforts to prevent deaths from choking, drowning, or suffocation among blacks should focus on early infancy.     

Disparities in deaths from stroke among persons aged <75 years--United States, 2002

Despite declines in deaths from stroke, stroke remained the third leading cause of death in the United States in 2002, and age-adjusted death rates for stroke remained higher among blacks than whites. In 1997, excess deaths from stroke occurred among persons aged <65 years in most racial/ethnic minority groups, compared with whites. A younger age distribution among Hispanics and other racial/ethnic groups compared with whites might partly explain the disproportionate burden in deaths at younger ages. To examine disparities in stroke mortality among persons aged <75 years, CDC assessed several characteristics of mortality at younger ages by using death certificate data for 2002. This report summarizes the results of that assessment. Overall, 11.9% of all stroke deaths in 2002 occurred among persons aged <65 years; the proportion of stroke decedents who were aged <65 years was higher among blacks, American Indians/Alaska Natives, and Asians/Pacific Islanders, compared with whites. In addition, the mean ages of stroke decedents were statistically significantly lower in these racial groups than among whites. Blacks had more than twice the age-specific death rates from stroke than whites aged <75 years. Approximately 3,400 excess stroke deaths would not have occurred among blacks in 2002 if blacks had had the same death rates for stroke as whites aged <65 years. Moreover, age-adjusted estimates of years of potential life lost (YPLL) before age 75 years from stroke were more than twice as high for blacks than for all other racial groups. Reducing premature death from stroke in these groups will require early prevention, detection, treatment, and control of risk factors for stroke in young and middle-aged adults.     

Deaths: leading causes for 1999.

OBJECTIVES: This report presents final 1999 data on the 10 leading causes of death in the United States by age, race, sex, and Hispanic origin. Leading causes of infant, neonatal, and postneonatal death are also presented. This report supplements the annual report of final mortality statistics and responds to an increasing volume of requests by data users for leading-cause tables with more age and race detail than previously published. METHODS: Data in this report are based on information from all death certificates filed in the 50 States and the District of Columbia in 1999. Causes of death classified by the International Statistical Classification of Diseases and Related Health Problems, Tenth Revision (ICD-10) are ranked according to the number of deaths assigned to rankable causes. Age categories used to present leading causes of death in this report represent a substantial expansion from the age categories previously used to present leading-cause data in the annual report of final mortality statistics. RESULTS: In 1999 the 10 leading causes of death were (in rank order) Diseases of heart; Malignant neoplasms; Cerebrovascular diseases; Chronic lower respiratory diseases; Accidents; Diabetes mellitus; Influenza and pneumonia; Alzheimer's disease; Nephritis, nephrotic syndrome, and nephrosis; and Septicemia and accounted for nearly 80 percent of all deaths occurring in the United States. Differences in the rankings are evident by age, sex, race, and Hispanic origin. Leading causes of infant death for 1999 were (in rank order) Congenital malformations, deformations and chromosomal abnormalities; Disorders related to short gestation and low birthweight, not elsewhere classified; Sudden infant death syndrome; newborn affected by maternal complications of pregnancy; Respiratory distress of newborn; Newborn affected by complications of placenta, cord, and membranes; Accidents; Bacterial sepsis of newborn; Diseases of the circulatory system; and Atelectasis. Important variation in the leading causes of infant death is noted for the neonatal and postneonatal periods.     

The effects of maternal smoking on fetal and infant mortality

Although maternal cigarette smoking has been shown to reduce the birth weight of an infant, previous findings on the relation between smoking and fetal and infant mortality have been inconsistent. This study used the largest data base ever available (360,000 birth, 2,500 fetal death, and 3,800 infant death certificates for Missouri residents during 1979-1983) to assess the impact of smoking on fetal and infant mortality. Multiple logistic regression was used to estimate the joint effects of maternal smoking, age, parity, education, marital status, and race on total mortality (infant plus fetal deaths). Compared with nonsmoking women having their first birth, women who smoked less than one pack of cigarettes per day had a 25% greater risk of mortality, and those who smoked one or more packs per day had a 56% greater risk. Among women having their second or higher birth, smokers experienced 30% greater mortality than nonsmokers, but there was no difference by amount smoked. The prevalence of smoking in this population was 30%. It was estimated that if all pregnant women stopped smoking, the number of fetal and infant deaths would be reduced by approximately 10%. The higher rate of mortality among blacks compared with whites could not be attributed to differences in smoking or the other four maternal characteristics studied. In fact, the black-white difference was greater among low-risk women (e.g., married multiparas aged 20 and over with high education) than among high-risk women (e.g., unmarried teenagers with low education).     

Deaths: leading causes for 2002.

OBJECTIVES: This report presents final 2002 data on the 10 leading causes of death in the United States by age, race, sex, and Hispanic origin. Leading causes of infant, neonatal, and postneonatal death are also presented. This report supplements the annual report of final mortality statistics. METHODS: Data in this report are based on information from all death certificates filed in the 50 States and the District of Columbia in 2002. Causes of death classified by the International Classification of Diseases, Tenth Revision (ICD-10) are ranked according to the number of deaths assigned to rankable causes. RESULTS: In 2002, the 10 leading causes of death were (in rank order) Diseases of heart; Malignant neoplasms; Cerebrovascular diseases; Chronic lower respiratory diseases; Accidents (unintentional injuries); Diabetes mellitus; Influenza and pneumonia; Alzheimer's disease; Nephritis, nephrotic syndrome and nephrosis; and Septicemia and accounted for about 79 percent of all deaths occurring in the United States. Differences in the rankings are evident by age, sex, race, and Hispanic origin. Leading causes of infant death for 2002 were (in rank order) Congenital malformations, deformations and chromosomal abnormalities; Disorders related to short gestation and low birthweight, not elsewhere classified; Sudden infant death syndrome; Newborn affected by maternal complications of pregnancy; Newborn affected by complications of placenta, cord and membranes; Accidents (unintentional injuries); Respiratory distress of newborn; Bacterial sepsis of newborn; Diseases of the circulatory system; and Intrauterine hypoxia and birth asphyxia. Important variation in the leading causes of infant death is noted for the neonatal and postneonatal periods.     

Deaths: leading causes for 2000.

OBJECTIVES: This report presents final 2000 data on the 10 leading causes of death in the United States by age, race, sex, and Hispanic origin. Leading causes of infant, neonatal, and postneonatal death are also presented. This report supplements the annual report of final mortality statistics. METHODS: Data in this report are based on information from all death certificates filed in the 50 States and the District of Columbia in 2000. Causes of death classified by the International Statistical Classification of Diseases and Related Health Problems, Tenth Revision (ICD-10) are ranked according to the number of deaths assigned to rankable causes. RESULTS: In 2000 the 10 leading causes of death were (in rank order) Diseases of heart; Malignant neoplasms; Cerebrovascular diseases; Chronic lower respiratory diseases; Accidents (unintentional injuries); Diabetes mellitus; Influenza and pneumonia; Alzheimer's disease; Nephritis, nephrotic syndrome and nephrosis; and Septicemia and accounted for nearly 80 percent of all deaths occurring in the United States. Differences in the rankings are evidently by age, sex, race, and Hispanic origin. Leading causes of infant death for 2000 were (in rank order) Congenital malformations, deformations and chromosomal abnormalities; Disorders related to short gestation and low birthweight, not elsewhere classified; Sudden infant death syndrome; Newborn affected by maternal complications of pregnancy; Newborn affected by complications of placenta, cord and membranes; Respiratory distress of newborn; Accidents (unintentional injuries); Bacterial sepsis of newborn; Diseases of the circulatory system; and Intrauterine hypoxia and birth asphyxia. Important variation in the leading causes of infant death is noted for the neonatal and postneonatal periods.     

Deaths: leading causes for 2004.

OBJECTIVES: This report presents final 2004 data on the 10 leading causes of death in the United States by age, race, sex, and Hispanic origin. Leading causes of infant, neonatal, and postneonatal death are also presented. This report supplements the annual report of final mortality statistics. METHODS: Data in this report are based on information from all death certificates filed in the 50 states and the District of Columbia in 2004. Causes of death classified by the International Classification of Diseases, Tenth Revision (ICD-10) are ranked according to the number of deaths assigned to rankable causes. RESULTS: In 2004, the 10 leading causes of death were (in rank order) Diseases of heart; Malignant neoplasms; Cerebrovascular diseases; Chronic lower respiratory diseases; Accidents (unintentional injuries); Diabetes mellitus; Alzheimer's disease; Influenza and pneumonia; Nephritis, nephrotic syndrome and nephrosis; and Septicemia and accounted for about 78 percent of all deaths occurring in the United States. Differences in the ranking are evident by age, sex, race, and Hispanic origin. Leading causes of infant death for 2004 were (in rank order) Congenital malformations, deformations and chromosomal abnormalities; Disorders related to short gestation and low birth weight, not elsewhere classified; Sudden infant death syndrome; Newborn affected by maternal complications of pregnancy; Accidents (unintentional injuries); Newborn affected by complications of placenta, cord and membranes; Respiratory distress of newborn; Bacterial sepsis of newborn; Neonatal hemorrhage; and Diseases of the circulatory system. Important variation in the leading causes of infant death is noted for the neonatal and postneonatal periods.     

The effect of air pollution on infant mortality appears specific for respiratory causes in the postneonatal period.

To examine the association between individual lifetime measures of mean exposure to air pollution and postneonatal respiratory deaths, we have conducted a matched population-based case-control study covering all births registered in the Czech Republic from 1989 to 1991 that were linked to death records. For each case of infant death, we have randomly selected 20 controls from infants of the same sex born on the same day and alive when the case died. Exposure was assigned as the arithmetic mean of all 24-hour air pollution measurements in the district of residence of each case and control for the period between the birth and death of the index case. We used conditional logistic regression to estimate the effects of suspended particles, sulfur dioxide, and nitrogen oxides on risk of death in the neonatal and postneonatal period, controlling for maternal socioeconomic status and birth weight, birth length, and gestational age. There were 2,494 infant deaths with exposure data on at least one pollutant, 133 of them from respiratory causes. The effects of all pollutants were strongest in the postneonatal period and were specific for respiratory causes. For these, rate ratios for a 50 microg/m3 increase in particles, sulfur dioxide, and nitrogen oxides were 1.95 [95% confidence interval (CI) = 1.09-3.50], 1.74 (95% CI = 1.01-2.98), and 1.66 (95% CI = 0.98-2.81), respectively, after controlling for all covariates. Only particles showed a consistent association when all pollutants were entered in one model. We found no evidence of a relation between any pollutant and mortality from other causes. These results indicate that the effects of air pollution on infant mortality are specific for respiratory causes in the postneonatal period, are independent of socioeconomic factors, and are not mediated by birth weight or gestational age.