Changes in the black-white infant mortality gap from 1983 to 1991 in the United States

Background: The long-standing difference in infant mortality in the United States between black and white infants has increased in recent years. To help identify the cause, we evaluated changes in birthweight distributions (BDs) and birthweight-specific mortality rates (BSMRs) among black and white infants born in the United States between 1983 and 1991.Methods: Using national linked birth and death certificate data, we limited analyses to singleton births that occurred in the United States to resident, non-Hispanic black and white women. Birthweight data were analyzed in 500 g increments. The black-white gap was partitioned into deaths due to differences in BDs and BSMRs.Results: The black-white infant mortality rate ratio increased from 2.1 in 1983 to 2.4 in 1991. Decreases in BSMRs among infants weighing from 500 to 2499 g occurred in both groups but were smaller among black than white infants; consequently, the percentage of excess deaths to black infants due to differences in BSMRs almost doubled during the study period, from 6.5% to 11.9%. Rates of very low birthweight (VLBW, <1,500 g) increased for black infants, but the BD for white infants changed little. Although about 90% of the excess deaths to black infants resulted from differences in BDs, the changes in BDs had a minimal effect on the widening infant mortality gap.Conclusions: A significant reduction in the black-white infant mortality gap will require a reduction in VLBW and low birthweight (LBW, <2,500 g). To keep the gap from growing, we must also investigate why decreases in BSMRs were smaller among black than white infants between 1983 and 1991.     

Infant mortality and low birth weight among black and white infants--United States, 1980-2000

Despite substantial reductions in U.S. infant mortality during the past several decades, black-white disparities in infant mortality rates persist. One of the Healthy People 2010 national objectives for maternal and infant health is to reduce deaths among infants aged < 1 year to < or = 4.5 per 1,000 live births among all racial/ethnic groups (objective 16-1c). Important determinants of racial/ethnic differences in infant mortality are low birth weight (LBW), defined as < 2500 grams, and very low birth weight (VLBW), defined as < 1500 grams. High birth weight-specific mortality rates (BWSMRs) occur at these low birth weights. Healthy People 2010 goals include reducing LBW to 5% and VLBW to 0.9% of live births (objectives 16-10a and 16-10b, respectively). To assess progress toward meeting these national objectives, CDC analyzed birth and death certificate data from the National Center for Health Statistics. This report describes trends in mortality and birth weight among black and white infants, which indicate persistent black-white disparities and underscore the need for prevention strategies that reduce preterm delivery and specific medical conditions that lead to infant death.     

Surveillance of postneonatal mortality, United States, 1980-1987

In the United States, one-third of all infant deaths (deaths of infants ages 0-364 days) occurs in the postneonatal period (28-364 days). A substantial proportion of these deaths potentially could be prevented. To examine recent trends in postneonatal mortality (PNM) in the United States, the investigators analyzed birth and death certificate data for resident infants for the period from 1980 through 1987. Rates of PNM declined 11% from 3.5 to 3.1/1,000 live births among white infants and declined 16% from 7.3 to 6.1/1,000 live births among black infants. Most of the decline resulted from reduced mortality from infectious diseases and injuries. A decreased mortality attributable to sudden infant death syndrome (SIDS) among black infants additionally accounted for the decline. Autopsy rates for SIDS increased from 82% to 92% but did not differ for black infants and white infants. Birth defects-related PNM declined more among white infants than among black infants. The racial gap in PNM (rate ratio (RR) = approximately 2.0) persisted. However, the largest black/white gap occurred in the Northeast (RR = 2.5), the region with the lowest PNM. Black infants were 2.7 and 2.3 times more likely to die of infections and injuries, respectively, than were white infants. Although PNM rates declined during the 1980s, a greater rate of reduction is needed to achieve the Year 2000 objectives, especially among black infants. Such reductions are possible through improved access to comprehensive pediatric care as well as education and community-oriented prevention programs designed to reduce deaths due to infections and injuries. A better understanding of the etiology of SIDS and birth defects is critical for preventing postneonatal deaths.     

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.     

Explaining the 2001-2002 infant mortality increase in the United States: data from the linked birth/infant death data set.

The U.S. infant mortality rate (IMR) increased from 6.8 infant deaths per 1,000 live births in 2001 to 7.0 in 2002, the first increase in more than 40 years. From 2001 to 2002, IMR increased for very low birthweight infants as well as for preterm and very preterm infants. Although IMR for very low birthweight infants increased, most of the increase in IMR from 2001 to 2002 was due to a change in the distribution of births by birthweight and, more specifically, to an increase in infants born weighing less than 750 grams. The majority of infants born at less than 750 grams die within the first year of life; thus, these births contribute disproportionately to overall IMR. Increases in births at less than 750 grams occurred fornon-Hispanic white, non-Hispanic black, and Hispanic women. Most of the increase occurred among mothers 20 to 34 years of age. Although multiple births contributed disproportionately, most of the increase in births at less than 750 grams occurred among singletons. Three hypotheses were evaluated to assess their possible impact on the increase in less than 750-gram births: possible changes in (1) the reporting of births or fetal deaths, (2) the risk profile of births, and (3) medical management of pregnancy. Although each of these factors may have contributed to the increase, the relative effects of these and other factors remain unclear. More detailed studies are needed to further explain the 2001-2002 infant mortality increase.     

Racial/ethnic disparities in infant mortality--United States, 1995-2002

A national health objective for the year 2000 was to reduce the infant mortality rate (IMR) in the United States to 7.0 deaths per 1,000 live births among infants aged <1 year. The national health objective for 2010 targets a rate of 4.5 infant deaths per 1,000 live births; an overarching goal calls for eliminating disparities among racial and ethnic populations. To examine racial and ethnic disparities in IMRs, data were analyzed from the National Vital Statistics System for the period 1995-2002. IMRs were calculated by race/ethnicity of the mother in each of the 50 states and the District of Columbia (DC). During 1995-2002, the overall IMR in the United States declined from 7.6 infant deaths per 1,000 live births in 1995 to 6.8 in 2001, and then increased to 7.0 in 2002. On the basis of data for 1995-2002 combined, the target of 4.5 infant deaths per 1,000 live births had been achieved by few racial/ethnic populations in few states. To reach the target in all racial/ethnic populations, strategies should identify and address those factors that contribute to high IMRs and disparities among populations.     

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.     

Neonatal intensive-care unit admission of infants with very low birth weight --- 19 States, 2006

Neonatal mortality is disproportionately common among infants with very low birth weight (VLBW) (<1,500 g [3.3 lbs]). In 2006, the mortality rate among infants with VLBW was 240.4 per 1,000 live births. Because neonatal intensive care has been shown to reduce mortality among infants with VLBW, current standards call for neonatal intensive-care for all infants with VLBW; however, the proportion of infants with VLBW who are admitted to a neonatal intensive care unit (NICU) is not known, nor are the predictors for NICU admission. To estimate the prevalence of admission to NICUs among infants with VLBW and assess factors predicting admission, CDC analyzed birth data from 2006 for 19 states. This report summarizes the results of that analysis, which found that overall, 77.3% of infants with VLBW were admitted to NICUs (range: 63.7% in California to 93.4% in North Dakota). Among infants with VLBW born to Hispanic mothers, 71.8% were admitted to NICUs, compared with 79.5% of those with non-Hispanic black mothers and 80.5% of those with non-Hispanic white mothers. Multivariate analysis of the data indicated that preterm delivery, multiple births, and cesarean delivery all were independently associated with greater prevalence of NICU admission among infants with VLBW. Wide variation was observed among states in the prevalence of NICU admission of infants with VLBW; these state data should be assessed further, and barriers to NICU admission should be identified and addressed.     

Changing patterns of low birthweight and preterm birth in the United States, 1981-98

Low birthweight (LBW) and preterm birth are primary risk factors for infant morbidity and mortality in the US. With increasing multiple births and delayed childbearing, it is important to examine the separate contributions of these characteristics to the increases in LBW and preterm birth rates. US natality records from 1981, 1990 and 1998 were used to calculate LBW (% births <1500, 1500-2499, <2500 g) and preterm (% births <29, 29-32, 33-36, <37 weeks gestation) rates. Data were stratified by maternal race (black or white) and plurality (singleton vs. multiple birth). LBW and preterm rates among singletons were adjusted for maternal age to examine the influence of demographic shifts on LBW trends. From 1981 to 1998, LBW increased 12% among white infants, but remained relatively stable among black infants. During the same time, preterm birth increased 23% among white infants compared with 3% among black infants. For both black and white infants, the increase in LBW and preterm births was greater among multiple births than among singletons. Adjustment for maternal age did not reduce the temporal increase in LBW or preterm birth among singletons. Black infants continue to experience a markedly higher incidence of LBW and preterm birth, but the racial gap in these outcomes has narrowed slightly in recent years as a result of increasing LBW and preterm birth among white births. The differing trends for white and black infants are the consequence of a disparate trend in the incidence and outcome of multiple births coupled with increases in LBW and preterm birth among white singletons. Understanding the differential patterns in birth outcomes among white and black infants is necessary to develop effective interventions designed to decrease racial disparities in pregnancy outcome.     

Regional differences in birth weight-specific infant mortality, United States, 1980

To describe regional differences in birth weight-specific infant mortality in the United States, we used data from the National Infant Mortality Surveillance project. The infant mortality risk (IMR) for the nation was 11.0 deaths per 1,000 live births. The risk (with 95 percent confidence intervals [CI]) for the four U.S. Census regions were West 9.9 (9.7 to 10.1), Northeast 10.4 (10.1 to 10.6), North Central 10.8 (10.6 to 11.0), and South 12.1 (11.9 to 12.3). In all regions, the IMR for blacks was approximately twice that of whites. Seventy-two percent of the higher IMR in the South was due to a higher proportion of black births compared with the remainder of the nation, reflecting the higher mortality rates suffered by black infants, and 28 percent to higher mortality among southern whites. The IMR for whites in the South was significantly higher than in the remainder of the nation: 9.8 versus 9.1 (relative risk = 1.09, CI = 1.06 to 1.11). Thirty-six percent of this excess in IMR was due to a higher frequency of low birth weight (less than 2,500 grams), 18 percent was due to higher IMR in infants with birth weight less than 2,500 grams, and 46 percent due to higher IMR in infants with birth weights of 2,500 g or more. Black infants born in the West had a lower risk of death than black infants in the other regions.(ABSTRACT TRUNCATED AT 250 WORDS)     

Trends in preterm-related infant mortality by race and ethnicity, United States, 1999-2004.

Trends in preterm-related causes of death were examined by maternal race and ethnicity. A grouping of preterm-related causes of infant death was created by identifying causes that were a direct cause or consequence of preterm birth. Cause-of-death categories were considered to be preterm-related when 75 percent or more of total infant deaths attributed to that cause were deaths of infants born preterm, and the cause was considered to be a direct consequence of preterm birth based on a clinical evaluation and review of the literature. In 2004, 36.5 percent of all infant deaths in the United States were preterm-related, up from 35.4 percent in 1999. The preterm-related infant mortality rate for non-Hispanic black mothers was 3.5 times higher and the rate for Puerto Rican mothers was 75 percent higher than for non-Hispanic white mothers. The preterm-related infant mortality rate for non-Hispanic black mothers was higher than the total infant mortality rate for non-Hispanic white, Mexican, and Asian or Pacific Islander mothers. The leveling off of the U.S. infant mortality decline since 2000 has been attributed in part to an increase in preterm and low-birthweight births. Continued tracking of preterm-related causes of infant death will improve our understanding of trends in infant mortality in the United States.     

Cause-Specific Trends in Neonatal Mortality Among Black and White Infants,United States, 1980–1995

Objective: Although neonatal mortality has been declining more rapidly than postneonatal mortality in recent decades, neonatal mortality continues to account for close to two-thirds of all infant deaths. This report uses U.S. vital statistics data to describe national trends in the major causes of neonatal mortality among black and white infants from 1980 to 1995. Methods: Mortality rates were estimated as the number of deaths due to each cause (based on International Classification of Diseases, 9th Revision, codes) divided by the number of live births during the same time period. Linear regression models and smoothed rates were used to describe trends. Results: During the study period, neonatal mortality declined 4.0% per year for white infants and 2.2% per year for black infants, and the black–white gap increased from 2.0 to 2.4. By 1995, disorders relating to short gestation and low birth weight were the number one cause of neonatal death for black infants and the number two cause for white infants, had the highest black–white disparity (4.6, up from 3.3 in 1980), and accounted for almost 40% of excess deaths to black infants (up from 24% in 1980). Congenital anomalies were the number two cause of neonatal death for black infants and the highest ranked cause for white infants in 1995, and it is the only cause for which there was not a substantial excess risk to black infants. Conclusions: Large declines in neonatal mortality have been achieved in recent years, but not in the black–white gap, which has increased. Declines were slower for black than white infants overall and for almost all causes. Prevention of preterm delivery and low birth weight continue to be a priority for reducing neonatal mortality, particularly among black infants. Although congenital anomalies do not contribute substantially to the black–white gap, their diagnosis, treatment, and prevention is critical to reducing overall neonatal mortality.     

Rising Infant Mortality in Delaware: An Examination of Racial Differences in Secular Trends

Objectives: Recent increases in the Delaware Infant Mortality Rate (IMR) have been attributed to a rise in the mortality of very low birth weight (VLBW, <1500 g) infants born to mothers of higher socioeconomic status. This study examines whether the determinants of infant mortality trends in Delaware vary by race. Methods: Linked birth/infant death cohort files for the two periods 1993–1997 and 1998–2002 were used to evaluate the determinants of infant mortality trends separately for White and Black racial groups. Kitagawa analyses determined the components of race-specific infant mortality trends attributable to changes in both the birthweight distribution and birthweight-specific mortality rates. Maternal characteristics were examined to identify factors associated with IMR changes. Results: Between the two time periods, infant mortality increased 23% among White infants and 17% among Black infants. For both races, the infant mortality increase was explained by increases in the incidence and mortality of VLBW infants, specifically below <500 grams for Blacks and <1,000 grams for Whites. The increased incidence of VLBW deliveries was statistically significant only among Whites, almost 40% of which was explained by an increase in multiple births. For both Whites and Blacks, the increase in VLBW mortality occurred mainly among births to more traditionally advantaged women who were twenty or older, at least high school educated, married, privately insured, had received first trimester prenatal care, and those who delivered multiple births. Conclusions: These findings suggest that conventional strategies of increasing access to prenatal care among disadvantaged women may be insufficient to reverse recent IMR increases in Delaware, irrespective of race. Future efforts should focus on understanding the causes of the increased infant mortality associated with higher socioeconomic status, including changes in assisted reproductive technology utilization, maternal health status, and obstetric practice.     

2012—2018年柳州市婴儿死亡率变化趋势分析

目的 分析2012—2018年柳州市婴儿死亡率（IMR）水平与变化趋势,为制定防控婴儿死亡的政策和措施提供参考依据。 方法 对柳州市妇幼卫生信息管理系统收集的2012—2018年柳州市394 476例出生信息和1 726例婴儿死亡信息进行分析。采用趋势χ2检验分析IMR及主要死因别死亡率的变化趋势。 结果 2012—2018年柳州市IMR从5.95‰下降至3.17‰（χ2 = 86.967,P＜0.001）。苗族（9.26‰）、侗族（7.82‰）和瑶族（6.76‰）母亲IMR高于汉族（3.33‰）和壮族（3.83‰）。IMR与母亲年龄呈U型曲线,20岁以下组最高（9.03‰）。IMR随母亲文化程度增加而下降,小学及以下文化组最高（10.48‰）。早期早产儿IMR（162.11‰）是足月儿（2.86‰）的56.68倍,极低出生体重儿IMR（170.06‰）是出生体重2 500g及以上（2.68‰）的63.46倍。婴儿死亡的前5种死因依次为早产或低出生体重、肺炎、出生窒息、意外窒息、先天性心脏病,占婴儿死亡的67.32%。 结论 2012—2018年柳州市IMR呈下降趋势,不同母婴特征的IMR存在差异。应根据IMR的潜在风险因素与人群分布制定针对性的干预措施。     

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.