SPECIAL ARTICLE |
a Division of Vital Statistics, National Center for Health Statistics, Centers for Disease Control and Prevention, Hyattsville, Maryland
b Department of Population and Family Health Sciences, Johns Hopkins Bloomberg School of Public Health, Baltimore, Maryland
| ABSTRACT |
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30 years of age rose in 2005 to levels not seen in almost 40 years. Childbearing by unmarried women also increased to historic record levels for the United States in 2005. The cesarean-delivery rate rose by 4% in 2005 to 30.2% of all births, another record high. The preterm birth rate continued to rise (to 12.7% in 2005), as did the rate for low birth weight births (8.2%). The infant mortality rate was 6.79 infant deaths per 1000 live births in 2004, not statistically different from the rate in 2003. Pronounced differences in infant mortality rates by race and Hispanic origin continue, with non-Hispanic black newborns more than twice as likely as non-Hispanic white and Hispanic infants to die within 1 year of birth. The expectation of life at birth reached a record high in 2004 of 77.8 years for all gender and race groups combined. Death rates in the United States continued to decline, with death rates decreasing for 9 of the 15 leading causes. The crude death rate for children aged 1 to 19 years did not decrease significantly between 2003 and 2004. Of the 10 leading causes of death for 2004 in this age group, only the rates for influenza and pneumonia showed a significant decrease. The death rates increased for intentional self-harm (suicide), whereas rates for other causes did not change significantly for children. A large proportion of childhood deaths continue to occur as a result of preventable injuries.
Key Words: birth death teenage fertility infant mortality low birth weight mortality multiple births cesarean rate vital statistics ICD-10 revised certificates
Abbreviations: NCHSNational Center for Health Statistics IMRinfant mortality rate NMRneonatal mortality rate PNMRpostneonatal mortality rate PMRperinatal mortality rate FMRfetal mortality rate OMBOffice of Management and Budget LBWlow birth weight VLBWvery low birth weight
This annual article is a long-standing feature in Pediatrics. In this article we provide a summary of vital-statistics data through 2005. For birth data, the most current information for 2005 is based on preliminary data, whereas more detailed analyses were based on final data for 2004. For mortality data, the most current data are final 2004 data. We have included a special feature that focuses on the transition to the new birth certificate and related issues for states and the National Center for Health Statistics (NCHS).
| METHODS |
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Current vital-statistics patterns and recent trends through 2004 and 2005 are presented in this report according to age, race, and Hispanic origin as well as other birth and death characteristics. More detailed data are available in the final birth file for 2004 than in the preliminary file for 2005, thus, some of the detailed analyses of birth patterns are not available. Data on infant deaths from the linked birth/infant death data set are final data for 2003. Hispanic origin and race are collected as separate items in vital records. Persons of Hispanic origin may be of any race, although most births and infant deaths of Hispanic origin are to white women. Because there are often important differences in childbearing patterns between non-Hispanic white and Hispanic women, all tables that present data according to race include data separately for non-Hispanic white, non-Hispanic black, and Hispanic women. Data for Native American and Asian or Pacific Islander women are not shown separately according to Hispanic origin, because the vast majority of these women are not Hispanic.
The mother's marital status for birth data, underlying cause of death for deaths, and birth weight for infant deaths have the following special considerations: mothers' marital status was reported directly on the birth certificates or through the electronic birth-registration process in all but 2 states (Michigan and New York) in 2004 and 2005. Details about the reporting of marital status in those 2 states and methods of edits and imputations applied to other items on the birth certificate are presented in NCHS publications.1,3,5
Cause-of-death statistics in this report are based solely on the underlying cause of death, which is compiled in accordance with the International Classification of Diseases, 10th Revision.6 The underlying cause of death is defined as "(a) the disease or injury which initiated the train of morbid events leading directly to death, or (b) the circumstances of the accident or violence which produced the fatal injury."6 Ranking for leading causes of death is based on number of deaths.7
Infant mortality refers to the death of an infant <1 year old. Infant mortality rates (IMRs) were computed by dividing the total number of infant deaths in each calendar year by the total number of live births in the same year. Neonatal mortality rates (NMRs) are shown for infants who died at between 0 and 27 days of age, and postneonatal mortality rates (PNMRs) are shown for infants who died at between 28 days and 1 year of age. Perinatal mortality rates (PMRs) include fetal deaths at
28 weeks of gestation and infant deaths at <7 days of age. Fetal mortality rates (FMRs) are shown for fetal deaths that occurred at
20 weeks of gestation. FMRs and PMRs were computed by dividing the number of fetal or perinatal deaths by the number of live births plus fetal deaths. The IMR, NMR, PNMR, PMR, and FMR are all shown per 1000 live births.
The latest infant mortality statistics according to race and Hispanic origin are from the 2003-period linked birth/infant death data set.8 In this data set, the death certificate was linked with the corresponding birth certificate for each infant who died in the United States in 2003. The purpose of this linkage is to use additional variables available from the birth certificate, such as birth weight, to better interpret infant mortality patterns. Numbers of infant deaths were weighted to compensate for the infant deaths for whom the matching birth certificate could not be identified.8 The weighting procedure results in the same overall IMR as that based on unlinked mortality data; however, small differences may exist because of geographic coverage differences, additional quality control, and weighting.8
Thirteen states (Florida, Idaho, Kansas, Kentucky, Nebraska, New Hampshire, New York [excluding New York City], Pennsylvania, South Carolina, Tennessee, Texas, Vermont [from July 1, 2005], and Washington) used the 2003 revision of the US standard certificate of live birth for data year 2005.3 This article includes 2005 birth data for these 13 states and for the remaining 37 states, New York City, and the District of Columbia, which reported birth data that were based on the 1989 revision of the US standard certificate of live birth. (One state, Vermont, implemented the 2003 revised certificate midyear and reported data for the first half of the year using the 1989 certificate.) The prenatal-care and smoking-during-pregnancy items on the 2003 revision of the US standard certificate of live birth, however, differ from those on the 1989 certificate.9,10 As a result, 2005 data on these items for states that implemented the revised certificates are not compatible with those from the states whose data were compiled with the 1989 revision. Findings are reported separately for these groups.
Eleven states (California, Idaho, Michigan, Montana, New Hampshire, New Jersey, New York [including New York City], Oklahoma, South Dakota, Washington, and Wyoming) used the 2003 revision of the US standard certificate of death by 2004; the remaining 39 states and the District of Columbia collected and reported death data in 2004 on the basis of the 1989 revision of the US standard certificate of death.4 Because the items presented in this report seem largely comparable despite changes to item wording and format in the 2003 revision, data from both groups of states are generally combined.
Births and mortality records that were provided according to reporting areas that used the 2003 revision of the US standard certificate of birth/death (as well as on the unrevised certificates of some additional states) allowed for reporting multiple race categories.14,11,12 To provide uniformity and comparability of the data during the transition period, before all or most of the data would be available in the new multiple-race format, it was necessary to adjust the birth and mortality numerators by "bridging" the responses of those who reported >1 race (multiple race) to a single race.13,14 The bridging procedure used was similar to the procedure used to bridge multiracial population estimates (see discussion on population denominators below).13,14 Multiracial parents and decedents were imputed to a single race (either white, black, American Indian/Alaska native, or Asian/Pacific Islander) according to the combination of races, Hispanic origin, gender, and age indicated on the birth or death certificate.
Population denominators for the calculation of birth, death, and fertility rates are estimates that were based on the population enumerated by the US Census Bureau as of April 1, 2000. Estimates for 20002005 and the revised estimates for the intercensal period of 19911999 were produced under a collaborative arrangement between the US Census Bureau and the NCHS. Reflecting the new guidelines issued in 1997 by the Office of Management and Budget (OMB), the 2000 census included an option for individuals to report >1 race as appropriate for themselves and household members.11 The 1997 OMB guidelines also provided for the reporting of Asian persons separately from native Hawaiians or other Pacific Islanders. Under the previous OMB standards issued in 1977, data for Asian or Pacific Islander persons were collected as a single group.12 Birth and death certificates for most states currently collect only 1 race for mother and decedent in the same categories as specified in the 1977 OMB guidelines and do not report Asians separately from native Hawaiians or other Pacific Islanders. Thus, birth and death certificate data by race (the numerators for birth and death rates) are currently incompatible with the population data collected in the 2000 census (the denominators for the rates).
To produce birth and death rates for 20002005 and revised intercensal rates for the 19911999 period, it was necessary to bridge the reported population data for multiple-race persons back to single-race categories. In addition, the 2000 census counts were modified to be consistent with the 1977 OMB race categories, that is, to report the data for Asians and native Hawaiians or other Pacific Islanders as a combined category of Asian or Pacific Islanders.13 The procedures used to produce the bridged populations have been described in separate publications.1315 As national vital-statistics data based on the 1997 OMB guidelines become available, the use of bridged populations can be discontinued.
Data for the international comparisons of births, birth rates, and IMRs were obtained from the 2003 United Nations Demographic Yearbook.16
| NATURAL INCREASE |
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| BIRTHS |
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Racial and Ethnic Composition
Fertility rates vary among race and ethnic groups (Table 2). In 2005, Hispanic women had the highest fertility rate (99.1 births per 1000 women aged 1544 years in preliminary 2005 data) and non-Hispanic white women had the lowest fertility rate (58.4).3 The rate rose between 2004 and 2005 for Hispanic and American Indian women, declined slightly for Asian and Pacific Islander women, and was essentially unchanged for non-Hispanic white and non-Hispanic black women. In 2005, 23.9% of all births in the United States were to Hispanic women, compared with 15% in 1990.1,3
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20 Years Old
Birth rates for women aged
30 years have generally increased over the past 2 decades.18 Between 2004 and 2005, the birth rate for women aged 30 to 34 years rose slightly to 95.9 births per 1000, the highest rate since 1964. The rate for women 35 to 39 years of age rose to 46.3 births per 1000, 2% over the rate in 2004 and the highest rate since 1965.3 The birth rate for women aged 40 to 44 years also rose by 2% to 9.1, the highest rate since 1968, and the rate for women 45 to 49 years of age increased slightly to 0.6 births per 1000 women, the first increase in the rate since 2000 and the highest rate since 1970.1,3,5,18
Unmarried Mothers
The total number of births to unmarried women rose by 4% to 1525345 in 2005 (preliminary data), compared with 1470189 in 2004.1,3,19 During the period 20022005, the number of births to unmarried women increased 12% overall. The birth rate for unmarried women increased 3% in 2005 to 47.6 per 1000 unmarried women aged 15 to 44 years, up from 46.1 in 2004. In 2005, the proportion of births to unmarried women increased to 36.8%, compared with 35.8% in 2004 (Table 4). The proportions increased for all population groups by race and Hispanic origin.
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For the 7 states for which data on smoking are available from the 2003 revision for all of 2004 (Table 5), the overall smoking rate was 16.3%; the revised question on smoking differs considerably from the question on the 1989 certificate, and it is expected that the revised question will elicit higher rates of smoking during pregnancy. The new question on maternal smoking should provide higher-quality, more-reliable information because women are afforded the chance to report that their smoking behavior has changed.1
Prenatal Care
This report includes data on the timing of prenatal care based on both the 1989 and the 2003 revisions to the US standard certificate of live birth. The 2003 revision of the birth certificate introduced substantive changes in item wording and also to the sources of prenatal information. Accordingly, prenatal-care data for the 2 revisions are not directly comparable and are shown separately.1 Data from the 1989 certificate are available for 41 states, New York City, and the District of Columbia. Data from the 2003 revision are available for 7 states (New York State excludes New York City). Some states used both certificates in 2004 and are not included in this analysis.
Timely initiation of prenatal care does not seem to have improved in the United States in 2004 (Table 5). On the basis of the reporting area of 41 states, New York City, and the District of Columbia for which comparable data using the 1989 certificate are available, 83.9% of mothers were reported to have begun care within the first 3 months of pregnancy, a level not significantly different from that reported for the same reporting area for 2003.1 Levels of prenatal care in the first trimester rose slowly but steadily between 1990 and 2003. No change was observed in the percentage of women receiving late (care beginning in the third trimester of pregnancy) or no care between 2003 and 2004 (3.6%). Appropriate prenatal care can enhance pregnancy outcome by assessing risk, providing health care advice, and managing chronic and pregnancy-related health conditions.2527
The percentage of women beginning care in the first trimester of pregnancy was essentially unchanged among the racial and Hispanic-origin groups in the 41-state reporting area between 2003 and 2004. Although large differences persist, efforts to reduce racial disparities in the timely receipt of prenatal care have met with some success. From 1990 to 2003, first-trimester care increased by 7% for non-Hispanic white women, 24% for non-Hispanic black women, and 29% for Hispanic women.
For the 7 revised states for which data from the 2003 revision are available for all of 2004, 72.9% of women were reported to have begun care in the first 3 months of pregnancy; 6.2% of mothers were reported to have late or no prenatal care (Table 5). As noted above, the revised prenatal-care item is substantively different from the unrevised question; levels of prenatal-care utilization based on revised data are substantially lower than those based on unrevised data.
Cesarean Delivery
In 2005, the preliminary rate of cesarean delivery rose 4% to 30.2% of all births, another record high for the United States (Table 4).1,3,28 The cesarean rate declined somewhat during the early and mid-1990s but has risen 46% since 1996 (20.7). Rates increased between 2004 and 2005 for non-Hispanic white, non-Hispanic black, American Indian, Asian or Pacific Islander, and Hispanic women, as well as for each 5-year age group (Table 4). Since 1996, rates have risen by >40% for all age groups, including for young women <20 years of age (Fig 2).
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Multiple Births
The twin birth rate rose by 2% in 2004 to 32.2 twins per 1000 total births, a record high (Table 4). The twinning rate has climbed 42% since 1990 (22.6) and 70% since 1980 (18.9).1,33 In contrast, the rate of triplet and higher-order multiple births (triplet+) declined by 6% in 2004 to 176.9 per 100 000. The triplet and higher-order multiple-birth rate soared by >400% between 1980 and 1998; since 1999, however, this rate has been comparatively stable, trending slightly downward. The current-year level is 9% lower than the 1998 peak.1,33 Twinning rates increased in 2004 for non-Hispanic white (36.3 in 2004) and non-Hispanic black (35.6) women. Triplet and higher-order multiple births declined among non-Hispanic white (243.4 per 100000 for 2004) and non-Hispanic black (99.7) women.
Despite the recent small amelioration in triplet+ birth rates, levels remain fourfold higher than those observed before the introduction of fertility therapies in the early 1980s. The rising incidence of multiple births over the last 2 decades, especially that for higher-order multiples, has been associated with 2 related trends: the older age at childbearing and the increasing use of fertility therapies, which include ovulation-inducing drugs and assisted reproductive technologies.3438 The recent interruption in the upsurge of triplet+ births may be related, in part, to recommendations in the late 1990s (further refined in 2004) from the American Society of Reproductive Medicine, which was intended to prevent higher-order multiple pregnancies by limiting the number of embryos transferred.39,40 A shift from the transfer of 3 embryos (a predictor of triplet and higher-order multiple deliveries) to 2 embryos seems to have occurred between the mid- to late 1990s and 2002 (the most recent year for which data are available).34,41 Other factors also may have influenced the recent change in triplet and other higher-order multiple-birth rates.42,43
Preterm Birth
The percentage of births that were preterm (<37 completed weeks of gestation) rose from 12.5% to 12.7% from 2004 to 2005 (Fig 3 and Table 4). The percentage of infants delivered preterm has risen 20% since 1990 (10.6%). Preterm rates rose significantly for non-Hispanic white (11.7% for 2005), non-Hispanic black (18.4%), and Hispanic (12.1%) infants between 2004 and 2005. Rates for non-Hispanic white and Hispanic births have been rising for more than a decade, increasing 38% for non-Hispanic white and 10% for Hispanic infants since 1990. The preterm rate for black infants declined modestly during the 1990s but has been on the rise since the year 2000. Preterm infants have higher mortality rates when compared with term infants.8 Although the upswing in multiple births has had an important influence on recent trends in preterm birth rates, shorter gestations have also risen among singleton deliveries. The causes of preterm delivery are not fully understood, and until progress is made in this regard, substantial reduction in the preterm birth rate seems unlikely.1,3,44,45
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LBW
The percentage of infants born LBW (births weighing <2500 g) increased in 2005 to 8.2% of all births from 8.1% in 2004 (Table 4). The percentage of infants born LBW has increased >20% since the mid-1980s (6.7 in 1984); the current level is the highest level reported since 1968.1,3 LBW rates rose 1% to 2% for non-Hispanic white, non-Hispanic black, and Hispanic infants between 2004 and 2005. Among all births, levels of both very low birth weight (VLBW; births weighing < 1500 g), and moderately LBW (births weighing 15002499 g) increased slightly for 2005 (see Table 4). LBW and especially VLBW are major predictors of infant morbidity and mortality. The risk of early death for infants born at moderately LBW (15002499 g) is 5 times higher than that of heavier infants; the risk for VLBW infants is >100 times that of infants born at
2500 g.8
| INFANT MORTALITY |
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Perinatal and Fetal Mortality
The PMR declined 2% between 2002 and 2003 from 6.91 to 6.74 per 1000 live births and fetal deaths (Fig 4). The PMR is defined as late fetal (
28 weeks of gestation) and early neonatal (<7 days) deaths per 1000 births plus fetal deaths. The PMR has been declining fairly consistently for more than half a century.47 The decrease in the PMR for 20022003 is attributable largely to the sizable drop in late fetal deaths (from 3.19 to 3.04 per 1000); only a small decline in early neonatal mortality was observed (from 3.73 to 3.70 per 1000 for 20022003).
The 2003 FMR (fetal deaths of at least 20 weeks of gestation) was 6.23 per 1000 live births plus fetal deaths, down from 6.41 in 2002. The late FMR declined 5%; the early FMR (fetal deaths of 2027 weeks) decreased very slightly from 3.24 to 3.21 between 2002 and 2003. The overall FMR has declined substantially over the last 50 years and is down 17% since 1990.48 The decline over this period has been almost exclusively among late fetal deaths (down 29% for 1990 and 2003); the early FMR has not improved over this period.48
Geographic Variation
Table 6 presents information on state variations in preterm birth and LBW for 2004 (latest year for which final state data are available). When examining preterm births according to state, >15% of all infants in Alabama, Louisiana, Mississippi, and South Carolina (15.5%17.9%) were born preterm, compared with
10.1% of infants in Connecticut, New Hampshire, Oregon, and Vermont (8.3%10.1%). For 2004, >10% of all infants in Alabama, Louisiana, Mississippi, South Carolina, and the District of Columbia were born at LBW (10.2%11.6%), compared with <6.5% of infants in Alaska, Maine, Oregon, Vermont, and Washington (6.0%6.4%). Variations by state in preterm births and LBW reflect compositional differences by race, ethnicity, and socioeconomic status in the population in addition to other factors (eg, incidence of multiple birth) that are associated with preterm or LBW births.
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The rank order of leading causes of death can vary according to race or Hispanic origin. For example, in 2003, as in earlier years, LBW (not congenital malformations) was the leading cause of death among non-Hispanic black and Puerto Rican infants.8
| INTERNATIONAL COMPARISONS |
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40% of the other countries listed in Table 7. Only 4 countries, Portugal, Greece, Israel, and New Zealand, experienced a distinctive decline in the IMR between 2002 and 2003, although the rate for Israel was similar in 2001 and 2003.
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| DEATHS |
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Expectation of Life
The estimated expectation of life at birth for a given year represents the average number of years that a group of infants would be expected to live if, throughout their lifetime, they were to experience the age-specific death rates prevailing during the year of their birth. In 2004, the expectation of life at birth reached a record high of 77.8 years, an increase of 0.3 years from the previous year.2,4 Life expectancy increased from the previous year by 0.5 years for black males, 0.4 years for white males, 0.3 years for white females, and 0.2 years for black females, setting record highs for the 4 groups. In 2004, life expectancy at birth was 80.8 years for white females, 76.3 years for black females, 75.7 years for white males, and 69.5 years for black males.
Causes of Death
The 15 leading causes of death in 2004 (final data) accounted for >80% of all US deaths (Table 8). Between 2003 and 2004, age-adjusted death rates declined significantly for 9 of the 15 leading causes of death, as follows: heart disease by 6.6%, cancer by 2.3%, cerebrovascular diseases (stroke) by 6.5%, chronic lower respiratory diseases by 5.1%, diabetes mellitus (diabetes) by 3.2%, influenza and pneumonia by 10.0%, nephritis, nephritic syndrome, and nephrosis (kidney disease) by 1.4%, septicemia by 3.4%, and chronic liver disease and cirrhosis by 3.2%. Although there were declines in the death rates for homicide and Parkinson's disease, these declines were not statistically significant.4 Among the 13 leading causes of death in 2004, age-adjusted death rates increased for essential (primary) hypertension and hypertensive renal disease (hypertension) by 4.1%, Alzheimer disease by 1.9%, and unintentional injuries by 1.1%. Alzheimer disease moved from eighth to seventh place in the leading-cause list.
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| THE TRANSFORMATION OF VITAL STATISTICS: IMPLICATIONS FOR THE AVAILABILITY OF PERINATAL DATA |
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Delayed Release of Birth, Fetal Death, and Linked Birth/Infant Death Data
Beginning with data year 2003, in which 2 states implemented the new birth certificate, the NCHS began accommodating data from the 57 independent reporting areas on the basis of both the 2003 US standard certificate of live birth (revised) and the 1989 US standard certificate of live birth (unrevised).57 For 2004, the number of states using the 2003 revision increased to 9, with 2 states revising during the year (ie, these states provided a combination of revised and unrevised data; Fig 5). 1 For 2005, a total of 13 states provided data from the 2003 revision for the full year, with 1 revised during 2005.3 Another complication is that multiple race of mother and father is on a different track. For 2003, 6 states provided multiple-race data (1 state provided these data for December only).57 In 2004, the number of states increased to a total of 15 and rose again in 2005 to 19 (1 state provided 2005 multiple-race data for selected facilities only).1,3 Implementation of the revised fetal death reports is on a similar but somewhat slower track than that of birth.
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Lack of National Data for Key Items
The revised birth certificate and fetal death report include important modifications to wording and/or sources for several key items that are traditionally presented in this article: educational attainment, maternal tobacco use, and prenatal care. Although collected on both the revised and unrevised certificates, data on these items are not considered comparable between revisions. As a result, national data on these items will not be available for several years, which limits our ability to describe trends, patterns, and potential associations.
| ACKNOWLEDGMENTS |
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| FOOTNOTES |
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Address correspondence to Brady E. Hamilton, PhD, National Center for Health Statistics, Centers for Disease Control and Prevention, 3311 Toledo Rd, Room 7416, Hyattsville, MD 20782. E-mail: bhamilton{at}cdc.gov
The authors have indicated they have no financial relationships relevant to this article to disclose.
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