Explaining the 2001-02 infant mortality increase: data from the linked birth/infant death data set.

The U.S. infant mortality rate 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 infant mortality rates increased for very low birthweight infants as well as for preterm and very preterm infants. Although infant mortality rates for very low birthweight infants increased, most of the increase in the infant mortality rate 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 (1 lb 10 1/2 oz). The majority of infants born weighing less than 750 grams die within the first year of life; thus, these births contribute disproportionately to the overall infant mortality rate. Increases in births at less than 750 grams occurred for non-Hispanic white, non-Hispanic black, and Hispanic women. Most of the increase occurred among mothers 20-34 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: first, possible changes in the reporting of births or fetal deaths; second, possible changes in the risk profile of births; and third, possible changes in 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 2001-02 infant mortality increase.     

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.     

The lowest birth-weight infants and the US infant mortality rate: NCHS 1983 linked birth/infant death data.

The National Center for Health Statistics Linked Birth and Infant Death Data Set, 1983 birth cohort, shows that infants weighing less than 750 g, comprising only 0.3% of all births, account for 25% of deaths in the first year of life and for 41% of deaths in the first week. If interventions had prevented the death of these very small babies, the infant mortality rate would have been 8.3 per 1000 live births instead of 10.9, and the Black/White mortality differential would have been reduced by 25%.     

Experiences with linked birth and infant death certificates from the NIMS project

The National Infant Mortality Surveillance (NIMS) project aggregated data provided by 53 vital statistics reporting areas--50 States, New York City, the District of Columbia, and Puerto Rico (subsequently called States)--from their files of linked birth and death certificates and compared individual States' total infant mortality experiences for the 1980 birth cohort by age at death, race, birth weight, and plurality. Therefore, it was essential to achieve maximum uniformity among the separate data sets and to specify when this uniformity could not be obtained. In working with these multiple sources, we identified five key issues that relate to data from linked birth and death certificates: Variations in definitions of variables are often embedded in data that have been gathered from several independent sources. (For NIMS, the sources were 53 reporting areas and the National Center for Health Statistics.) Variations in States' linking procedures--these are based on an individual State's primary purpose for linking the data--affect the completeness and comparability of the 1980 resident birth cohorts used for NIMS. Variations in the recording of some pregnancy outcomes as fetal deaths or live births are known to be a problem in vital statistics data that particularly affects data for events among infants weighing less than 500 g at birth. Ambiguities occur frequently in unknowns or zero values. For NIMS this effect was most pronounced for the pregnancy history variables. Examination of the values reported for unknown or zero categories helps in uncovering problems with and improving quality of data.(ABSTRACT TRUNCATED AT 250 WORDS)     

Racial differences between linked birth and infant death records in Washington State.

The race of infants who died in Washington State 1968-1977 was ascertained by two different methods: 1) race on the death record, and 2) race on the corresponding linked birth record. The second method resulted in substantial increases in the numbers of infant deaths for the nonwhite races: Indian 39 per cent (n = 114/293), Filipino 56 per cent (n = 19/34), Japanese 121 per cent (n = 23/19), and Chinese 117 per cent (n = 14/12). For Indians, the discrepancy between birth and death records was greatest when the age at death was less than seven days (p < 0.01).     

Maternal obesity and risk of infant death based on Florida birth records for 2004

OBJECTIVE: The purpose of this study was to assess the relationship between pre-pregnancy maternal obesity and risk of infant death. METHODS: In March 2004, maternal height and pre-pregnancy weight were added to the data collected on the Florida birth certificate. Using birth records linked to infant deaths, these data were used to assess the relationship between pre-pregnancy maternal obesity, as measured by body mass index, and infant death. RESULTS: Pre-pregnancy maternal obesity was associated with increased odds of infant death. The increased risk was found with and without adjustments for maternal race, marital status, age, education, trimester prenatal care began, first birth, and tobacco use. CONCLUSION: There is a substantial and significant association between pre-pregnancy maternal obesity and infant death.     

Using linked birth and infant death files for program planning and evaluation: NIMS workshop lessons

Health planners should base program decisions on the best information available. Combining information from different sources can be valuable in identifying problems--the essential first step in program planning. To facilitate this process, a workshop was conducted during the National Infant Mortality Surveillance Conference in Atlanta, GA. Maternal and child health directors explored the use of linked birth and infant death data for program planning and evaluation. Linked birth and infant death certificate files permit evaluation of infant mortality by birth weight and other infant and maternal characteristics, thus providing more detailed information than birth or death certificates alone. An assessment of the birth weight distribution of live births, birth weight specific-mortality risks, distribution of deaths by birth weight, and birth weight-specific causes of death can help identify problems in the childbearing population and with the delivery of health services. Once the infant health problems are defined clearly, the selection and delivery of services can be better targeted and evaluated for the reduction of these problems.     

Risk factors for neonatal and post-neonatal mortality in the Central-West region of Brazil: linkage between live birth and infant death data banks

This article focused on risk factors for neonatal and post-neonatal mortality by linking live births and infant death records. The study was conducted in the municipality of Goiania, in the Central-West region of Brazil. A total of 20,981 live births and 342 infant deaths constitute the retrospective cohort. Neonatal and post-neonatal mortality risks were estimated in this cohort study of live births by logistic regression. In the neonatal period, the highest ORs were for delivery in public hospitals (OR = 2.28; 95% CI 1.57-3.32), pre-term neonates (OR = 8.94; 95% CI 5.85-13.67), and low birth weight (OR = 8.92; 95% CI 5.77-13.79). Cesarean delivery appeared as a protective factor (OR = 0.58; 95% CI 0.43-0.78). For post-neonatal mortality, the highest ORs were for illiterate mothers (OR = 6.25; 95% CI 1.25-31.27), low birth weight (OR = 3.12; 95% CI 1.67-5.84), and delivery in public hospitals (OR = 2.65; 95% CI 1. 13-6.23). The linkage identified socioeconomic variables that were more important risk factors for post-neonatal than neonatal mortality.