Matern Child Health J (2011) 15:1135–1142 DOI 10.1007/s10995-010-0665-9

Racial and Ethnic Variations in Temporal Changes in Fetal Deaths and First Day Infant Deaths Martha S. Wingate • Wanda D. Barfield

Published online: 26 August 2010 Ó Springer Science+Business Media, LLC 2010

Abstract The purpose was to examine changes in overall and gestational age-specific proportions and rates of fetal death, first day death (\24 h), and combined fetal-first day death from 1990–1991 to 2001–2002. Changes were considered by race/ethnicity. Deliveries to U.S. white, black, and Hispanic mothers were selected from the NCHS linked live birth-infant death cohort and fetal deaths files (1990–1991 and 2001–2002). There was an overall improvement in mortality, but improvements were not uniform across all racial/ ethnic groups or by gestational age. The fetal mortality rate among whites and Hispanics declined 4.32 and 12.82 percent, respectively. For blacks, the fetal mortality rate increased 4.06 percent between 1990–1991 and 2001–2002. Despite overall reductions in perinatal and\24 h mortality, black rates in all outcomes maintained a twofold disparity. The overall black: white fetal mortality rate ratio increased from 2.17 to 2.36 over time. The gestational age-specific black: white combined fetal-first day mortality rate ratios were greater than 1 at later gestational ages. In some cases, the ratio increased over time, indicating that despite reductions, fetal mortality did not decline uniformly among whites and blacks at term and post-term. Despite overall improvements in fetal, first day, and combined fetal-first day

M. S. Wingate (&) Department of Health Care Organization and Policy, School of Public Health, University of Alabama at Birmingham, RPHB 330, 1530 3rd Avenue South, Birmingham, AL 35294-0022, USA e-mail: [email protected] W. D. Barfield Division of Reproductive Health, Centers for Disease Control and Prevention, 4770 Buford Highway, MS-K-22, Atlanta, GA 30341, USA e-mail: [email protected]

mortality, racial disparities persisted and in some cases widened. This study identifies lack of improvements in fetal death in the black population compared to the white or Hispanic population at later gestational ages. Keywords First day death
Fetal death
Gestational age
Perinatal mortality
Racial disparities

Introduction For much of the twentieth century, infant and perinatal mortality rates in the United States have been declining [1–4]. However, in recent years the decline has slowed. In 2002, the overall infant mortality rate increased to 7.0 per 1,000 live births, up from 6.8 per 1,000 live births in 2001; the first increase in U.S. infant mortality rate since 1958 [5–7]. Since 2002, U.S. infant mortality rates have been relatively stable [8, 9]. However, state variations in the decline, rise, and stability of infant mortality during selected years have been evident [5, 6, 10]. Additionally racial and ethnic disparities in infant and perinatal mortality continue to increase. By comparison, fetal mortality rates (fetal deaths per 1,000 live births plus fetal deaths) consistently decreased over time; however, the declines were not as substantial as those in infant mortality [2]. Since 1985, the overall U.S. fetal mortality rate has declined 18%, 7.83 per 1,000 live births plus fetal deaths to 6.41 in 2002 [2] compared with a 34% decline from 1985 to 2002 for infant deaths [6]. Additionally, the improvement in overall fetal mortality was due to a decline in late fetal mortality rates (fetal deaths 28 weeks gestation or greater); early fetal mortality rates (fetal deaths\28 weeks gestation) remained unchanged [8]. Disparities between racial and ethnic groups continue to increase as larger declines in infant and fetal mortality occur

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among non-Hispanic whites [8, 11–13] compared with non-Hispanic blacks. The twofold disparities between non-Hispanic blacks and non-Hispanic whites or Hispanics persist as demonstrated by several studies examining the racial and ethnic disparities in perinatal mortality [14–17]. Despite decreases in infant mortality, substantial disparities exist and in some cases continue to grow. For example, the infant mortality of non-Hispanic whites increased slightly from 5.7 infant deaths per 1,000 live births in 2001 to 5.8 infant deaths per 1,000 live births in 2002. For non-Hispanic blacks, infant mortality rates increased from 13.5 in 2001 to 13.9 in 2002 [5]. The infant mortality rate among Hispanics also increased slightly between 2001 and 2002, but the increase over the two time periods was only significant for black infants [5]. One hypothesis for the lack of further declines and stagnant rates of infant mortality (death less than 1 year of age) is a change in perinatal mortality rates as the overall infant mortality rates are influenced by first day deaths and/or fetal deaths. An artificial reduction in fetal deaths may account for a rise in infant deaths; that is, events once classified as fetal death are now classified as first day deaths reflecting misclassification of the timing of death, changes in management of the delivery of very small, very early fetuses, or overall changes in baseline health. The purpose of this study is to examine changes in the gestational-age specific proportions and rates of fetal death, first day death, and combined perinatal death from 1990–1991 to 2001–2002. We considered differences by race and ethnicity, possibly providing some insight into systematic disparities in perinatal health and clinical management. If differences in perinatal or fetal mortality exist between racial and ethnic groups, it is possible that differentials in access to health care or provision of care differ. To our knowledge this is the first study to assess temporal differences in these periods of mortality, particularly first day deaths, by gestational age and race.

Methods We used data from the National Center for Health Statistics 1990–1991 and 2001–2002 linked live birth and infant death cohort files as well as the fetal death files from the same years [18–25]. The files are public access files with all personal identifiers removed and the use of these files for research has been deemed exempt by the Institutional Review Board at the Centers for Disease Control and Prevention and the University of Alabama at Birmingham. We chose to use these years as 1990 and 1991 were the first years and 2001 and 2002 were the last years that all states utilized the vital records certificates with the 1989 revisions. We selected singleton deliveries because of differing survival associated with multiple gestations. Additionally we selected non-Hispanic white (white), Non-Hispanic

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black (black), and Hispanic mothers only. Only deliveries at 20 weeks’ gestation and beyond were included as most states report fetal deaths at 20 weeks or beyond. There is some variability in the birth weight and gestational age requirements for reporting of fetal deaths; however, the three states (New Mexico, South Dakota, and Tennessee) that use birth weight greater than 500 g as the single criterion [2] were excluded from analyses. Fetal mortality (fetal deaths 20 weeks’ gestation or greater) rates were calculated using a denominator of 1,000 live births plus fetal deaths (hereafter referred to as deliveries). First day mortality (infant death less than 24 h after delivery) rates were calculated using a denominator of 1,000 live births; and combined fetal-first day mortality rates were calculated using per 1,000 deliveries. We also calculated the percent change between 1990–1991 and 2001–2002 for each mortality outcome and the overall and race-specific fetal, first day, and combined fetal-first day deaths mortality rates by year category. We calculated chi squares and Cochran-Armitage trend tests for significance. To examine the change in racial and ethnic rates, we calculated the rate ratio both for each race group between birth cohort years, and subsequently for each race group, comparing blacks and whites; blacks and Hispanics; and whites and Hispanics. This calculation allows examination of the racial and ethnic variations and disparities in the change in rates over time. Additionally we calculated gestational age-specific fetal, first day, and combined fetal-first day mortality rates and subsequent combined fetal-first day gestational age-specific mortality rate ratios comparing blacks and whites. Gestational age in completed weeks was computed from the interval between the first day of the last normal menstrual period (LMP) and the date of birth. When there was a valid month and year, records missing date of LMP are imputed on the NCHS file. In cases where no valid month and year of LMP were reported, clinical estimate of gestation was used in the imputation of gestational age. Records with implausible or missing values for birth weight or gestational age and records with a birth weight value inconsistent with the gestational age were excluded. Procedures for imputing data and determining birth weight/gestational age inconsistency have been described in detail elsewhere [26]. For the analysis we used 2-week intervals for gestational age categories (20–21, 22–23, 24–25, 26–27, 28–29, 30–31, 32–33, 34–35, 36–37, 38–39, 40–41, 42?).

Results Between 1990–1991 and 2001–2002 there have been changes in the distribution of US singleton deliveries. As noted in Table 1, there was a 5.18 percent decline

-8.23

First day mortality rate: live births resulting in infant death prior to 24 h after delivery per 1,000 live births

Fetal mortality rate: [20 weeks’ gestation per 1,000 live births plus fetal deaths

Deliveries include both fetal deaths and live births

Combined fetal-first day mortality rate: fetal deaths ? \24 h Deaths per 1,000 live births plus fetal deaths d

c

b

All changes over time are significant at P \ .05

a

-20.66 1.97

7.64 8.32

2.49 -21.43

-14.89 7.50

1.63 2.08

8.81 -4.09

-19.76 4.18

14.59 15.21

5.20 -19.02

1137

-17.24 5.94 6.50 Combined fetal-first day mortality rated

1.53 1.89 First day mortality ratec

-5.18 -2.93 5.66 5.83 46.94 -12.82 20.19 5.87 13.74 6.73 -7.36 4.06 15.98 10.41 17.25 10.01 -7.49 -4.32 63.83 4.41 69.00 4.61 % Deliveriesa Fetal mortality rateb

% Change 01–02 90–91 % Change 01–02 90–91 01–02

% Change

01–02 90–91 90–91

% Change

(1990–1991 = 6,632,645) (2001–2002 = 6,288,861) (1990–1991 = 911,640) (2001–2002 = 1,269,501) (1990–1991 = 1,144,265) (2001–2002 = 1,004,955) (1990–1991 = 4,576,740) (2001–2002 = 4,014,405)

Hispanic Black White Total: 12,921,506

Table 1 Fetal, first day, and combined fetal-first day mortality rates by race and year, 1990–1991 and 2001–2002

Overall

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in overall deliveries between the two time periods. There was a general decrease in overall fetal, first day, and combined fetal-first day mortality rates (Table 1). However, the improvements varied by race and ethnicity. The fetal mortality rate among whites and Hispanics improved 4.32 and 12.82 percent, respectively. However, for blacks, the fetal mortality rate increased 4.06 percent, from 10.01 per 1,000 deliveries in 1990–1991 to 10.41 in 2001–2002. For first day mortality, there was a more than 20 percent decline in mortality rates between the two time periods (2.49 per 1,000 live births in 1990–1991 to 1.97 in 2001–2002). Despite the decline, the black first day mortality rate was still more than triple that of whites or Hispanics in 2001–2002. The combined fetal-first day mortality rate for Hispanics decreased from 8.81 per 1,000 deliveries in 1990–1991 to 7.50 in 2001–2002, a 15 percent decline. Whites had the greatest decline in combined fetal-first day mortality rates (17.2 percent). Despite general improvements in mortality rates, it is important to note continued, and in some cases, increasing disparities. Table 2 provides the rate ratios by race for each mortality outcome category. The ratio of black: white fetal mortality rates increased from 2.17 in 1990–1991 to 2.36 in 2001–2002. Fetal mortality rate ratios increased for black: Hispanic (1.49 to 1.77); the rate ratio for Hispanic: white declined over time (1.46 to 1.27). Despite a continued twofold difference in first day mortality rate between blacks and other racial and ethnic groups, the rate ratios for black: white declined slightly between the two time periods (2.75–2.73) whereas there was a slight increase between black: Hispanic and Hispanic: white. The combined fetalfirst mortality rate ratios for black: white and Hispanic: white increased slightly over the two time periods (Table 2). Table 3 presents gestational age-specific fetal, first day, and combined fetal-first day mortality rates by year and race. For all race groups, there was an increase over time in fetal mortality at 20–21 and 22–23 weeks’ gestation, although the changes over time among Hispanics were not significant. For blacks, there were also increases in fetal mortality from 26–35 weeks’ gestation and at 44? weeks. However, changes were not statistically significant among blacks at 32–33 and 44? weeks. For all gestational ages and races, there were declines in first day mortality rates, although not all temporal changes within racial and ethnic groups were significant. However, for combined fetal-first day mortality, there were declines in mortality at 20–21 weeks for all racial and ethnic groups. Similar to fetal mortality, among blacks, there was an increase in gestational age-specific combined fetal-first day mortality from 28–35 and 44? weeks’ gestational age, but only the increase at 30–31 weeks’ gestation was significant. Racial and ethnic disparities in fetal, \24 h, and combined fetal-first day mortality were evident between blacks

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Table 2 Overall mortality rate ratios by race and year, 1990–1991 and 2001–2002 1990–1991

2001–2002

Black: white

Black: Hispanic

Hispanic: white

Black: white

Black: Hispanic

Hispanic: white

Fetal mortality rate ratioa

2.17

1.49

1.46

2.36

1.77

1.27

First day mortality rate ratioa

2.75

2.51

1.10

2.73

2.56

1.06

Combined fetal-first day mortality rate ratioa

2.34

1.73

1.36

2.46

1.95

1.26

Fetal mortality rate: [20 weeks’ gestation per 1,000 live births plus fetal deaths First day mortality rate: live births resulting in infant death prior to 24 h after delivery per 1,000 live births Combined fetal-first day mortality rate: fetal death ? first day deaths per 1,000 live births plus fetal deaths Changes are significant at P \ .05 a

Calculated by comparing mortality rates 1990–2001 to 2001–2002 for each racial and ethnic group

Table 3 Gestational age-specific fetal, first day, and combined fetal-first day mortality rates by race and year, 1990–1991 and 2001–2002 Fetal mortality ratesa White Black Hispanic 90-1 01-2 90-1 01-2 90-1 01-2 20-1 22-3 24-5 26-7 28-9 30-1 32-3 34-5 36-7 38-9 40-1 42-3 44+

594.02 460.34 290.35 174.01 117.37 70.82 37.72 14.67 5.10 1.58 1.08 1.46 1.70

621.53 491.69 262.67 167.68 110.72 61.36 29.72 12.08 3.94 1.10 0.89 1.24 1.21

473.49 339.30 202.64 127.82 86.62 52.47 28.33 12.47 5.53 2.27 1.66 2.24 1.74

556.77 390.14 187.09 140.74 105.33 60.43 30.88 13.95 5.03 1.79 1.39 2.19 2.05

585.64 479.51 307.74 193.38 148.04 83.05 40.45 14.70 6.65 2.30 1.97 2.79 3.00

665.87 494.21 263.75 183.15 133.80 66.85 33.33 12.60 4.78 1.51 1.24 1.71 1.87

First day mortality ratesb Black White Hispanic 90-1 01-2 01-2 01-2 90-1 90-1 338.01 365.04 205.88 92.59 43.93 22.18 9.71 4.01 1.28 0.34 0.22 0.36 0.36

318.71 307.16 134.44 56.50 30.38 14.83 6.87 2.62 0.74 0.22 0.17 0.22 0.23

363.80 351.18 185.27 70.50 31.49 11.04 4.54 2.17 0.94 0.39 0.41 0.59 0.42

335.55 295.05 114.91 44.44 19.64 10.22 4.68 1.60 0.61 0.29 0.23 0.26 0.11

318.23 327.82 169.04 81.70 34.72 15.32 8.60 2.57 0.92 0.34 0.34 0.52 0.62

253.13 262.78 103.51 53.27 23.92 11.58 6.90 2.38 0.70 0.22 0.22 0.35 0.07

Combined fetal-first day mortality ratesc White Black Hispanic 01-2 90-1 01-2 90-1 01-2 90-1 932.03 825.38 496.23 266.60 161.30 93.00 47.43 18.68 6.37 1.92 1.31 1.82 2.06

940.24 798.85 397.10 224.18 141.10 76.19 36.59 14.70 4.69 1.32 1.06 1.46 1.43

837.29 690.48 387.91 198.32 118.11 63.51 32.87 14.64 6.47 2.66 2.07 2.83 2.16

892.32 685.19 301.99 185.19 124.97 70.64 35.56 15.55 5.64 2.07 1.62 2.45 2.15

903.87 807.33 476.78 275.08 182.76 98.37 49.04 17.27 7.57 2.64 2.31 3.31 3.62

919.00 756.99 367.26 236.41 157.72 78.43 40.23 14.97 5.48 1.73 1.46 2.06 1.95

Shading indicates a significant increase or decrease in gestational-age specific mortality rates between the two time periods within racial/ethnic groups No shading indicates that changes between the two time periods were not significant a

Fetal mortality rate: [20 weeks’ gestation per 1,000 live births plus fetal deaths

b

First day mortality rate: Live births resulting in infant death prior to 24 h after delivery per 1,000 live births

c

Combined fetal-first day mortality rate: Fetal deaths ? first day deaths per 1,000 live births plus fetal deaths

and whites; blacks and Hispanics; and Hispanics and whites. However, the disparities in mortality were greatest between blacks and whites. Figure 1 illustrates the black: white combined fetal-first mortality rate ratios for 1990–1991 and 2001–2002. At earlier gestational ages, the combined fetal-first day mortality rates among blacks were significantly lower compared with whites, as indicated by ratios less than 1. In 1990–1991, statistically significant lower mortality among blacks was evident from 20–21 weeks through 34–35 weeks’ gestation. However in 2001–2002, lower black fetal-first day mortality was demonstrated only from 20–21 to 26–27 weeks’ gestation. This was evidenced as the ratios approached 1 in 2001–2002 compared with 1990–1991. At later gestational ages (38? weeks) in 1990–1991, the black: white ratios were greater than 1, indicating that white fetal mortality rates were significantly

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lower than black fetal mortality rates. This continued in a similar pattern in 2001–2002 and in some cases the ratio increased, indicating that the reductions in fetal deaths among whites and blacks were not uniform.

Comments The purpose of this study was to examine the changes in fetal and first day mortality between 1990–1991 and 2001–2002 with a particular emphasis on racial and ethnic disparities. Unique to this study was the finding that between the early 1990s and early 2000s there was an increase in fetal and combined fetal-first day deaths at early gestational ages for all racial and ethnic groups. The burden, however, was greatest among blacks, with evidence of

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Fig. 1 Gestational age-specific combined fetal-first day mortality rate ratio, blacks compared to whites by year, 1990–1991 and 2001–2002

disparate changes in combined fetal-first day mortality. There was an overall decline in fetal death, first day death, and combined fetal-first day mortality, but improvements were not uniform across all racial and ethnic groups. The fetal death rate among blacks increased significantly between the two time periods while whites and Hispanics experienced substantial improvements. It is important to note that the even though all groups experienced improvements in first day and combined fetal-first day mortality rates, black: white disparities remain more than twofold greater for fetal and first day death. Overall, improvements were more pronounced for first day mortality compared with fetal mortality. As exhibited in previous studies [27–29], deliveries among black mothers at earlier gestational ages had higher survival compared with white infants of similar gestational ages. As gestational age increased the survival advantage for blacks compared with Whites decreased. However in the present study, at younger gestational ages, the advantage of blacks compared with whites decreased from 1990–1991 to 2001–2002, indicating that combined fetal-first day mortality rates were improving more rapidly among whites than blacks. Despite an overall improvement in fetal and first day mortality over time, the racial and ethnic disparity continues to grow. Changes in vital record reporting (i.e., shift in reporting fetal deaths as live births) may have affected black populations disproportionately compared to whites and Hispanics. Although this explanation is plausible, previous studies have cautioned while the data from 2001 and 2002 did suggest an increase in the reporting of early fetal death,

no definitive conclusions could be made regarding a change in reporting [5]. Secondly, the results of this study may be reflective of changes in maternal characteristics over time. Advanced maternal age ([35 years), mothers with high education or more for age, and mothers with medical conditions such as diabetes and hypertension have increased between these two time periods (data not shown). The results may also imply a disparity in early and adequate use of prenatal care, which may result in more advanced interventions, such as the use of steroids, surfactant, and intrapartum antibiotics [30–34], resulting in reductions in perinatal mortality. Some researchers have suggested that in addition to disparities in access to tertiary care hospitals [35], certain therapies, such as surfactant, have differentially benefited white low birth weight infants [36]. In some parts of the United States, blacks are more likely compared with whites to deliver at a tertiary care center [37], suggesting that blacks infants should benefit from interventions aimed at reducing mortality. Interestingly the results of this study showed a disproportionate decline in fetal mortality among whites at term and post-term compared with blacks. This may suggest disparities in maternal care and interventions among term pregnancies that are not being measured using these data. Diabetes, hypoxia, and placental abruption are all possible causes of late fetal death and may be more likely to go undetected in certain subpopulations compared to others. However, further study is needed on racial and ethnic variations in the causes of death as well as access to high-risk obstetrical care. Although our study provides some interesting insights, there are a number of limitations. First, the data are not

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timely due to the limited availability and for some variables, comparability, of the 2003 revision of the live birth and infant and fetal death certificates. Our use of the 1989 version of the certificates was intentional but we recognize that the data are almost a decade old. Previous work has noted issues with secondary data, including missing data, out-of-range data (biologically implausible), and bivariate inconsistency [38, 39]. As noted in recent articles [40–42], the last menstrual period (LMP) gestational age measure compared to the clinical estimate (CE) measure of gestational age results in higher levels of preterm births. Because we used LMP as the measure for gestational age it is possible that the number of very preterm births was overestimated therefore increasing mortality rates at early gestational ages. However based on the previous work of Wingate and Alexander, roughly 50% of records were in exact agreement for LMP and CE with the majority of the discordance between the two gestational age measures occurring between 30 and 35 weeks’ gestation [40], indicating that the earlier gestational ages are potentially not as affected by the LMP versus CE debate. Any misclassification of gestational age calculation by race is considered to be non-differential as later gestational ages could be misclassified equally among all racial groupings. In addition to the consideration of comparisons of LMP and CE is the issue of missing gestational age data. Of particular concern is that infants born to women of low socioeconomic status and those receiving late prenatal care have higher rates of missing gestational age information [43, 44], suggesting that the reporting of gestational age for blacks and Hispanics is lower due to missing data. This could underestimate our results if infants and/or fetuses with missing gestational age are more common among combined fetal-first day deaths to blacks and/or Hispanics. In this study, the percent of missing gestational age (LMP or CE) information decreased between the two time periods for whites (0.76 percent in 1990–1991 to 0.54 in 2001–2002). The percent for Hispanics increased slightly from 2.32 percent to 2.70 percent. However, whites continued to have the lowest percent of missing gestational age information compared to blacks or Hispanics. Also reporting of gestational age varies by state. For example, during the time period of this study, California did not gather data on clinical estimate of gestational age. Because there is a high proportion of Hispanics in California, our data for Hispanics may have been skewed due to limited reporting [18–25]. Previous studies that have examined the gestational age reporting issues (comparison of LMP to clinical estimate) encourage cautious interpretation of infant and fetal mortality information presented in this and other studies [40–42]. Additionally, states differ in their reporting requirements of birth weight and gestational ages for both fetal deaths and live births. Some states require reporting of all

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products of conception whereas others require a delivery to be at least 20 weeks’ gestation or 500 g and other variations [2]. It is important to note that the rates presented for each racial and ethnic group may be slightly altered due to the variability in racial and ethnic composition by state. Finally despite the standard adoption of the WHO definitions of live birth and fetal death, there may be differences in clinical practice definitions of death at early gestational ages and very small birth weights [45, 46]. This study does provide evidence that despite widespread improvement overall, the disparities in fetal, first day, and combined fetal-first day mortality have changed over time. In some cases there has been improvement, but generally, at very early gestational ages the improvements have not been evident. Presumably deliveries at very early gestational ages and very low birth weights can only be improved as the age of viability improves. In order to reduce infant mortality, the number of preterm births must be reduced, particularly those at early gestational ages. However, this study does highlight opportunities for improvement in mortality in some racial and ethnic groups at later gestational ages. Racial disparities continue to grow among mid to late fetal deaths, suggesting that clinical management or health service availability may not be uniform across all racial and ethnic groups. Future studies are needed to provide further insight into this question. Additionally, studies should consider maternal risk characteristics (diabetes, hypertension, obesity, etc.) as related to these changes in gestational-age specific fetal and first day mortality. This study has confirmed that combined fetal-first day mortality rates are declining but that these declines differ by race and ethnicity and gestational age. Importantly, we have identified lack of improvements in the black population at later gestational ages, where we have the medical technology to identify and potentially prevent lateterm fetal deaths. Fetal death has been called ‘‘a major, but often overlooked public health problem [3].’’ Public health efforts should continue to focus on identification of fetal death data quality, surveillance, causes, and prevention. Acknowledgments Dr. Wingate was supported in part by CDC IPA 899290 and in part by DHHS, HRSA, MCHB grant MC00008. The content of this work is solely the responsibility of the authors and does not necessarily represent the official views of the Centers for Disease Control and Prevention or other funding agencies. Disclaimer The findings and conclusions of this report are those of the authors and do not necessarily represent the official position of the Centers for Disease Control and Prevention.

References 1. Guyer, B., Freedman, M. A., Strobino, D. M., & Sondik, E. J. (2000). Annual summary of vital statistics: Trends in the health of Americans during the 20th century. Pediatrics, 106, 1307–1317.

Matern Child Health J (2011) 15:1135–1142 2. MacDorman, M. F., & Kirmeyer, S. (2009). Fetal and perinatal mortality, United States, 2005. National vital statistics report; Vol. 57, no. 8. Hyattsville, Maryland: National Center for Health Statistics. 3. MacDorman, M., & Kirmeyer, S. (2009). The challenge of fetal mortality. NCHS data brief, no. 16. Hyattsville, MD: National Center for Health Statistics. 4. MacDorman, M. F., & Mathews, T. J. (2008). Recent trends in infant mortality in the United States. NCHS brief, no. 9. Hyattsville, MD: National Center for Health Statistics. 5. MacDorman, M. F., Martin, J. A., Mathews, T. J., Hoyert, D. L., & Ventura, S. J. (2005). Explaining the 2001–02 infant mortality increase: Data from the linked birth/infant death data set. National vital statistics report; Vol. 53, no. 12. Hyattsville, Maryland: National Center for Health Statistics. 6. Kochanek, K. D., & Martin, J. A. (2005). Supplemental analyses of recent trends in infant mortality. International Journal of Health Services, 35(1), 101–115. 7. Kochanek, K. D., Murphy, S. L., Anderson, R. N., & Scott, C. (2004). Deaths: Final data for 2002. National vital statistics report; Vol. 53, no. 5. Hyattsville, Maryland: National Center for Health Statistics. 8. Martin, J. A., Kung, H., Matthews, T. J., Hoyert, D. L., Strobino, D. M., Guyer, B., et al. (2006). Annual summary of vital statistics: 2006. Pediatrics, 121(4), 788–801. 9. Kung, H. C., Hoyert, D. L., Xu, J. D., & Murphy, S. L. (2005). Deaths: Final data for 2005. National vital statistics report; Vol. 56, no. 10. Hyattsville, Maryland: National Center for Health Statistics. 10. Centers for Disease Control and Prevention. (2003). Increasing infant mortality among very low birthweight infants—Delaware, 1994–2000. MMWR, 52(36), 862–866. 11. Centers for Disease Control and Prevention. (2002). Infant mortality and low birth weight among black and white infants— United States, 1980–2000. MMWR, 51, 589–592. 12. Alexander, G. R., & Slay, M. (2002). Prematurity at birth: Trends, racial disparities, and epidemiology. Mental Retardation and Developmental Disabilities Research Reviews, 8, 215–220. 13. Carmicheal, S. L., & Iyasy, S. (1998). Changes in the black– white infant mortality gap from 1983–1991 in the United States. American Journal of Preventive Medicine, 15, 220–227. 14. Ananth, C. V., Kinzler, W., & Kramer, M. S. (2005). Stillbirths in the United States, 1981–2000: An age, period, and cohort analysis. American Journal of Public Health, 95(12), 2213–2217. 15. Reddy, U. M., Ko, C. W., & Willinger, M. (2006). Maternal age and the risk of stillbirth throughout pregnancy in the United States. American Journal of Obstetrics and Gynecology, 195(3), 764–770. 16. Barfield, W. D., Tomashek, K. M., Flowers, L. M., & Iyasu, S. (2002). Contribution of late fetal deaths to US perinatal mortality rates, 1995–1998. Seminars in Perinatology, 26(1), 17–24. 17. Wingate, M. S., & Alexander, G. R. (2006). Racial and ethnic differences in perinatal mortality: The role of fetal death. Annals of Epidemiology, 16(6), 485–491. 18. National Center for Health Statistics. (1990). Fetal death data and user’s guide. Hyattsville, MD: National Center for Health Statistics. Available from http://www.cdc.gov/nchs/about/major/dvs/ vitalstatsonline.htm. 19. National Center for Health Statistics. (1990). Birth cohort linked birth/infant death data and user’s guide. Hyattsville, MD: National Center for Health Statistics. Available from http:// www.cdc.gov/nchs/about/major/dvs/vitalstatsonline.htm. 20. National Center for Health Statistics. (1991). Fetal death data and user’s guide. Hyattsville, MD: National Center for Health Statistics. Available from http://www.cdc.gov/nchs/about/major/dvs/ vitalstatsonline.htm. 21. National Center for Health Statistics. (1991). Birth cohort linked birth/infant death data and user’s guide. Hyattsville, MD:

1141

22.

23.

24.

25.

26.

27.

28.

29.

30.

31.

32. 33.

34.

35.

36.

37.

38.

39.

National Center for Health Statistics. Available from http://www. cdc.gov/nchs/about/major/dvs/vitalstatsonline.htm. National Center for Health Statistics. (2001). Fetal death data and user’s guide. Hyattsville, MD: National Center for Health Statistics. Available from http://www.cdc.gov/nchs/about/major/ dvs/vitalstatsonline.htm. National Center for Health Statistics. (2001). Birth cohort linked birth/infant death data and user’s guide. Hyattsville, MD: National Center for Health Statistics. Available from http:// www.cdc.gov/nchs/about/major/dvs/vitalstatsonline.htm. National Center for Health Statistics. (2002). Fetal death data and user’s guide. Hyattsville, MD: National Center for Health Statistics. Available from http://www.cdc.gov/nchs/about/major/dvs/ vitalstatsonline.htm. National Center for Health Statistics. (2002). Birth cohort linked birth/infant death data and user’s guide. Hyattsville, MD: National Center for Health Statistics. Available from http://www. cdc.gov/nchs/about/major/dvs/vitalstatsonline.htm. Alexander, G. R., Himes, J. H., Kaufman, R. B., Mor, J., & Kogan, M. (1996). A United States national reference for fetal growth. Obstetrics and Gynecology, 87(2), 163–168. Alexander, G. R., Tompkins, M. E., Allen, M. C., et al. (1999). Trends and racial differences in birth weight and related survival. Maternal and Child Health Journal, 3(1), 71–79. Allen, M. C., Alexander, G. R., Tompkins, M. E., et al. (2000). Racial differences in temporal changes in newborn viability and survival by gestational age. Paediatric and Perinatal Epidemiology, 14, 152–158. Allen, M. C., Donohue, P. K., & Dusman, A. E. (1993). The limit of viability—Neonatal outcome of infants born at 22 to 25 weeks’ gestation. New England Journal of Medicine, 329(22), 1597–1601. Eichenwald, E. C., & Stark, A. R. (2008). Management and outcomes of very low birth weight. New England Journal of Medicine, 358(16), 1700–1711. Morse, S. B., Haywood, J. L., Goldenberg, R. L., Bronstein, J., Nelson, K. G., & Carlo, W. A. (2000). Estimation of neonatal outcome and perinatal therapy use. Pediatrics, 105(5), 1046–1050. Eichenwald, E. C., & Stark, A. R. (1999). High-frequency ventilations: Current status. Pediatrics in Review, 20(12), e127–e133. Schwartz, R. M., Luby, A. M., Scanlon, J. W., et al. (1994). Effects of surfactant on morbidity, mortality, and resource use in newborn infants weighing 500 to 1500 g. New England Journal of Medicine, 330(21), 1476–1480. Howell, E. M., & Vert, P. (1993). Neonatal intensive care and birth weight-specific perinatal mortality in Michigan and Lorraine. Pediatrics, 91(2), 464–470. Langkamp, D. L., Foye, H. R., & Roghmann, K. J. (1990). Does limited access to NICU services account for higher neonatal mortality rates among blacks? American Journal of Perinatology, 7(3), 227–231. Hamvas, A., Wise, P. H., Yang, R. K., Wampler, N. S., Noguchi, A., Maurer, M. M., et al. (1996). The influence of the wider use of surfactant therapy on neonatal mortality among blacks and whites. New England Journal of Medicine, 334, 1635–1640. Alexander, G. R., Petersen, D. J., & Allen, M. C. (2000). Life on the edge: Preterm births at the limit of viability—Committed to their survival, are we equally committed to their prevention and long-term care? Medicolegal OB/Gyn Newsletter, 8, 18–21. Petersen, D. J., & Alexander, G. R. (1997). Threats to accurate interpretation of secondary data. Maternal and child health: Programs, problems, and policy in public health. In J. B. Kotch (Ed.), Maternal and child health: Principles and practice in public health (2nd ed., pp. 395–404). Gaithersburg, MD: Aspen Press. Alexander, G. R., Petersen, D. J., Wingate, M. S., & Kirby, R. S. (2005). Research issues in MCH. In J. B. Kotch (Ed.), Maternal

123

1142 and child health: Principles and practice in public health (2nd ed.). Gaithersburg, MD: Aspen Press. 40. Wingate, M. S., Alexander, G. R., Buekens, P., & Vahratian, A. (2007). Comparison of gestational age classifications: Date of last menstrual period vs. clinical estimate. Annals of Epidemiology, 17(6), 425–430. 41. Martin, J. A. (2007). United States vital statistics and the measurement of gestational age. Paediatric and Perinatal Epidemiology, 21(Suppl. 2), 13–21. 42. Ananth, C. V. (2007). Menstrual versus clinical estimate of gestational age dating in the United States: Temporal trends and variability in indices of perinatal outcomes. Paediatric and Perinatal Epidemiology, 21(Suppl. 2), 22–30.

123

Matern Child Health J (2011) 15:1135–1142 43. Buekens, P., Delvoye, P., Wollast, E., & Robyn, C. (1984). Epidemiology of pregnancies with unknown last menstrual period. Journal of Epidemiology and Community Health, 38, 79–80. 44. David, R. J. (1980). The quality and completeness of birth weight and gestational age data in computerized birth files. American Journal of Public Health, 70, 964–973. 45. MacDonald, H., & The Committee on Fetus and Newborn. (2002). Perinatal care at the threshold of viability. Pediatrics, 110(5), 1024–1027. 46. Tyson, J. E., Parikh, N. A., Langer, J., Green, C., & Higgins, R. D. (2008). Intensive care for extreme prematurity—Moving beyond gestational age. New England Journal of Medicine, 358, 1672–1681.