Birth weight trends among interracial black and white infants

I examined time trends in low birth weight (LBW) and very low birth weight (VLBW) among interracial compared with single-race infants. Using natality data from 1978 through 1997 for singleton births to black and white parents, I calculated relative risks (RRs) of LBW and VLBW for interracial compared with single-race births, stratified by maternal race and adjusted for maternal characteristics. Among black mothers, interracial births had lower risks of LBW and VLBW than single-race births, and RRs were similar throughout the time period [for example, adjusted RR = 0.76 and 95% confidence interval (CI) = 0.73-0.80 for LBW in 1994-1997]. Among white mothers, interracial infants had higher risks of LBW than single-race infants; however, the adjusted RRs declined over the time period, from 1.22 (95% CI = 1.19-1.27) in 1978-1981 to 1.05 (95% CI = 1.03-1.08) in 1994-1997. Since 1978, there has been some relative improvement in birth outcomes for infants of white mothers and black fathers compared with single-race white births. There was, however, no relative improvement for black mother/black father infants relative to black mother/white father births.     

Multiple-race mortality data for California, 2000-2001

OBJECTIVES: To examine mortality rates and quality of race reporting for multiple-race individuals in California using the new multiple-race data available on the death certificate. METHODS: Death date were drawn from California vital statistics for 2000 and 2001. Denominator data were drawn from the 2000 census Modified Race Data Summary File. The authors calculated mortality rates and relative standard errors for multiple-race individuals as a whole and by county, and for the three largest reported multiple-race groups (African American and white, American Indian/Alaska Native and white, and Asian and white). RESULTS: Decedents reported to be of more than one race were disproportionately young, Hispanic, male, and never-married. Age-adjusted mortality rates for multiple-race groups were approximately one-sixth as high as rates for single-race individuals. There was substantial variability in rates for multiple-race decedents according to county of residence. CONCLUSIONS: Mortality rates for multiple-race people were implausibly low, and death certificates for multiple-race individuals were geographically clustered. Race reporting on death certificates will need to be improved before accurate death rates can be calculated for those of multiple races.     

The correspondence between interracial births and multiple-race reporting

OBJECTIVES: Race-specific health statistics are routinely reported in scientific publications; most describe health disparities across groups. Census 2000 showed that 2.4% of the US population identifies with more than 1 race group. We examined the hypothesis that multiple-race reporting is associated with interracial births by comparing parental race reported on birth certificates with reported race in a national health survey. METHODS: US natality data from 1968 through 1998 and National Health Interview Survey data from 1990 through 1998 were compared, by year of birth. RESULTS: Overall multiple-race survey responses correspond to expectations from interracial births. However, there are discrepancies for specific multiple-race combinations. CONCLUSIONS: Projected estimates of the multiple-race population can be only partially informed by vital records.     

Mind the gap: bridge methods to allocate multiple-race mothers in trend analyses of birth certificate data

Objectives: To examine the effects of proposed methods of redistributing multiple-race mothers to single-race categories when computing trend data from birth certificates. Methods: Low birthweight and multiple (twin and higher-order) birthrates for California were calculated for non-Hispanic mothers from birth certificate data for 2000. Births to the 1.9% of mothers identified as multiple-race were reassigned to single-race groups according to 12 bridging methods. Bridge methods utilized population-based whole allocation, fractional allocation, and other methods, primarily depending on first race listed. Results: For large race groups, there was little difference in low birthweight and multiple birth rates regardless of the bridge method employed. For smaller groups such as Native Hawaiians and other Pacific Islanders and American Indians/Alaska Natives, there was substantial variation by bridge method in observed rates. Conclusions: Tracking trends in birth outcomes across the change indata collection will challenge public health researchers. This paper outlines advantages and disadvantages of various bridge methods.     

Maternal Obesity and Risk of Preterm Birth and Low Birthweight in Hawaii PRAMS, 2000–2011

Objective Maternal obesity is a risk factor for preterm birth, a leading cause of infant morbidity and mortality. Native Hawaiian and other Pacific Islanders (NHOPI) have high rates of poor birth outcomes. Despite the high rates of obesity in NHOPI in Hawaii, the association with preterm birth has not been examined in this population. Methods We performed a retrospective cohort study of 20,061 women using data collected by Hawaii’s Pregnancy Risk Assessment Monitoring System (PRAMS) from 2000 to 2011. We investigated the contribution of maternal age, pre-pregnancy BMI, gestational diabetes, hypertension, race, socioeconomic status, and smoking to our primary outcomes of preterm birth and low birthweight using multivariable logistic regression, stratified by NHOPI versus non-NHOPI race. Results Pre-pregnancy obesity was more common in NHOPI than non-NHOPI women (23.9 and 10.5%, respectively; p?<?0.01). Overall, the risk for preterm birth increased with maternal obesity (BMI?≥?30.0; aOR?=?1.24, 95% CI 1.06–1.45, p?<?0.01), compared with normal weight women. Among NHOPI women, the prevalence of preterm birth was elevated compared with non-NHOPI women although the prevalence of low birth weight was lower. After adjusting for confounders, risk for preterm birth and low birth weight were elevated in NHOPI women compared with White women. Maternal obesity did not significantly affect the risk of prematurity within the NHOPI group. Conclusions for Practice Our study demonstrates an association between maternal pre-pregnancy obesity and preterm deliveries in Hawaii. NHOPI have high rates of pre-pregnancy obesity as well as increased risk of both preterm delivery and low birthweight when compared to White women. Further data are needed to assess interactions between race, maternal health, and neonatal morbidity, and to identify ways to improve birth outcomes for minority populations in the state of Hawaii.     

Bridging between two standards for collecting information on race and ethnicity: an application to Census 2000 and vital rates

OBJECTIVES: The 2000 Census, which provides denominators used in calculating vital statistics and other rates, allowed multiple-race responses. Many other data systems that provide numerators used in calculating rates collect only single-race data. Bridging is needed to make the numerators and denominators comparable. This report describes and evaluates the method used by the National Center for Health Statistics to bridge multiple-race responses obtained from Census 2000 to single-race categories, creating single-race population estimates that are available to the public. METHODS: The authors fitted logistic regression models to multiple-race data from the National Health Interview Survey (NHIS) for 1997-2000. These fitted models, and two bridging methods previously suggested by the Office of Management and Budget, were applied to the public-use Census Modified Race Data Summary file to create single-race population estimates for the U.S. The authors also compared death rates for single-race groups calculated using these three approaches. RESULTS: Parameter estimates differed between the NHIS models for the multiple-race groups. For example, as the percentage of multiple-race respondents in a county increased, the likelihood of stating black as a primary race increased among black/white respondents but decreased among American Indian or Alaska Native/black respondents. The inclusion of county-level contextual variables in the regression models as well as the underlying demographic differences across states led to variation in allocation percentages; for example, the allocation of black/white respondents to single-race white ranged from nearly zero to more than 50% across states. Death rates calculated using bridging via the NHIS models were similar to those calculated using other methods, except for the American Indian/Alaska Native group, which included a large proportion of multiple-race reporters. CONCLUSION: Many data systems do not currently allow multiple-race reporting. When such data systems are used with Census counts to produce race-specific rates, bridging methods that incorporate geographic and demographic factors may lead to better rates than methods that do not consider such factors.     

Asthma prevalence disparities and differences in sociodemographic associations with asthma,between Native Hawaiian/Other Pacific Islander,Asian, and White adults in Hawaii – Behavioral Risk Factor Surveillance System (BRFSS), 2001–2010

Objectives: Despite high asthma prevalence, relatively little is known about the epidemiology of asthma in Hawaii or among Native Hawaiian/Other Pacific Islanders (NHOPI). We sought to better characterize racial/ethnic differences in asthma prevalence and in sociodemographic factors associated with asthma among Hawaii adults.

Design: We conducted multivariable logistic regression using 2001–2010 Behavioral Risk Factor Surveillance System data from Hawaii, and computed adjusted prevalence and ratios.

Results: Asthma prevalence markedly varied between self-identified census categories of race in Hawaii, with NHOPI having the highest estimates of both lifetime (20.9%, 95% confidence interval [CI]: 19.5%–22.4%) and current (12.2%, CI: 11.2%–13.3%) asthma. Highest asthma prevalence among NHOPI persisted after controlling for potential confounders and within most sociodemographic categories. Among females Asians reported the lowest asthma prevalence, whereas among males point estimates of asthma prevalence were often lowest for Whites. Females often had greater asthma prevalence than males of the same race, but the degree to which gender modified asthma prevalence differed by both race and sociodemographic strata. Gender disparities in asthma prevalence were greatest and most frequent among Whites, and for current asthma among all races. Sociodemographic factors potentially predictive of adult asthma prevalence in Hawaii varied by race and gender.

Conclusion: Asthma disproportionately affects or is recognized more often among women and NHOPI adults in Hawaii, and occurs less or is under-reported among Asian women. The sociodemographic characteristics included in this study’s model did not explain asthma disparities between races and/or gender. This investigation provides a baseline with which to plan additionally needed prevention programs, epidemiological investigations, and surveillance for asthma in Hawaii.     

Preterm singleton births--United States, 1989-1996

Preterm birth (birth at <37 completed weeks of gestation) is the second leading cause of neonatal mortality in the United States. Preterm birthrates differ by race; in 1996, black infants were 1.8 times more likely than white infants to be preterm. From 1989 through 1996, the overall rate of preterm birth (per 1000 live-born infants) increased 4%, and the rate of multiple births (e.g., twins, triplets, or other higher-order births) increased 19%. Multiple births are associated with preterm birth; trends in preterm births independent of the influence of multiple births have not been fully explored. To characterize race- and ethnicity-specific trends in preterm birth independent of multiple births, data from U.S. birth certificates for 1989-1996 were analyzed for singleton births only. This report summarizes the results of this analysis and indicates that although singleton preterm birthrates are stable overall, substantial changes in rates occurred in some racial/ethnic subgroups.     

Characteristics of mothers of live infants with congenital syphilis in Florida, 1987-1989.

The incidence of congenital syphilis in Florida increased sixfold from 1985 through 1989, and more than 80% of the cases occurred in metropolitan areas of southern Florida. To characterize the population of pregnant women in Florida at high risk of delivering an infant with congenital syphilis, the authors conducted a case-control study using birth certificates. Birth certificates were obtained for 256 of the 344 live infants reported as having congenital syphilis from 1987 through 1989 (74%); the 246 of these infants born in hospitals were matched for hospital and week of birth with an equal number of controls. In conditional multiple logistic regression, the following maternal characteristics were independent risk factors for congenital syphilis: young age, black race, single marital status, absence of a father's name on the birth certificate, previous pregnancy, substance abuse, and lack of prenatal care. Although the national origin of the mother was not a significant risk factor, the infants of black mothers born in the United States were at greater risk than the infants of black mothers born outside the United States. Mothers who had < or = 3 prenatal visits had an increased risk of delivering an infant with congenital syphilis as compared with mothers who had > 3 visits. This study suggests that targeted outreach efforts are necessary to control congenital syphilis and provides guidance for public health intervention activities.     

Heterogeneity within Asian Subgroups: A Comparison of Birthweight Between Infants of US and Non-US Born Asian Indian and Chinese Mothers

Objectives Birthweight distributions and proportions of low birthweight (LBW) are commonly used to assess the health of populations. However, the “population” is difficult to define due to differences by race, socioeconomic status, age distribution, and cultural identity. This study analyzes birth outcomes in two Asian subgroups to examine variation within the Asian population. Methods Analysis of the 1998–2003 National Center for Health Statistics’ natality file for 293,211 singleton births in Asian Indian and Chinese mothers compared birthweight distributions, mean birthweights, proportions of very low birthweight (VLBW) and moderately low birthweight (MLBW) infants, and the influence of maternal nativity on these outcomes. A multiple logistic regression analysis, stratified by maternal nativity, was done to control for established confounders of maternal age, marital status, education, and parity. Results Maternal characteristics and birthweight distributions varied by race subgroup and nativity. Infants of Asian Indian mothers had a lower mean birthweight and higher proportions of VLBW and MLBW than Chinese. After controlling for differences in maternal characteristics, infants of US born Asian Indian mothers were more likely to be VLBW (AOR 1.87, 95% CI: 1.27–2.75) or MLBW (AOR 1.59, 1.39–1.82) than infants of US born Chinese mothers. Similarly, infants of non-US born Asian Indian mothers were more likely to be VLBW (AOR 2.13, 2.06–2.21) or MLBW (AOR 2.26, 2.18–2.35) then infants of non-US born Chinese mothers. Conclusions Our study demonstrates variation in birth outcomes by maternal race and nativity in two Asian subgroups. The heterogeneity within a single commonly used “population” is likely not limited to these two Asian subgroups, but is probably applicable to many populations in the United States. Analyses should try to account for these differences to ensure a more accurate representation of various populations in the US. The difficulty of defining a population by race adds to the complexity of examining disparities in birth outcomes.     

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.     

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.     

Maternal, pregnancy, and birth characteristics of Asians and Native Hawaiians/Pacific Islanders--King County, Washington, 2003-2008

In 1997, the Office of Management and Budget issued revised standards for reporting race and ethnicity in federal datasets. In addition to permitting the reporting of two or more races for each record, the revised standards separated the "Asian or Pacific Islander" category into two categories: "Asian" and "Native Hawaiian or other Pacific Islander" (NHPI). To quantify the health status of NHPI mothers and infants in King County, Washington, 2003-2008 vital statistics for NHPI disaggregated from Asians were used to assess several key maternal and birth outcome indicators. This analysis determined that, compared with Asians in King County, NHPI mothers were significantly more likely to be adolescents, overweight or obese before pregnancy, or to have smoked during pregnancy, and their infants were more likely to be born preterm, weigh>4,500 g, or receive either third trimester only or no prenatal care. These results identify important differences and support routine presentation of health data separately for Asians and NHPIs.     

Disparities in Use of Mental Health and Substance Abuse Services by Asian and Native Hawaiian/Other Pacific Islander Women

The purpose of this study was to determine if disparities exist in lifetime utilization of mental health/substance abuse services among Asian, Native Hawaiian/Other Pacific Islander (NHOPI) and white mothers. The study sample was comprised of mothers assessed to be at-risk (n = 491) and not at-risk (n = 218) for child maltreatment in the Hawaii Healthy Start Program study. Multiple logistic regression models were used to test the effects of predisposing, need, and enabling factors on utilization of services. Results revealed that, among mothers with depressive symptoms, compared with whites, Asians and NHOPI were significantly less likely to have received services. There were no significant racial differences in use of mental health/substance use services by other factors. These results suggest that racial disparities exist in utilization of mental health/substance abuse services among mothers with depressive symptoms. Future research is needed to identify barriers and facilitators to accessing needed services for Asian and NHOPI women.     

Infant mortality among racial/ethnic minority groups, 1983-1984

Infant mortality varies considerably among racial/ethnic groups in the United States. For groups other than whites and blacks, previously published rates based on the vital statistics system have been underestimated because of inconsistencies in the classification of race and Hispanic status on birth and death certificates. For this report, infant mortality rates (IMRs) are based on the 1983 and 1984 linked birth and infant-death files, and mother's race and Hispanic origin are reported in accordance with information shown on the birth certificates. Overall, Asians have somewhat lower infant mortality rates than whites, but the rates vary from 6.0/1,000 among Japanese mothers to 9.0/1,000 among "other Asian" mothers. Hispanic mothers show even wider variation: from 7.8/1,000 among Cubans to 12.9/1,000 among Puerto Ricans. Blacks have an IMR twice as high as that for whites, and the rate for American Indians is nearly 60% above the rate for whites. Mexicans are the third largest minority group in the United States, accounting for one-quarter million births per year. Despite a high rate of poverty and low use of prenatal care, Mexicans have approximately the same IMR (9.0/1,000) as non-Hispanic whites. Further study of this group could assist in the development of prevention strategies.     

From single-race reporting to multiple-race reporting: using imputation methods to bridge the transition

In 1997, the Office of Management and Budget issued revised standards for the collection of race information within the Federal statistical system. One revision allows individuals to choose more than one race group when responding to Federal surveys and other Federal data collections. This paper explores methods that impute single-race categories for those who have given multiple-race responses. Such imputations would be useful when it is desired to conduct analyses involving only single-race categories, such as when trends over time are being examined by race group so that data collected under the old and new standards are being combined. The National Health Interview Survey has allowed multiple-race responses for several years, while also asking respondents to specify one race as their primary race. Exploratory analyses of data from the survey suggest that imputation methods that use demographic and contextual covariate information to predict primary race can have advantages with respect to lower bias and improved variance estimation compared to simpler methods discussed by the Office of Management and Budget. It also appears, however, that the relationships between primary race and covariates might be changing over time. Thus, caution should be exercised if an imputation model fitted to data from one time period is to be applied to data from another time period. Published in 2003 by John Wiley & Sons, Ltd.     

Changing pregnancy outcomes of Samoan women in Hawaii

In the state of Hawaii, Samoan mothers are known for the large average birthweight and low percentage of low birthweight (< 2500 g) of their infants, in spite of the relatively low socio-economic status of the population. This paper reports the findings of a temporal trend analysis of birth outcomes of Samoan women and identifies worrying changes. Data were obtained from Hawaii birth certificates. Single live births to Hawaii-resident Samoan and Caucasian women from 1979 to 1994 were included in the study. Infants of Samoan women experienced a 75 g decline in mean birthweight and an increase in the percentage of low (< 2500 g) and very low (< 1500 g) birthweight from 2.6 and 0.4 to 3.8 and 0.8 respectively. During the same time, infants of Caucasian mothers experienced an increase in mean birthweight and a decline in low birthweight, while very low birthweight did not change. Maternal socio-demographic characteristics explained only part of the findings and use of prenatal care did not appear to be associated with any birth outcome indicators. Multiple regression analyses identified an adjusted loss of 50.8 g in birthweight and a 1.48 increase in the odds ratio of small-for-gestational-age associated with birth at the end (1991-4) compared with the beginning (1979-82) of the study period. Further studies focusing on maternal health status and psycho-social variables, including the effect of acculturation-related stress, are warranted to identify at least some of the determinants of the changes identified by this analysis.