State-specific changes in singleton preterm births among black and white women--United States, 1990 and 1997

National infant mortality rates among non-Hispanic black women are twice those of non-Hispanic white women (1). Nearly two-thirds of this disparity is attributable to a higher rate of preterm delivery (PTD) (i.e., < or = 37 weeks' gestation) among blacks (2). To investigate state-specific changes in PTD rates among blacks and whites, natality data for 1990 and 1997 were analyzed from 50 states and the District of Columbia (DC). These data indicated that, although the PTD rate was twice as high among blacks than among whites, the disparity decreased as the result of an increase in preterm births among whites and a decrease among blacks (3).     

Racial differences in the patterns of preterm delivery in central North Carolina, USA

Summary. In order to assess racial differences in rates of idiopathic preterm labour, preterm premature rupture of membranes, and medically indicated preterm delivery, the authors analysed data on 388 preterm (< 37 completed weeks of gestation) births (7.9% of all births) occurring between 1 September 1988 and 31 August 1989, in three central North Carolina counties. The crude relative risk (RR) of preterm birth among black women compared with white women was 2.6 [95% confidence interval (CI) 2.1, 3.1]. With adjustment for age, gravidity, marital status, education, and county of residence, the estimated relative risk for black women compared with white women was 2.1 (95% CI 1.1,4.1) for medically indicated preterm delivery, 1.6 (95% CI 1.1,2.3) for preterm birth as a result of preterm labour, and 1.9 (95% CI 1.2,3.1) for preterm premature rupture of membranes. Compared with white women, black women were at the highest risk of a preterm birth before 34 weeks of gestation (RR = 2.9; 95% CI 1.8, 4.7). The risk of medically indicated preterm delivery at 36 weeks was considerably higher for black women than for white women (RR = 3.4; 95% CI 1.1,10.2). For a better understanding and ultimately a reduction of the risk for preterm delivery among black women, investigation of specific aetiological pathways and gestational age groups may be required.     

Employment-related stress and preterm delivery: a contextual examination.

Studies of employment-related stress as a risk factor for preterm delivery suggest that contextual factors unrelated to occupation, as well as work-related characteristics, must be examined in assessing this relationship. In this study, the relationship of work and contextual characteristics--assessed at midpregnancy and including scores on an occupational fatigue index--to preterm delivery was examined among 943 black and 425 white low-income multiparous women who were at risk for a poor pregnancy outcome. At 24 to 26 weeks gestational age, a 77-item questionnaire was self-administered to obtain detailed information on sociodemographic and contextual characteristics, home physical activities, and occupational characteristics. Questions in the occupational section of the questionnaire included most of those previously used by Mamelle and coworkers in 1984 and 1987 to construct an occupational fatigue index. The overall preterm delivery rate for black women was 14.0 percent and for white women, 9.6 percent. No relationships were observed between age, education, or marital status and preterm delivery, or between work status, hours per week, transportation, travel time, reliability of child care, or home physical activity and preterm delivery for either black women or white women. Black (but not white) women who continued to work at midpregnancy and who reported being able to take rest breaks when they felt tired had a lower preterm delivery rate (10.4 percent versus 21.9 percent; P = 0.031) compared with those who could or did not.(ABSTRACT TRUNCATED AT 250 WORDS)     

Commentary: Eliminating Disparities in Perinatal Outcomes—Lessons Learned

The disparity between blacks and whites in perinatal health ranges from a 2.3-fold excess risk among black women for preterm delivery and infant mortality to a 4-fold excess risk among black women for maternal mortality. To stimulate concerted public health action to address such racial and ethnic disparities in health, the national Healthy People objectives call for elimination of all health disparities by the year 2010. Eliminating health disparities requires a greater understanding of the factors that contribute to their development. This commentary summarizes the state of the science of reducing such disparities and proposes a framework for using the results of qualitative studies on the social context of pregnancy to understand, study, and address disparities in infant mortality and preterm delivery. Understanding the social context of African American women's lives can lead to an improved understanding of the etiology of preterm birth, and can help identify promising new interventions to reduce racial and ethnic disparities in preterm delivery.     

Why do Black Americans have a higher risk of pancreatic cancer than White Americans?

BACKGROUND: For several decades, the incidence of pancreatic cancer has been 50% to 90% higher among blacks than among whites in the United States. The purpose of this study was to identify risk factors that may contribute to this racial disparity. METHODS: We conducted a population-based case-control study of pancreatic cancer diagnosed in Atlanta (GA), Detroit (MI), and 10 New Jersey counties from August 1986 through April 1989. In-person interviews were exclusively with subjects (526 cases and 2153 population controls), rather than with next of kin. RESULTS: The determinants of the higher incidence of pancreatic cancer among blacks than among whites differed by sex. Among men, established risk factors (, cigarette smoking, long-term diabetes mellitus, family history of pancreatic cancer) account for 46% of the disease in blacks and 37% in whites, potentially explaining all but 6% of the excess risk among blacks. Among women, however, other factors appear to contribute to the racial disparity, notably moderate/heavy alcohol consumption (>7 drinks per week) and elevated body mass index (above the first quartile). When these less accepted risk factors were combined with the established risk factors, 88% of the disease in black women and 47% in white women were explained, potentially accounting for all of the excess risk among blacks in our female study population. CONCLUSIONS: Among men, the established risk factors (mainly cigarette smoking and diabetes mellitus) explain almost the entire black/white disparity in incidence. Among women, however, other factors appear to contribute to the racial disparity, notably moderate/heavy alcohol consumption and elevated body mass index. In the absence of these factors, pancreatic cancer incidence rates among blacks probably would not exceed those among whites of either sex.     

Place matters: variation in the black/white very preterm birth rate across U.S. metropolitan areas, 2002-2004

OBJECTIVE: We reported on the distribution of very preterm (VPT) birth rates by race across metropolitan statistical areas (MSAs). METHODS: Rates of singleton VPT birth for non-Hispanic white, non-Hispanic black, and Hispanic women were calculated with National Center for Health Statistics 2002-2004 natality files for infants in 168 MSAs. Subanalysis included stratification by parity, age, smoking, maternal education, metropolitan size, region, proportion of MSA that was black, proportion of black population living below the poverty line, and indices of residential segregation. RESULTS: The mean metropolitan-level VPT birth rate was 12.3, 34.8, and 15.7 per 1,000 live births for white, black, and Hispanic women, respectively. There was virtually no overlap in the white and black distributions. The variation in mean risk across cities was three times greater for black women compared with white women. The threefold disparity in mean rate, and two- to threefold increased variation as indicated by standard deviation, was maintained in all subanalyses. CONCLUSION: Compared with white women, black women have three times the mean VPT birth risk, as well as three times the variance in city-level rates. The racial disparity in VPT birth rates was composed of characteristics that were constant across MSAs, as well as factors that varied by MSA. The increased sensitivity to place for black women was unexplained by measured maternal and metropolitan factors. Understanding determinants of differences in both the mean risk and the variation of risk among black and white women may contribute to reducing the disparity in risk between races.     

Pre-pregnancy stress reactivity and pregnancy outcome

Stress has been proposed as a cause of preterm birth (PTB) and small-for-gestational age (SGA), but stress does not have the same effects on all women. It may be that a woman's reaction to stress relates to her pregnancy health, and previous studies indicate that higher reactivity is associated with reduced birthweight and gestational age. The objective of this study was to examine the relationship between pre-pregnancy cardiovascular reactivity to stress and pregnancy outcome. The sample included 917 women in the Coronary Artery Risk Development in Young Adults Study who had cardiovascular reactivity measured in 1987-88 and at least one subsequent singleton livebirth within an 18-year period. Cardiovascular reactivity was measured using a video game, star tracing and cold pressor test. Gestational age and birthweight were based on the women's self-report, with PTB defined as birth <37 weeks' gestation and SGA as weight <10th percentile for gestational age. Linear and Poisson regression and generalised estimating equations were used to model the relationship between reactivity to stress and birth outcomes with control for confounders. Few associations were seen between reactivity and pregnancy outcomes. Higher pre-pregnancy diastolic blood pressure (adjusted relative risk 1.14; 95% confidence interval [CI] 0.98, 1.34) and mean arterial pressure reactivity (1.15; 0.98, 1.36) were associated with risk of PTB at first pregnancy, while SGA was associated with lower systolic blood pressure reactivity (0.76; 0.60, 0.95). No associations were seen with other measures of reactivity. Contrary to hypothesis, the association between heart rate reactivity and PTB in first pregnancy was stronger in whites (adjusted relative risk 1.39; 1.03, 1.88) than in blacks (1.00; 0.83, 1.20; P for interaction = 0.08). Similar results were found for mean arterial pressure. No strong associations were found between higher pre-pregnancy stress reactivity and SGA or PTB, and stress reactivity did not have a stronger association with birth outcomes in blacks than whites.     

The Prevalence of Socioeconomic and Behavioral Characteristics and their Impact on Very Low Birth Weight in Black and White Infants in Georgia

Objectives: We examined possible reasons for the disparity in the rate of very low birth weight (VLBW) delivery (<1500 g) in the United States between black women and white women. Methods: Using data from a population-based, case–control study of very low birth weight infants, we compared the prevalence of sociodemographic and behavioral characteristics between black and white mothers of normal birth weight infants; the difference in these characteristics between case and control mothers; and, using logistic regression, calculated odds ratios for VLBW for black versus white infants, adjusting for these characteristics. Results: Although black women were disadvantaged on every variable examined, they did not report more behavioral risk factors. Among white women, several traditional risk factors were associated with VLBW, while among black women, only marital status, cigarette smoking, and vitamin nonuse were associated with VLBW delivery. Controlling for the socioeconomic and behavioral factors reduced the odds ratio for VLBW delivery among black mothers from 3.7 to 3.3. Conclusions: Racial disparity in socioeconomic status may be greater than our current ability to adjust for it in epidemiologic studies. The fact that traditional risk factors were not associated with VLBW delivery in black women may be due to the very high prevalence of these risk factors among black women or to different or additional risks or stresses experienced by black women.     

Comparison of cardiovascular risk factors in obese blacks and whites

Blacks are known to have higher blood pressure levels, a higher prevalence of hypertension, and higher body weights than whites. However, the interrelationships of these and other cardiac risk factors have not been analyzed in an obese population. We compared blood pressure (BP) and lipid levels in 174 obese blacks and 939 obese white patients who were entering a weight loss program; we also assessed the effects of weight loss on these factors. Prevalence of treated hypertension was similar in blacks and whites (28% vs. 25%, respectively). In patients not taking BP medication, black women weighed more (108 kg) than white women (102 kg) and black and white males' weights were similar (135 kg vs. 131 kg). Systolic and diastolic BP were similar in black and white women; black males had similar SBP but a significantly lower DBP than white males (83 mmHg vs. 89 mmHg, respectively). Lipid levels were similar in black and white women except black women had lower triglycerides (1.30 mmol/L) than white women (1.58 mmol/L, p < 0.05); and black males compared to white males had significantly lower total cholesterol (4.76 mmol/L vs. 5.56 mmol/L), LDL-cholesterol (3.15 mmol/L vs. 3.52 mmol/L) and triglycerides (1.31 mmol/L vs. 2.17 mmol/L, p < 0.05). Adult-onset obesity adversely affected a number of cardiovascular risk factors in whites, but not in blacks. Blacks lost significantly less weight (-13 kg) than whites (-19 kg). However, controlling for the difference in weight loss, blacks sustained comparable improvement in lipids and blood pressure, except for TC/HDL-C (whites improved significantly more, -0.36 kg/m2, than blacks, 0.03 kg/m2). Thus, the impact of obesity on cardiovascular risk factors seems ameliorated in blacks compared to whites.     

Cardiovascular disease risk factors and mortality among black women and white women aged 40-64 years in Evans County, Georgia

There have been few prospective studies of the epidemiology of cardiovascular disease in women, especially black women. The authors report the 20-year mortality experience of 391 black and 549 white women aged 40-64 years recruited in 1960-1961 into the Evans County Cardiovascular Study. The vital status of 98.9% of the white women and 96.2% of the black women had been determined as of May 1, 1980. Using Cox' proportional hazards model, the authors estimated that black women had a 70% excess risk of cardiovascular disease mortality compared with white women, unadjusted for any risk factors. At entry, black women had higher systolic blood pressure, higher Quetelet index, lower serum cholesterol, lower social status, and similar age distribution and prevalence of cigarette smoking compared with white women. Cardiovascular disease mortality was significantly associated with systolic pressure in all women, serum cholesterol in white women, and Quetelet index in low social status white women. Adjustment for cardiovascular disease risk factors and social status explained most of the difference in cardiovascular disease mortality between blacks and whites.     

Parental age difference and adverse perinatal outcomes in the United States

This study was undertaken to examine the relationship between paternal and maternal age differences and adverse perinatal outcomes in the United States. Data were obtained on singleton pregnancies delivering at >or=20 weeks gestation in the United States in 1995-97 from the National Center for Health Statistics data sets. Adverse perinatal outcomes that were evaluated included fetal death rate (>or=20 weeks), preterm delivery <37 weeks and small-for-gestational-age (SGA) births (birthweight <10th centile for gestational age and corrected for sex). Age difference was defined as paternal minus maternal age. The analysis included 8995274 pregnancies (11.3% blacks, 88.7% whites). An increase in fetal death rate, preterm delivery and SGA births was noted among white women who were older than their male partners. For black mothers older than their partners, there was an increase in fetal death rate when the women were <20 years old, but a decrease in fetal death rate when >35 years old. Neither rates of preterm delivery nor SGA births were increased much for black women with varying parental age differences. This demonstrates that race and maternal age both contribute to the effects of parental age difference on adverse perinatal outcomes.     

Comparing biological measurements of vitamin C, folate, alpha-tocopherol and carotene with 24-hour dietary recall information in nonhispanic blacks and whites.

PURPOSE: To assess intake of several vitamins in preparation for a large cohort study investigating the effect of diet on risk of colon and prostate cancer. METHODS: The dietary intake of several vitamins were assessed using eight different 24-hour recalls and a 200-item food frequency questionnaire (FFQ) from each subject. Participants also attended a clinic where blood was drawn and body composition, weight, height, and blood pressure were measured. A total of 97 black and 96 nonhispanic white subjects participated. The levels of alpha-tocopherol, carotene, folate, and vitamin C in the blood were correlated with the dietary intakes as measured by both 24-hour recalls and FFQ. RESULTS: Correlations between blood levels and energy-adjusted dietary intake assessed by 24-hour recalls (with supplements) were as follows: carotene (adjusted for serum cholesterol): 0.47 and 0.55 in black and white subjects, respectively; alpha-tocopherol (adjusted for serum cholesterol): 0.61 (blacks) and 0.50 (whites); vitamin C: 0.22 (blacks) and 0.17 (whites); folate: 0.54 (blacks) and 0.55 (whites). Correlations between blood levels and FFQ indices were smaller in magnitude: 0.34 and 0.28 for carotene in black and white subjects, respectively, 0.37 and 0.56 for alpha-tocopherol (adjusted for serum cholesterol), 0.20 and 0.03 for vitamin C and 0.24 and 0.32 for folate. CONCLUSIONS: The correlations observed were generally of modest to moderate size and were similar to or larger than those reported by others. This is despite variations in absorption, metabolism, and excretion of the vitamins and suggests that both the 24-hour recalls and the FFQ contain valid information.     

Application of the time-series approach to assess the temporal trend of racial disparity in chlamydia prevalence in the US National Job Training Program

The authors applied a time-series approach to assess the temporal trend of racial disparity in chlamydia prevalence between young, socioeconomically disadvantaged blacks and whites entering the US National Job Training Program. Racial disparity was defined as the arithmetic difference between age group-, specimen type-, and region of residence-standardized chlamydia prevalences in blacks and whites. A regression with autoregressive moving average errors model was employed to adjust for serial correlation. Data from 46,849 women (2006-2008) and 136,892 men (2004-2008) were analyzed. Racial disparity significantly decreased among women (by an average of 0.122% per 2-month interval; P < 0.05) but not among men (-0.010%, P = 0.57). Chlamydia prevalence significantly declined for black women (-0.139% per 2-month interval; P = 0.004), black men (-0.045%, P < 0.001), and white men (-0.035%, P = 0.002) but not for white women (-0.028%, P = 0.413). Despite the decreases among black women and black men, the black-white disparities remained high for both sexes; in 2008, the racial disparity was 8.1% (95% confidence interval: 6.8, 9.3) for women and 9.0% (95% confidence interval: 8.4, 9.6) for men. These findings suggest that current chlamydia control efforts may be reaching young black men and women but need to be scaled up or modified to address the excess risk among blacks.     

Institutional racism,neighborhood factors,stress, and preterm birth

Objective. Racial/ethnic disparities in the risk of preterm birth may be explained by various factors, and previous studies are limited in examining the role of institutional racism. This study focused on the following questions: what is the association between preterm birth and institutional racism as measured by residential racial segregation (geographic separation by race) and redlining (black–white disparity in mortgage loan denial); and what is the association between preterm birth and reported stress, discrimination, and neighborhood quality.

Design. We used data from a clinic-based sample of pregnant women (n = 3462) participating in a stress and pregnancy study conducted from 1999 to 2004 in Philadelphia, PA (USA). We linked data from the 2000 US Census and Home Mortgage Disclosure Act (HMDA) data from 1999 to 2004 and developed measures of residential redlining and segregation.

Results. Among the entire population, there was an increased risk for preterm birth among women who were older, unmarried, tobacco users, higher number of previous births, high levels of experiences of everyday discrimination, owned their homes, lived in nonredlined areas, and areas with high levels of segregation measured by the isolation index. Among black women, living in a redlined area (where blacks were more likely to be denied mortgage loans compared to whites) was moderately associated with a decreased risk of preterm birth (aRR = 0.8, 95% CI: 0.6, 0.99).

Conclusion. Residential redlining as a form institutional racism and neighborhood characteristic may be important for understanding racial/ethnic disparities in pregnancy and preterm birth.     

The relationship of interpregnancy interval to infant birthweight and length of gestation among low-risk women, Georgia

To examine the association between interpregnancy interval and low birthweight (< 2500 g), preterm delivery (< 37 weeks' gestation), and inadequate fetal growth, we studied a population-based sample of 23 388 white and 4885 black women at low risk for adverse pregnancy outcomes who delivered their first and second infants in Georgia from 1980 to 1992. We used fetal death and livebirth certificates. The interpregnancy interval was the time from delivery to the woman's next conception. For each pregnancy outcome, we stratified by race and used logistic regression to assess the association between interpregnancy interval and outcome, while controlling for confounders. Intervals <6 months were observed for 3.7% of white women and 7.0% of black women and intervals 48 months were seen for 16.8% of white women and 24.8% of black women. Results from logistic regression showed that, for both races, interpregnancy interval was associated with low birth-weight and preterm delivery. Nearly all of the increased risk occurred in intervals < 6 months or 48 months. The magnitude of the increase in risk associated with these intervals ranged from modest to moderate and was similar for black and white women. Because short interpregnancy intervals are rare and are weak risk factors among low-risk women, efforts to lengthen interpregnancy intervals are unlikely to reduce substantially their rates of adverse pregnancy outcomes.     

Neighborhood socioeconomic status,maternal race and preterm delivery: a case-control study

PURPOSE: To explore associations between neighborhood socioeconomic context and preterm delivery, independent of maternal and family socioeconomic status, in African-American and white women. METHODS: A case-control study of African-American (n = 417) and white (n = 1244) women delivering infants at the University of California, San Francisco's Moffitt Hospital, between 1980 and 1990. RESULTS: Neighborhood socioeconomic contexts were associated with preterm delivery but associations were non-linear and varied with race/ethnicity. For African-American women, living in a neighborhood with either high or low median household income was associated with an increased risk of spontaneous preterm delivery, as was living in a neighborhood with large increases or decreases in the proportion of African-American residents during the study decade. Residence in neighborhoods with high and low rates of male unemployment was associated with a decreased risk of preterm delivery. Among white women only large positive and negative changes in neighborhood male unemployment were associated with risk of preterm delivery. CONCLUSIONS: Neighborhood factors and changes in neighborhoods over time are related to preterm delivery, although the mechanisms linking local environments to maternal risk remain to be specified.     

The NICHD Women's Contraceptive and Reproductive Experiences Study: methods and operational results

PURPOSE: This paper presents methods and operational results of a population-based case-control study examining the effects of oral contraceptive use on breast cancer risk among white and black women aged 35-64 years in five U.S. locations. METHODS: Cases were women newly diagnosed with breast cancer during July 1994 through April 1998. Controls were identified through random digit dialing (RDD) using unclustered sampling with automated elimination of nonworking numbers. Sampling was density-based, with oversampling of black women. In-person interviews were conducted from August 1994 through December 1998. Blood samples were obtained from subsets of cases and controls, and tissue samples were obtained from subsets of cases. A computerized system tracked subjects through study activities. Special attention was devoted to minimizing exposure misclassification, because any exposure-disease associations were expected to be small. RESULTS: An estimated 82% of households were screened successfully through RDD. Interviews were completed for 4575 cases (2953 whites; 1622 blacks) and 4682 controls (3021 whites; 1661 blacks). Interview response rates for cases and controls were 76.5% and 78.6%, respectively, with lower rates for black women and older women. CONCLUSIONS: The methodologic details of this large collaboration may assist researchers conducting similar investigations.     

Racial disparity in risk of preterm birth associated with lower genital tract infection

The objective of this study was to examine the associations between lower genital tract infection, racial group and preterm birth in the Vaginal Infections and Prematurity Study, a large prospective cohort study conducted between 1984 and 1989. This analysis included 11 910 women enrolled at 23-26 weeks' gestation with equal representation from self-identified African American, Hispanic and white women. Subjects were screened for Chlamydia trachomatis, Trichomonas vaginalis and bacterial vaginosis at study entry, and their pregnancy outcomes were ascertained after delivery. The primary outcome of interest was preterm delivery of a low-birthweight infant (<37 weeks and <2500 g). The associations between lower genital tract infection and preterm delivery of a low-birthweight infant were examined within each racial group, with adjustment for potential confounders using multivariable logistic regression. In this cohort, 6.4% of African Americans, 3.8% of Hispanics, and 4.4% of whites had a preterm delivery of a low-birthweight infant (P < 0.001). Lower genital tract infection was significantly associated with preterm delivery of a low-birthweight infant among African Americans, but not among other racial groups. The proportion of preterm birth associated with lower genital tract infection was 21% among African Americans and 5% among whites. The increase in infection-associated preterm birth among African Americans appears to be related both to an increased prevalence of lower genital tract infection, and also to an increased risk of preterm delivery of a low-birthweight infant in the context of lower genital tract infection.     

Racial/ethnic disparities in injection drug use in large US metropolitan areas

PURPOSE: Because blacks and Latinos bear a disproportionate burden of injection-related health problems compared with whites, we sought to describe black/white and Latino/white disparities in injecting drugs in 94 US metropolitan statistical areas (MSAs) in 1998. METHODS: Using US Census data and three databases documenting injectors' use of different healthcare services (drug treatment, HIV counseling and testing, and AIDS diagnoses), we calculated database-specific black/white and Latino/white disparities in injecting in each MSA and created an index of black/white and Latino/white disparities by averaging data across the three databases. RESULTS: The median black/white injecting disparity in the MSAs ranged from 1.4 to 3.7 across the three databases; corresponding median Latino/white injecting disparities ranged from 1.0 to 1.1. Median black/white and Latino/white index disparity values were 2.6 and 1.0, respectively. CONCLUSIONS: Although whites were the majority of injectors in most MSAs, database-specific and index black/white disparity scores indicate that blacks were more likely to inject than whites. While database-specific and index disparity scores indicate that Latinos and whites had similar injecting rates, they also revealed considerable variation in disparities across MSAs. Future research should investigate these disparities' causes, including racial/ethnic inequality and discrimination, and study their contributions to the disproportionate burden of injection-related health problems borne by blacks and Latinos.     

Preterm birth subtypes among blacks and whites.

The differences in preterm birth between blacks and whites are poorly understood. Our study examined subtypes of moderately preterm delivery (34-36 completed weeks of gestation) and very preterm delivery (20-33 weeks) in blacks and whites using North Carolina birth certificate data for 1988-1989. We divided the causes of preterm birth into three categories: preterm premature rupture of the membranes, indication of pregnancy complication, and idiopathic preterm deliveries. The overall prevalence of preterm birth was 8.0% and 16.7% for whites and blacks, respectively. The entire gestational age distribution of blacks was shifted to earlier ages relative to whites. More highly educated blacks still had higher risks of moderately and very preterm deliveries than less educated whites. Multivariate analysis, controlling for other factors, showed that blacks had 3.3, 2.5, and 3.5 times the risk of whites to have preterm premature rupture of the membranes, complication-related, and idiopathic delivery, respectively, among very preterm births, and 1.6, 1.9, and 2.0 times the risk of whites for moderately preterm births of the same three types.