A step in another direction: Looking for maternal genetic and environmental effects on racial differences in birth weight

To advance research on birth weight differences between black and white infants, it may be useful to study maternal effects. These effects present a set of risk factors that are largely unrelated to those that are presently under investigation and fail to explain the gap in birth weight; empirical findings suggest their involvement. Although maternal effects can be environmental, as illustrated by recent findings, genetic effects could be important as well because gene frequencies are known to differ across the "racial" groups as studied by birth weight researchers, and maternal genes can exert a causal effect on birth weight.     

Racial differences in birth health risk: A quantitative genetic approach

In the United States the gap between black and white babies' birth weights has remained largely unexplained. Rather than trying to measure all relevant variables, we used a genetically informative design to study the relative importance of genetic and environmental factors. Employing multiple indicators of "birth health risk," we found that the racial differences increased with the magnitude of the shared environmental effects. This suggested that possible genetic effects would not pertain to fetal genes, although genes affecting the mother's physical or physiological characteristics could be important because they contribute to shared environment in our analysis.     

Racial differences in infant mortality by cause of death: The impact of birth weight and maternal age

This research examines racial disparities in infant mortality, overall and separately according to cause of death. Using linked birth and death records for the 1975 cohort of live births in Florida, racial differences are initially described and then explained statistically as a product of the distribution of births by birth weight and maternal age. The impact of birth weight is more pronounced than is the effect of maternal age. The analysis suggests the potential utility of examining infant mortality separately by cause of death. Based on the findings, we argue for systematic research focused on factors affecting birth weight.     

Comment on “compromised birth outcomes and infant mortality among racial and ethnic groups”

Frisbie, Forbes, and Pullum (1996) show that it is meaningful to account for low birth weight, preterm delivery, and intrauterine growth-retardation when analyzing differences in compromised birth outcomes and infant mortality among racial and ethnic groups. I compare their findings for the 1987 U.S. birth cohort with findings for the 1988 U.S. birth cohort, using linked birth and infant death vital statistics from the National Center for Health Statistics. I focus on their calculation of fetal growth curves, which are highly at odds with the curves commonly used in the obstetric and pediatric literature. I compare birth outcome distributions and infant death probabilities using Frisbie et al. 's method and other standards. I conclude that Frisbie et al. 's method is not suited for the study of intrauterine growth-retardation at the population level because of the major flaws in gestational age measurement that exist in the type of data they use. An appropriate alternative is to apply a standard of normal intrauterine growth derived from antenatal estimation of fetal weight-for-gestational-age to the vital statistics data.     

Bayesian analysis of an econometric model of birth inputs and outputs

This study offers a simultaneous equations model of the birth process with seven endogenous variables: four birth inputs (maternal smoking, maternal drinking, first trimester prenatal care, and maternal weight gain) and three birth outputs (gestational age, birth length, and birth weight). The data are taken from the National Longitudinal Survey of Youth. Our analysis conditions on twenty-nine exogenous variables including four racial dummies to account for the widely cited racial differences in birth outputs. We find that there is sizeable correlation between the disturbances in the four input and three output equations and among output disturbances, and that results from our simultaneous equations model are substantially different from those using the single-equation approach. It appears that the High/Low Risk Birth Weight Puzzle remains unresolved under our modeling framework.All correspondence to Kai Li. The authors gratefully acknowledge the research support of the Social Sciences and Humanities Research Council of Canada, and helpful comments on an earlier draft by the editor (Junsen Zhang), two anonymous referees, Sid Chib, Kei Hirano, John Geweke, Gary Koop, seminar participants at the University of Alberta, the University of California at Irvine, University of Kansas, University of Minnesota, Queen Mary College of University of London, Washington University at St. Louis, and participants of the 2001 Winter Meetings of the Econometric Society in New Orleans. We are solely responsible for any errors contained herein. Responsible editor: Junsen Zhang.     

Business Cycles,Medicaid Generosity,and Birth Outcomes

Birth outcomes influence many aspects of later life health and wellbeing, making healthcare access during pregnancy a policy priority. Low-income mothers often depend on Medicaid, for which eligibility is determined by their income relative to state eligibility thresholds. The prevalence of adverse birth outcomes is known to exhibit cyclical variation, due in part to changes in the composition of women giving birth in response to changing economic conditions. However, cyclical variation in adverse birth outcomes also varies with respect to Medicaid eligibility thresholds. Our analysis uses birth-records data for 2000 through 2013, aggregated into 173,936 county-by-quarter observations and linked to county-level unemployment rates and state-level parental Medicaid thresholds. Using fixed-effects negative binomial models, we examine the role of Medicaid generosity in influencing birth outcomes across business cycles. We test for interactions between Medicaid and unemployment, hypothesizing that the negative effects of recessions are worse where Medicaid thresholds are more restrictive. We find that higher Medicaid generosity dampens the negative effects of recessions on birth outcomes. The extent to which Medicaid interacts with unemployment also varies according to the age and race composition of mothers; in particular, Black mothers are both most affected by unemployment and most responsive to Medicaid generosity. Given current concerns about racial gaps in both infant and maternal mortality, our findings suggest that Medicaid may be an important feature of a strategy to close gaps in the prevalence of adverse birth outcomes across racial groups, especially during bust years.     

Skin Color and Intelligence in African Americans: A Reanalysis of Lynn's Data

Finding a modest yet statistically significant correlation between skin tone and vocabulary test scores among African Americans, Lynn (2002) concludes that intelligence in African Americans is significantly determined by the proportion of Caucasian genes (p. 365). In this reanalysis of Lynn's data, I demonstrate that his bivariate association disappears once childhood environmental factors are considered. Therefore, a genetic link between skin color and intelligence among African Americans cannot be supported in his data. Investigators seeking to establish a genetic connection between racial ancestry and intelligence must move beyond simple bivariate results to address the confounding influence of environmental conditions that affect cognitive development.     

IQ, Birth Weight, and Number of Sexual Partners in White, African American, and Mixed Race Adolescents

Mean levels of three characteristics—verbal IQ, number of sexual partners, and birth weight—were examined in African American, White (European-descent) Americans, and Black/White mixed race American adolescents. The sample came from Wave 1 of the National Longitudinal Study of Adolescent Health. The mean age was 16 years. According to their interviewers, the mixed race children had an African American physical appearance. The African American adolescents had a lower birth weight, a lower verbal IQ, and a higher number of sexual partners than did White adolescents. For each characteristic, the mixed race mean fell between the means of the two parental populations. Design extensions were proposed that include: (1) directly genotyping for individual racial admixture, (2) including parents of the mixed race children, and (3) including their cousins.     

An investigation of racial and ethnic disparities in birth weight in Chicago neighborhoods

We examine differences in the mean birth weights of infants born to non-Hispanic black, non-Hispanic white, and Mexican-origin Hispanic mothers (of any race) in Chicago in 1990 using linear regression models with neighborhood fixed effects. Our pooled models accounted for 64% of the black-white difference and 57% of the black/Mexican-origin Hispanic difference. Differences in the relationship between measured characteristics and birth weight accounted for around half the birth-weight gap between non-Hispanic black and other infants. Efforts to close this gap must go beyond programs that aim to reduce the level of risk factors among black women to address the causes of differences in the effects of risk factors.     

Race and exits from white collar jobs: Differences in downward mobility processes among African American, Latino, and White males

Does race affect the route to downward mobility from white collar occupations? Data from Panel Study of Income Dynamics are used to assess the minority vulnerability thesis, which maintains there are race-specific processes of down ward occupational mobility among males from white collar occupations. Findings indicate that, consistent with theory, a racialized continuum exists across six years of the work-career. For Whites, the path to downward mobility is relatively narrow and structured by traditional stratification-based causal factors, namely, human capital, back ground socioeconomic status, and job/labor market characteristics. For African Americans, the route to downward mobility is broad-based and not captured by traditional stratification factors and Latinos occupy an intermediate ground between Whites and African Americans. Further, as predicted by theory, the racial gap in mobility processes between Whites and racial minorities is pronounced at the lower-tier of white collar employment. Finally, implications of the findings for understanding labor market inequalities on the basis of race are discussed.     

Is the Association Between Education and Fertility Postponement Causal? The Role of Family Background Factors

A large body of literature has demonstrated a positive relationship between education and age at first birth. However, this relationship may be partly spurious because of family background factors that cannot be controlled for in most research designs. We investigate the extent to which education is causally related to later age at first birth in a large sample of female twins from the United Kingdom (N = 2,752). We present novel estimates using within–identical twin and biometric models. Our findings show that one year of additional schooling is associated with about one-half year later age at first birth in ordinary least squares (OLS) models. This estimate reduced to only a 1.5-month later age at first birth for the within–identical twin model controlling for all shared family background factors (genetic and family environmental). Biometric analyses reveal that it is mainly influences of the family environment—not genetic factors—that cause spurious associations between education and age at first birth. Last, using data from the Office for National Statistics, we demonstrate that only 1.9 months of the 2.74 years of fertility postponement for birth cohorts 1944–1967 could be attributed to educational expansion based on these estimates. We conclude that the rise in educational attainment alone cannot explain differences in fertility timing between cohorts.     

Low birth weight in Aboriginal babies--a need for rethinking Aboriginal women's pregnancies and birthing

Low birth weight in Aboriginal babies has become a persistent quandary as their average birth weight continues to be lower than that of non-Aboriginal babies. Arguments, reviews and research abound to explain this difference which is deemed unacceptable and needing resolution. A précis review of current theories and findings around low birth weight in Aboriginal babies is presented as a background for much needed alternative considerations of this issue. The low birth weight dilemma requires urgent rethinking of Aboriginal women's experiences and feelings of their pregnancies and possible effects on their unborn babies. There is a critical need for empowerment of Aboriginal women that goes beyond rhetoric and dominant ideologies about what is best for them and their babies, and genuinely enables them to assume control and self-determinism in ways that might make a significant difference, including importantly to their babies’ birth weights.     

Birth Cohort and the Specialization Gap Between Same-Sex and Different-Sex Couples

We examine differences in household specialization between same-sex and different-sex couples within and across three birth cohorts: Baby Boomers, Generation X, and Generation Y. Using three measures of household specialization, we find that same-sex couples are less likely than their different-sex counterparts to exhibit a high degree of specialization. However, the “specialization gap” between same-sex and different-sex couples narrows across birth cohorts. These findings are indicative of a cohort effect. Our results are largely robust to the inclusion of a control for the presence of children and for subsets of couples with and without children. We provide three potential explanations for why the specialization gap narrows across cohorts. First, different-sex couples from more recent birth cohorts may have become more like same-sex couples in terms of household specialization. Second, social and legal changes may have prompted a greater degree of specialization within same-sex couples relative to different-sex couples. Last, the advent of reproductive technologies, which made having children easier for same-sex couples from more recent birth cohorts, could result in more specialization in such couples relative to different-sex couples.     

Absolute Change in Cause-Specific Infant Mortality for Blacks and Whites in the US: 1983–2002

This paper examines absolute change in infant mortality from 5 leading causes of death for whites and blacks over a 20 year period. Change in infant mortality varies by cause, race, and birth weight. Absolute decline in mortality from respiratory distress syndrome (RDS) and sudden infant death syndrome (SIDS) in the overall study population has been more rapid for black infants during the period after specific technological innovations were approved and behavioral practices were recommended for these conditions. For low birth weight infants, blacks experienced greater decline in mortality from SIDS and whites experienced greater decline in RDS mortality. Despite remarkable declines in mortality from these causes, relative racial disparities have increased over this time period. For the overall study population, blacks and whites experienced similar rates of mortality decline from congenital anomalies. Mortality decline from this cause among low birth weight infants occurred at a faster pace for whites. Mortality from causes for which no specific innovations were developed increased for blacks but remained relatively constant for whites. An analysis of absolute change complements the relative disparities approach by revealing the dynamics of change, thus providing a more complete understanding of changing racial disparities in infant mortality.     

Birth Outcome Measures and Infant Mortality

Recent studies have proposed alternative birth outcome measures as means of assessing infant mortality risk; nevertheless, there hasn’t yet been an integrated analysis of these approaches. We review 14 strategies, including various combinations of birth weight, gestational age, fetal growth rate, and Apgar scores—as predictors of early neonatal, late neonatal, and postneonatal mortality, and infant mortality. Using the NCHS linked birth/infant death file for 2001, we construct multivariate logit models and assess the associations between each of the 14 key birth outcome measures and four mortality outcomes. We find that all evaluated birth outcome measures are strong predictors, but Apgar scores are the strongest among all models for all outcomes, independent of birth weight and gestational age. Apgar scores’ predictive power is stronger for Mexican-, white-, and female-infants than for black- and male-infants. Second, all birth outcome measures remain significantly associated with mortality, but their predictive power reduces drastically over time. These findings suggest a rule of thumb for predicting infant mortality odds: when available, Apgar scores should always be included along with birth weight (or LBW status) and gestational age. Additionally, these findings argue for the continued study of low birthweight, gestational age, and Apgar scores as independently salient health outcomes.     

Neighbourhood Ethnic Density Effects on Behavioural and Cognitive Problems Among Young Racial/Ethnic Minority Children in the US and England: A Cross-National Comparison

Studies on adult racial/ethnic minority populations show that the increased concentration of racial/ethnic minorities in a neighbourhood—a so-called ethnic density effect—is associated with improved health of racial/ethnic minority residents when adjusting for area deprivation. However, this literature has focused mainly on adult populations, individual racial/ethnic groups, and single countries, with no studies focusing on children of different racial/ethnic groups or comparing across nations. This study aims to compare neighbourhood ethnic density effects on young children’s cognitive and behavioural outcomes in the US and in England. We used data from two nationally representative birth cohort studies, the US Early Childhood Longitudinal Study-Birth Cohort and the UK Millennium Cohort Study, to estimate the association between own ethnic density and behavioural and cognitive development at 5 years of age. Findings show substantial heterogeneity in ethnic density effects on child outcomes within and between the two countries, suggesting that ethnic density effects may reflect the wider social and economic context. We argue that researchers should take area deprivation into account when estimating ethnic density effects and when developing policy initiatives targeted at strengthening and improving the health and development of racial and ethnic minority children.     

Genetic Bio-Ancestry and Social Construction of Racial Classification in Social Surveys in the Contemporary United States

Self-reported race is generally considered the basis for racial classification in social surveys, including the U.S. census. Drawing on recent advances in human molecular genetics and social science perspectives of socially constructed race, our study takes into account both genetic bio-ancestry and social context in understanding racial classification. This article accomplishes two objectives. First, our research establishes geographic genetic bio-ancestry as a component of racial classification. Second, it shows how social forces trump biology in racial classification and/or how social context interacts with bio-ancestry in shaping racial classification. The findings were replicated in two racially and ethnically diverse data sets: the College Roommate Study (N = 2,065) and the National Longitudinal Study of Adolescent Health (N = 2,281).     

Residential segregation in American cities: A contrary review

Clark (1986) has reviewed evidence on the causes of racial residential segregation in American cities and has concluded that economic factors, job locations, preferences, and information bear the predominant explanatory weight; private acts of housing discrimination carry little weight. This article argues that Clark's conclusions are erroneous because they are based on a selective and incorrect interpretation of the evidence available to him and because more recent studies provide strong evidence to the contrary.     

Residential segregation in American cities: A contrary review

Clark (1986) has reviewed evidence on the causes of racial residential segregation in American cities and has concluded that economic factors, job locations, preferences, and information bear the predominant explanatory weight; private acts of housing discrimination carry little weight. This article argues that Clark's conclusions are erroneous because they are based on a selective and incorrect interpretation of the evidence available to him and because more recent studies provide strong evidence to the contrary.     

The Black Gender Gap in Educational Attainment: Historical Trends and Racial Comparisons

It is often asserted that the gender gap in educational attainment is larger for blacks than whites, but historical trends comparing the black and white gender gap have received surprisingly little attention. Analysis of historical data from the U.S. census IPUMS samples shows that the gender gap in college completion has evolved differently for whites and blacks. Historically, the female advantage in educational attainment among blacks is linked to more favorable labor market opportunities and stronger incentives for employment for educated black women. Blacks, particularly black males, still lag far behind whites in their rates of college completion, but the striking educational gains of white women have caused the racial patterns of gender differences in college completion rates to grow more similar over time. While some have linked the disadvantaged position of black males to their high risk of incarceration, our estimates suggest that incarceration has a relatively small impact on the black gender gap and the racial gap in college completion rates for males in the United States.