The effects of racial density and income incongruity on pregnancy outcomes

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Abstract

This study shows that living in a better area reduces the risk of adverse pregnancy outcomes but, among African–American women, living in an area in which they are in a racial minority may increase the risk. Using the 1991 cohort of single infants born to African–American women in Chicago, we measured census tract socioeconomic status and defined women as having “positive income incongruity” if they lived in wealthier tracts than the average African–American woman of comparable education and marital status. We examined whether or not the effect of positive income incongruity differed according to whether or not African–American women lived in predominantly black, or mixed tracts. Among the women living in predominantly black census tracts, positive income incongruity was associated with a lower risk of low birth weight (odds ratio (OR)=0.91) and preterm delivery (OR=0.83). These effects were modest, but statistically significant for gestation (p-value=0.01). In contrast, among the women living in mixed tracts positive income incongruity was not associated with low birth weight (OR=1.04) or preterm delivery (OR=1.11). In mixed areas the expected benefits of positive income incongruity are completely offset by the racial density effect, suggesting that the positive effects of a better socioeconomic context may be countered for minority women by the adverse effects of racism or racial stigma.

Introduction

Low birth weight and preterm delivery are leading causes of infant mortality and morbidity (Paneth, 1995). The disparity in pregnancy outcomes between African–American and other racial/ethnic groups in the United States is a striking and persistent public health problem (Centers for Disease Control and Prevention, 2002). When looking at infant mortality within racial/ethnic groups, there is a clear socioeconomic gradient, with college-educated mothers having a lower risk than mothers with less education. But looking across racial/ethnic groups, even college-educated African–American women fare badly, only American Indian and Alaska Native women with less than a high school education do worse (National Center for Health Statistics, 1998). A large body of research focused on genetic, behavioral and medical causes of this inequality has shed little light on these inequalities. Although many risk factors for low birth weight and preterm delivery have been identified, such as cigarette smoking and maternal hypertension, known factors do not explain the racial/ethnic gap and increasingly researchers have begun to seek explanations in the social context of African–American women (Krieger, Rowley, Herman, Avery, & Phillips, 1993).

One important aspect of a person's social context is the neighborhood they live in. Interest in relationships between neighborhood characteristics and health has burgeoned in recent years and there is consistent empirical evidence that living in a poor neighborhood can be damaging to health (Pickett & Pearl, 2001). Variation in the quality of neighborhood environments is a result of the inequitable economic and class structure and the unequal distribution of resources in society. Poor neighborhoods are characterized by a higher prevalence of hazards to healthy pregnancy, such as reduced availability of healthy foods and presence of stressors, such as crime (Morland, Wing, Diez Roux, & Poole, 2002; Sampson, Raudenbush, & Earls, 1997). They also have fewer protective resources, like accessible prenatal care clinics (Cook, Selig, Wedge, & Gohn–Baube, 1999; Perloff & Jaffee, 1999) and have an increased prevalence of health-compromising behaviors, such as smoking during pregnancy (Pickett, Wakschlag, Rathouz, Leventhal, & Abrams, 2002).

Associations between neighborhood socioeconomic context, low birth weight and preterm delivery have been reported in several studies. In an ecological study based in Chicago, the percentage of infants weighing less than 2500 g rose as the median family income of the neighborhood fell (Collins & David, 1990). In multi-level studies that attempt to separate the effects of social context from those of individual socioeconomic status, women living in deprived neighborhoods appear, irrespective of their own socioeconomic status or class, to have a higher risk of low birth weight (Fang, Madhavan, & Alderman, 1999; Jarvelin et al., 1997; O’Campo, Xue, Wang, & Caughy, 1997; Pearl, Braveman, & Abrams, 2001; Roberts, 1997; Sloggett & Joshi, 1998) and of preterm delivery (Ahern, Pickett, Selvin, & Abrams, 2003; Kaufman, Dole, Savitz, & Herring, 2003; Pickett, Ahern, Selvin, & Abrams, 2002). In some studies, these associations are stronger for African–American women than for other racial/ethnic groups (Ahern et al., 2003; Kaufman et al., 2003; Pearl et al., 2001; Pickett, Ahern, Selvin, & Abrams (2002), Pickett, Wakschlag, Rathouz, Leventhal, & Abrams (2002)), although it is important to note that these studies also show that better neighborhood socioeconomic status has also been associated with better pregnancy outcomes among the white women.

If deprived neighborhoods are a risk factor for adverse pregnancy outcomes, then it is not surprising that African–American women might suffer the impact more than white women. Racial segregation is a persistent reality in the US (Williams & Collins, 2001) and African–American women are far more likely than white women to be living in poor neighborhoods. As far back as 1950, Yankauer found that areas of New York City with a high proportion of births to non-white mothers were characterized by high population density, unsanitary conditions, lack of recreational areas, high rents for poor housing and, of course, high rates of infant mortality (Yankauer, 1950). What is surprising, given these demographic realities, is a suggestion, in at least three studies, that pregnancy outcomes in African–American women may be better when they live in neighborhoods where they constitute the majority of the neighborhood population. Roberts found that residence in a predominantly African–American community was associated with a decreased risk of low birth weight among African–American women, and this association existed independently of a woman's own socioeconomic status (Roberts, 1997). Similarly, Fang and colleagues found that in racially segregated areas of New York City members of the dominant group had better rates of infant mortality than members of the minority racial group (Fang, Madhavan, Bosworth, & Alderman, 1998). Pickett, Ahern, Selvin, & Abrams (2002), Pickett, Wakschlag, Rathouz, Leventhal, & Abrams (2002) found that the risk of preterm delivery for African–American women increased in neighborhoods with a large ten-year decline in the percentage of African–American residents.

These studies suggest that the social networks of African–American women in a racist society may be strongest when they reside in areas where they are not in a racial minority. Exposure to structural and interpersonal racism is a deep-rooted and widespread source of acute and chronic stress for African–Americans (Clark, Anderson, Clark, & Williams, 1999; Williams, 1999). However, there is little empirical evidence that addresses women's exposure to racism in relation to pregnancy outcomes. One small study of low-income African–American women, found that women who thought they had been discriminated against during pregnancy had a higher risk of very low birth weight (<1500 g) (Collins, David, Symons, Handler, Wall, & Dwyer, 2000).

Another important point to consider is that absolute levels of affluence or poverty may be less important for health than relative inequalities (Wilkinson, 1996). Collins et al. reported that positive income incongruity, i.e., living in a more affluent neighborhood than expected, on the basis of individual factors, was associated with a decreased risk of very low birth weight in a population-based study in Chicago (Collins, Herman, & David, 1997).

In summary, there is evidence that higher neighborhood socioeconomic status might protect against poor pregnancy outcomes for African–American women. Yet women in these salutary circumstances are also more likely to be living in communities with fewer African–Americans, and this has been linked to increased risk of adverse outcomes. We were unable to identify any reports where these factors were studied simultaneously in a population-based design. We hypothesized that the protective effects of positive income incongruity would be evident in areas that were predominantly African–American and weakened in mixed residential areas. In other words, we sought to identify an interaction between the effects of income incongruity and racial density on pregnancy outcomes among African–American women.

Section snippets

Data sources

We investigated the interaction between racial density and positive income incongruity on pregnancy outcomes in the population-based cohort of all African–American women who gave birth to a single infant in the City of Chicago in 1991. Information on maternal characteristics and birth outcomes was obtained from the Illinois Department of Public Health Division of Vital Records. This data file also included the census tract of the mother's self-reported place of residence at the time of the

Results

The analytic sample consisted of 25,186 singleton infants, born to African–American mothers living in 668 census tracts in Chicago. Seventy-seven percent of women lived in predominantly (over 90%) African–American tracts and 23% lived in mixed tracts. Mixed tracts were more affluent than predominantly African–American, with median household incomes of $27,920 and $20,372, respectively.

Maternal characteristics varied as expected by racial density (Table 1). Mothers in predominantly

Discussion

Our results indicate the intricacy of associations between race, socioeconomic context, and experiences of minority racial/ethnic status in contemporary urban settings, and their effects on population health. We found that the beneficial effect of positive income incongruity on pregnancy outcomes of African–American women operated only so long as they lived in census tracts with over 90% African–American residents. Beyond that threshold of racial density positive income incongruity was not

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