The pressing need to reduce the racial disparities in infant mortality, low birth weight, and preterm birth in the United States has led to new theories and new research directions on the pregnancies of African-American women (Hogue and Vasquez, 2002; Rich-Edwards et al., 2001; Rowley, 1994, 2001; Rowley et al., 1993). In particular, attention is being directed to the role of racism and discrimination in health outcomes in general (Krieger, 2000) and in pregnancy outcomes specifically (Collins et al., 2000, 2004). Racism is defined as racially motivated interpersonal and institutional discrimination (Krieger, 2000). Several research teams have developed self-report measures of racism, and these measures have been used in a handful of case-control and prospective studies of pregnancy. Collins and colleagues (2000) published the first study on this issue with a sample of low-income African-American women in Chicago who delivered very-low-birth-weight infants (n = 25), all of which were preterm, or matched controls with infants of normal birth weight (n = 60). They used Krieger's measures developed for the CARDIA study (Krieger, 1990; Krieger and Sidney, 1996). These measures query participants about their experiences of racism at work, at school, when getting medical care, when receiving service at stores or restaurants, and when finding housing. Mothers with infants with very low birth weights were twice as likely to report experiences of racial discrimination during pregnancy as women who delivered infants of normal birth weight. After adjustment for socioeconomic condition, levels of social support, cigarette smoking, alcohol intake, and illegal drug use, the adjusted OR was 3.2.

Four subsequent studies have been published since publication of the first one by Collins et al. (2000), two of which had case-control designs (Collins et al., 2004; Rosenberg, 1965) and two of which had prospective designs (Dole et al. 2003; Mustillo et al., 2004). Mustillo and colleagues (2004) examined racial discrimination using the CARDIA data set, which included data from a 10-year prospective study of a large cohort of African-American and white men and women. Their sample comprised the 352 African-American and white women who gave birth to live infants at 20 weeks gestation or longer. Racism was measured by use of the Krieger measure at year 7 of the study, and low birth weight for an intervening pregnancy was assessed by self-report at year 10. Several findings are of interest. First, race was a risk factor for preterm birth, as expected (OR = 2.54); but the risk estimate was reduced after adjustment for lifetime experiences of racism, suggesting that racism may mediate the racial-ethnic difference in preterm birth rates. Smoking, alcohol intake, depression, and the amount of weight gained during pregnancy did not have such effects. Second, women who had experienced lifetime discrimination were nearly five times more likely to deliver a low-birth-weight infant than those who had not experienced racism. This relationship was reduced by including preterm birth in the model, suggesting that the effect of discrimination on birth weight was as a result of the effects of racism on the likelihood of an earlier delivery. Thus, lifetime experiences of racism explained the racial and ethnic disparities in the rates of both preterm birth and low birth weight.

Collins and colleagues (2004) also considered lifetime exposure to racism as well as pregnancy exposure in a case-control study of 104 African-American women in Chicago who delivered very-low-birth-weight preterm infants and 208 matched controls who delivered normal-birth-weight infants. Lifetime exposure to racial discrimination in three or more domains of life was associated with very low birth weight (OR = 3.2; OR = 2.6 adjusted for age, education, and cigarette smoking). The outcomes were not associated with perceived prenatal racial discrimination. The authors conducted post-hoc tests, whose results suggested that the effects detected were not attributable to recall bias because of infant illness among the low-birth-weight infants. In addition, the strongest risk was for college-educated African-American women. Collins and colleagues (2004) conclude that "lifelong accumulated experiences of racial discrimination by African-American women constitute an independent risk factor for preterm delivery" (p. 2132). One apparent pathway whereby racism appears to influence health and possibly prenatal processes is by cardiovascular functioning (Krieger, 1990; Krieger and Sidney, 1996). (For a complete review of the literature on racial and ethnic disparities in pregnancy outcomes, definitions and measures of racism, the conceptualization of racism as stress, and findings, see the work of Giscombe and Lobel [2005]).

The following are key questions to be resolved in future research: Is racism a risk factor for preterm birth or fetal growth restriction or both, and, if so, by what pathways? Does racism act in association with other factors, such as social class, age, medical risk factors, or other stress or emotional factors to pose a risk? If racism is a potent risk factor, are there effective, practical, and cost-effective ways to mitigate its effects on maternal and infant outcomes?

In general, the emerging literature on racism and preterm delivery suggests that racism may be a potent stressor throughout the lifetimes of African-American women that contributes to an explanation of the racial and ethnic disparities in the rates of both preterm birth and low birth weight. However, further study is needed to replicate and extend the existing studies. One challenge researchers face is the difficulty of assessing experiences of racism. Many factors contribute to underreporting of the experience. This challenge requires further precise work by investigators in future.

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