Poverty, Education, Race, and Pregnancy Outcome

David A. Savitz, University of North Carolina at Chapel Hill
Jay S. Kaufman, University of North Carolina at Chapel Hill
Nancy Dole, University of North Carolina at Chapel Hill
Anna Maria Siega-Riz, University of North Carolina at Chapel Hill
John M. Thorp, Jr., University of North Carolina at Chapel Hill
Diane Kaczor, University of North Carolina at Chapel Hill

Despite much research on racial and socioeconomic disparities in perinatal health, few studies have considered the potential for differing impact of socioeconomic variables among racial subgroups. In seeking causes for the disadvantage in pregnancy outcome measures of African-Americans relative to Whites, some aspect of socioeconomic status is often invoked as an underlying cause, given the marked socioeconomic differences between African-Americans and Whites resulting from America's long history of racial segregation and discrimination. However, among the most ostensibly comparable groups of highly educated women, for example, substantial racial disparities in outcome remain. While lower social class, income, and education are generally associated with increased risks of preterm birth, the impact of socioeconomic position may well vary across racial groups because the indices used to define socioeconomic status could reflect different attributes or experiences for African-Americans compared to Whites. We were particularly interested in examining the joint effects of low educational status and poverty in relation to preterm birth and growth restriction among African-American and White women. We assessed patterns of preterm birth and fetal growth restriction by race, education, and income (poverty index), using data from the Pregnancy, Infection, and Nutrition (PIN) Study, a prospective cohort study of preterm birth in central North Carolina. Women were recruited from university medical center prenatal care clinics as well as from a county health department. The 2926 enrolled African-American and White women were analyzed to evaluate the relation between socioeconomic status and preterm birth (<37 weeks' gestation) and small-for-gestational-age (SGA) (<10th percentile of weight for age) using binomial regression. Using vital records to compare pregnancies among all women residing in the geographic area from which the majority of PIN Study participants were recruited, African-American and White study participants were younger, less educated, and less often married, but African-American study participants had a lower risk of preterm birth (12.1 percent versus 17.5 percent) while White participants had a similar risk to White women in the area (10.6 percent versus 9.9 percent). These deviations between the study participants and women in the area were largely a function of their source of prenatal care and not a reflection of non-response. In multivariate models adjusted for age and parity, highly educated African-American participants had an increased risk of preterm birth associated with poverty status (relative risk (RR) = 1.55, 95% CI: 1.12--2.15) with little impact of poverty among African-American women with lower education. Only White participants with both low education and low income were at increased risk of preterm birth (RR = 1.69, 95% CI: 1.07--2.67), with no impact of either low education or poverty alone. Regardless of educational level, poverty among White women was associated with an increased risk of SGA (RRs of 1.56-1.68), with no effect of education observed. Among African-Americans, neither education or poverty or their combination was associated with risk of SGA births. Among the PIN Study participants, the patterns of association with education and income were complex, with less of an effect overall among African-Americans compared to Whites, and an elevated risk of preterm birth for African-American women with higher education and lower income. This complex pattern of joint effects of education and poverty may reflect in part the differing material and psychological implications of education and income status differ between groups. For example, the combination of higher education and poverty among African-Americans may be associated with increased risk due to the incongruity in failing to realize the economic benefits of more education. Whites may more readily realize the benefits associated with advanced education than African-Americans, e.g., income, medical care, housing opportunities. The inconsistencies in pattern of association across socioeconomic indices (education, poverty), pregnancy outcome measure (preterm birth, SGA), and racial group (African-Americans, Whites) undoubtedly reflect in part imprecision and peculiarities of our study population, but may also point towards the inadequacy of models that presume consistent social or biological implications of these indices across racial groups.