Research Day


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CONTEXT: In Kalamazoo today, infants of color are dying at four times the rate of white infants, and the black infant mortality rate in Kalamazoo County is nearly double that of the state and the nation. Unlike white families, where health improves as socioeconomic resources improve, among black families socioeconomic gains have marginal effects on maternal infant health. Both structural and interpersonal discrimination have been implicated as root causes of health inequity.

OBJECTIVE: The primary goal of this study is to assess the association of structural and interpersonal discrimination with stress and, ultimately, with birth outcome. The secondary goal was to compare exposure to interpersonal discrimination reported by women of color compared to white women, and the degree to which it predicts stress and birth outcomes.

STUDY DESIGN: This was a mixed methods prospective study conducted in Kalamazoo County, Michigan. Women were recruited from the postpartum floors of both delivering hospitals. Eligibility criteria included being Kalamazoo County resident, being English speaking and being medically cleared by medical staff. Of the 471 eligible women during the recruitment period (January, 2017 to September, 2017), 426 were approached and 300 consented to study participation. Medical records were abstracted for 298 and 8-week postpartum phone surveys were completed with 244 of the participants. The dependent variable, birth outcome, was operationalized as infant birthweight (grams). The primary independent variables were measured by socioeconomic status (structural discrimination) and by self-reported Experiences of Discrimination scale (Cronbach’s alpha 0.74) (interpersonal discrimination). Two variables measured stress: the Perceived stress scale short form (alpha 0.56) and the Vigilance scale (alpha 0.77). Race was measured based upon self-report. The covariate prior poor birth outcome (a key contributor to current birth outcome) and was included in the final model. Statistical analyses were conducted using Pearson Chi Square for bivariate analysis and linear regression for multivariate (two-sided statistical significance set at α<.05).

RESULTS: The 240 women with single gestation delivery who completed a survey had mean birthweights of 3468 grams (CI 3398, 3539) and 11 (4.8%) delivered a low birthweight infant (under 2500 grams). Women of color had significantly lower birthweight infants than white women, with means of 3273 grams and 3581 grams, respectively (p<.001). They were more than twice as likely to be low income (70.2% of color, 30.1% white, p<.001), but just as likely to have had a prior poor birth outcome. Women of color reported significantly higher prevalence of ongoing discrimination than white women across multiple circumstances including: being treated with less courtesy or respect (43.6% of color, 26.0% white, p=.005), being treated as if they were not smart (28.7% of color, 16.0% white, p=.018), receiving poorer service than others at restaurants or stores (22.3% of color, 12.3% white, p=.040), and being followed around in stores (16.0% of color, 4.1% white, p=.002). Summed into a discrimination index (0-30, where higher value reflects more discrimination), a simple regression revealed discrimination to be a significant predictor of birthweight (unstandardized coefficient -16.25 (CI -32.34, -0.16), p=.048). Although discrimination was significantly associated with both stress and vigilance, neither of these variables were significant predictors of birthweight, and so were not included in the final model. In the multivariable model, controlling for prior poor birth outcome, income was a significant predictor of birthweight (unstandardized coefficient -4.85 (CI -8.94, -0.76), p=.02), but self-reported interpersonal discrimination was not (unstandardized coefficient -12.75 (CI -28.65, 3.16), p=.116). Stratification by race did not change this outcome.

CONCLUSION: Women of color experience substantially higher levels of interpersonal discrimination compared to white women; a factor which, alone, is a significant predictor of both stress and of birthweight. But when both are taken into account, the structural inequity of poverty outweighs interpersonal discrimination in predicting poor birth outcomes

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