The weathering hypothesis and stillbirth: racial disparities across the life span

Objective: Given that studies have consistently demonstrated increased risk of stillbirth with increasing maternal age as well as race-ethnic disparities in stillbirth, the primary research question is how stillbirth risks within and between race-ethnic groups change with age.Design: Using fetal death (stillbirth) and live birth data from the National Center for Health Statistics 2007-2014. We calculated crude stillbirth rates (per 1,000 deliveries). Using multivariable logistic regression, we calculated adjusted odds ratios (aOR) and 95% confidence intervals (CI) for stillbirth across age groups to examine disparities in stillbirth among non-Hispanic blacks (blacks) and non-Hispanic whites (whites).Results: Rates and risks of stillbirth increased as maternal age increased; however, the magnitude of risk varies by race-ethnicity. Compared to women less than 20, black women age 40+ had a risk of almost 3.5 times (aOR = 3.47, 95% CI = 3.24-3.70) whereas among white women age 40+, the risk was more than 2.5 times (aOR = 2.68, 95% CI = 2.55-2.82). The risk of stillbirth among blacks compared to whites increased, peaking at ages 30-34 (aOR = 2.64, 95% CI = 2.56-2.73). At age 35 and beyond, the disparity in risks declined.Conclusion: As age increased, the risk of stillbirth increased for both blacks and whites. Because the disparity in risk between blacks and whites did not continue to increase with age, stillbirth does not seem to reflect the weathering hypothesis as other perinatal outcomes do.