Maternal Age Patterns of Preterm Birth: Exploring the Moderating Roles of Chronic Stress and Race/Ethnicity

Despite the suggested contribution of cumulative chronic stress to the racial/ethnic disparities in preterm birth (PTB), it is unclear how chronic stress, maternal age, and race/ethnicity are linked underlying PTB.

We investigated the moderating effect of chronic stress on the maternal age-PTB association among non-Hispanic (N-H) White, N-H Black, Hispanic, and Asian women.

We analyzed the Washington State's Pregnancy Risk Assessment Monitoring System data linked with birth certificates. The sample included women aged 18 years or older who birthed the first, singleton baby without birth defects. Chronic stress was measured by race/ethnicity-specific chronic stress indices. A maternal age-chronic stress interaction was modeled to predict PTB by logistic regression stratified by race/ethnicity. In subanalysis, the moderating role of racism was investigated in the maternal age-chronic stress interaction among three minority groups combined.

Women's maternal age trajectory of PTB varied by their race/ethnicity and chronic stress level. N-H White and N-H Black women showed a steeper maternal age-related increase in PTB (weathering) under higher chronic stress, indicating a chronic stress' cumulative effect with maternal age. Besides, the extent of weathering was amplified by racism on top of chronic stress, particularly among N-H Black women.

These results show that both chronic stress and racism may develop accelerated PTB risk among minority women. Future research should use more objective and accurate chronic stress measures to ascertain the complex relationships among chronic stress, racial discrimination, and maternal age underlying the racial/ethnic differentials in PTB.