Background/Purpose: Systemic lupus erythematosus (SLE) and rheumatoid arthritis (RA) are independently associated with preterm birth (PTB). Black women have higher risk of both ARD and PTB; however, few studies have examined race/ethnic disparities in PTB risk among women with SLE or RA. In a large multiethnic cohort of women, we examined race/ethnic disparities in PTB risk stratified by ARD type (SLE or RA) as well as the interaction between race/ethnicity and ARD type.

Methods: Birth records linked to hospital discharge data of singleton births in California from 2007 to 2012 were leveraged for a retrospective cohort study including women at least 18 years old diagnosed with either SLE or RA identified by the international classification of diseases (ICD), ninth revision. 222 women with both SLE and RA were excluded from analysis. Race/ethnicity (Asian, Black, Hispanic, and White) was abstracted from the birth certificate. The relative risk of PTB (< 37 weeks versus ≥37 weeks gestation) was compared among race/ethnicity and stratified by ARD type (RA or SLE). Results were adjusted for relevant covariates including maternal age, pre-pregnancy body mass index (BMI), insurance, education, country of origin, parity and smoking using Poisson regression with the log link function. In the model we examined all possible combinations of comparisons by race and ethnicity by altering the referent group in the model. Additionally, we identified differences in the racial/ethnic disparities in PTB risk between RA and SLE by including an interaction term to the model between race/ethnicity and ARD (RA versus SLE).   

Results: A total of 2,309 with RA and 2,874 women with SLE were included in the analysis.  In women with SLE, Black, Hispanic, and Asian women were ~1.3 to 1.5 times more likely to have PTB compared to White women (Table 1). Black, Hispanic, and Asian women with SLE did not significantly differ from each other in PTB risk. Black women with RA were ~1.6 to 2.4 times more likely to have PTB compared to either Asian, Hispanic, or White women. Asian, Hispanic, and White women with RA did not significantly differ from each other in PTB risk. When examining the interaction between race and ARD (RA versus SLE) the Black-White PTB risk disparity in women with RA was 1.5 times higher compared to the Black-White PTB risk disparity in women with SLE (Table 1). The Black-Hispanic PTB risk disparity in women with RA was 2.1 times higher compared to the Black-Hispanic PTB risk disparity in women with SLE. The Black-Asian PTB risk disparity in women with RA was 1.5 times higher compared to the Black-Asian PTB risk disparity in women with SLE, but this did not quite reach statistical significance (p< 0.05).

Conclusion: Our findings in this large multiethnic cohort of women are consistent with prior work demonstrating that race/ethnicity is associated with increased relative risk of PTB but indicate that some disparities differ between RA and SLE. Black-White, Black-Hispanic, and Black-Asian disparities in PTB risk were greater in women with RA compared to women with SLE. This information may provide important public health information for addressing racial disparities, particularly in women with RA. 

Association of race with preterm birth stratified by ARD diagnosis

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ACR Meeting Abstracts - https://acrabstracts.org/abstract/racial-and-ethnic-disparities-in-the-risk-of-preterm-birth-among-women-with-systemic-lupus-erythematosus-or-rheumatoid-arthritis-with-varying-reference-groups/