595 Low-dose aspirin for preterm birth prevention in low-risk mothers by race

Our group and others have shown that low dose aspirin (LDA) decreases spontaneous preterm birth (sPTB) in low risk parturients. Our objective was to examine whether this relationship was modified by race. This is a secondary analysis of a randomized clinical trial examining LDA for preeclampsia prevention in nulliparous, low-risk women. The parent trial defined low risk as the absence of pre-existing hypertension or other medical comorbidities. Women received 60mg LDA or placebo between 13-25 weeks. In our study, multiple gestations, fetal anomalies, and terminations or abortions <20 weeks were excluded. Our exposure, race, was self-reported in the parent trial and categorized as non-Hispanic White, Hispanic, non-Hispanic Black, and Other. The primary outcome was sPTB <34 weeks; secondary outcomes included sPTB <37 weeks and all PTB <37 and <34 weeks. We fit logistic regression models to examine how LDA modified the relationship between race and PTB adjusting for confounders. We then performed sensitivity analyses to compare rates of PTB by race in the LDA and placebo groups. 2528 of 3171 original participants were included. 16.8% (425) were White, 32.4% (819) Hispanic, and 50% (1265) Black, and 0.8% (19) were Other. Baseline characteristics differed between racial groups, including maternal age, BMI, education level, marital status, tobacco and alcohol use, and gravidity. The rate of sPTB <34 was significantly higher in Black women (2.8%) compared to White (1.2%) and Hispanic women (1.2%) (p=0.04). Logistical regression showed no differential effect of LDA by race; Black race was no longer an independent risk factor for sPTB <34 (aOR 1.71 [95% CI 0.67, 4.40]). A similar pattern was found for sPTB <37 and PTB <34 and <37 weeks (Table 1). In our sensitivity analyses, sPTB <34 differed by race in the placebo group (p=0.01) but did not differ in the LDA group (p=0.90, Figure 1). LDA mitigated racial disparities in sPTB and decreased sPTB <34 weeks. LDA should be considered as a strategy for sPTB prevention.View Large Image Figure ViewerDownload Hi-res image Download (PPT)