Low Dose Aspirin Increases Live Birth Rate Differentially along Socioeconomic Status

INTRODUCTION: Low socioeconomic status (SES) is associated with adverse pregnancy outcomes such as preterm birth and low birth weight. Lower medical advice compliance and decreased access to health care contribute to these events in this population. In addition, some studies suggest that women of low SES may have greater difficulty achieving pregnancy, although mechanisms for this phenomenon are not known. Low-dose aspirin (LDA) has been shown to increase pregnancy and live birth rates in women with elevated inflammatory markers. Since low SES is also associated with chronic, low-level inflammation, we hypothesized that low-dose aspirin may also increase live birth and pregnancy rates in low SES women. METHODS: We performed a secondary analysis of The Effects of Aspirin in Gestation and Reproduction (EAGeR) Trial, a multisite, blockrandomized, controlled trial. 1228 women were randomly allocated to either 81mg of aspirin + 400mcg of folic acid (n=615) or placebo + 400 mcg of folic acid (n=613). Participants took the study medication for six menstrual cycles or until 36 weeks' gestation if pregnancy was achieved. For this analysis, women were stratified by socioeconomic measures, which included income (low, mid, high) and a combined grouping of education and income (low-low, low-high, high-low, high-high). The effect of LDA vs. placebo was then determined within each strata. RESULTS: LDA increased live birth rates (RR 1.23, 95% CI: 1.03, 1.45) in the high-income group compared to placebo and increased pregnancy rates (RR 1.23, 95%CI: 1.06, 1.42) in the high education-high income group compared to placebo. The low-education low-income group also demonstrated an increased pregnancy rate (RR 1.22, 95% CI: 1.02, 1.46) compared to placebo, but no effects were observed among the participants grouped by low income alone. DISCUSSION: Our analysis shows high SES women consistently benefited from LDA as demonstrated by increased pregnancy and live birth rates compared to placebo. Less consistent effects of LDA in low SES women were observed, and no significant benefit of LDA was observed in mid-SES groups. Differences in factors such as underlying health risk factors and medication compliance may contribute to the different effects of LDA by SES on reproductive outcomes.