(939) Randomized trial of postpartum aspirin and impact on NT-proBNP as a marker of maternal health

Objective: To compare levels of NT-proBNP, a marker of cardiac dysfunction, and clinical outcomes in patients at risk of preeclampsia randomized to continuation of low-dose aspirin (LDA) or placebo for 6 weeks postpartum.

Study Design: This double-blinded randomized-controlled trial included patients at risk of preeclampsia randomized in a 1:1 fashion to LDA (81 mg) versus an identical-appearing placebo continued for 6 weeks postpartum (Table 1). The primary outcome was NT-proBNP levels at the postpartum visit. A sample size of 90 was required to detect a clinically significant difference in NT-proBNP between LDA and placebo with 80% power. A sample size of 110 subjects was planned due to anticipated loss to follow-up in the postpartum period. Pre-specified secondary outcomes were postpartum preeclampsia, eclampsia, hospital readmission, initiation or titration of blood pressure medications, and blood transfusion. The primary outcome was compared using the Wilcoxon rank sum test. Secondary outcomes are reported as counts (%) and were compared using Fisher’s exact test after adjusting for multiple testing using Bonferroni correction.

Results: From July 2023 to March 2024, 110 participants were randomly assigned to LDA (n=55) or placebo (n=55). Baseline demographics were similar between groups (Table 1). There was no difference in the primary outcome of NT-proBNP levels between groups (median (IQR), 36.5 ng/mL (36.0, 61.0) vs. 39.5 ng/mL (36.0, 74.0), p=0.49). Rates of postpartum preeclampsia in patients randomized to LDA vs. placebo (5.6% vs. 12.7%) were numerically but not statistically significantly lower, with similar rates of hospital readmission and bleeding complications (Table 2). There were no cases of postpartum eclampsia or blood transfusion. Adherence was higher in the LDA (75% vs. 69%) than the placebo group.

Conclusion: Continuation of LDA after delivery was not associated with decreased NT-proBNP levels compared to placebo. Additional studies powered to detect differences in maternal outcomes are needed to evaluate the role of LDA in the postpartum period.