Cost-effectiveness of a randomized controlled trial comparing low-dose aspirin to placebo for the prevention of recurrent preterm birth

To assess the cost-effectiveness of low-dose aspirin compared to placebo for the prevention of recurrent preterm birth from a healthcare perspective. This was a cost-effectiveness analysis alongside a multicenter, randomized, double-blinded, placebo-controlled trial. We included women with a singleton pregnancy and a previous spontaneous preterm birth <37 weeks of gestation of a singleton. Women were randomized between aspirin 80 mg daily and placebo, initiated between 8 and 16 weeks of gestation. We estimated the difference in preterm births (<37 weeks of gestation), and maternal and neonatal healthcare costs using seemingly unrelated linear regression analyses. Bootstrapping was performed to estimate statistical uncertainty. A total of 387 women were included: 194 in the aspirin group and 193 in the placebo group. We observed a small, statistically non-significant difference in preterm birth (21.2% vs. 25.4%; risk difference -4.3%; 95% CI: -12.7% to 4.1%) and healthcare costs (mean -<euro>99; 95% CI: -<euro>2385 to <euro>2325) in the aspirin group compared to placebo. The cost-effectiveness acceptability curve showed that the probability of aspirin being cost-effective was 54% for a willingness to pay threshold of <euro>0 for one prevented preterm birth and 78% for <euro>50 000 for one prevented preterm birth. Our findings suggest that aspirin is the dominant strategy over placebo for the prevention of preterm birth. However, there was substantial uncertainty around the results and definite conclusions regarding the cost-effectiveness of aspirin cannot be drawn.