Objective To assess the cost-effectiveness of treatment with nifedipine compared with atosiban in women with threatened preterm birth. Design An economic analysis alongside a randomised clinical... Show moreObjective To assess the cost-effectiveness of treatment with nifedipine compared with atosiban in women with threatened preterm birth. Design An economic analysis alongside a randomised clinical trial (the APOSTEL III study). Setting Obstetric departments of 12 tertiary hospitals and seven secondary hospitals in the Netherlands and Belgium. Population Women with threatened preterm birth between 25 and 34 weeks of gestation, randomised for tocolysis with either nifedipine or atosiban. Methods We performed an economic analysis from a societal perspective. We estimated costs from randomisation until discharge. Analyses for singleton and multiple pregnancies were performed separately. The robustness of our findings was evaluated in sensitivity analyses. Main outcome measures Mean costs and differences were calculated per woman treated with nifedipine or atosiban. Health outcomes were expressed as the prevalence of a composite of adverse perinatal outcomes. Results Mean costs per patients were significantly lower in the nifedipine group [singleton pregnancies: euro34,897 versus euro43,376, mean difference (MD) -euro8479 [95% confidence interval (CI) -euro14,327 to -euro2016)]; multiple pregnancies: euro90,248 versus euro102,292, MD -euro12,044 (95% CI -euro21,607 to euro -1671). There was a non-significantly higher death rate in the nifedipine group. The difference in costs was mainly driven by a lower neonatal intensive care unit admission (NICU) rate in the nifedipine group. Conclusion Treatment with nifedipine in women with threatened preterm birth results in lower costs when compared with treatment with atosiban. However, the safety of nifedipine warrants further investigation. Tweetable abstract In women with threatened preterm birth, tocolysis using nifedipine results in lower costs when compared with atosiban. Show less