Development of the usefulness tool
We search in Medline and Google Scholar (March 2021) using the terms ‘Usefulness’ and ‘Randomised Controlled Trial’ to identify items that are important to assess usefulness in clinical research. Of the 15,473 results we identified only one paper highlighting usefulness of clinical research itself (other identified papers commented on usefulness of an intervention studied in the trial). This identified paper on usefulness, elaborated on eight specific criteria. (5) These eight features were then discussed within a steering group consisting of two epidemiologist (PB, JI) and four clinicians working in the field of obstetrics and gynaecology (JH, ZA, MO, BWM). After discussion and consent of all group members, a usefulness criteria appraisal checklist consisting of eight criteria combining 13 items was developed (Box S2).