Study design
WEST, RECRUITMENT
This pilot trial used a randomised, parallel group design with 1:1 allocation, nested within an observational cohort study. Women in the observational cohort had all requested OptiBreech care. This design was chosen for two reasons. Firstly, it enabled identification of preliminary safety outcomes among a larger cohort of women planning a VBB with OptiBreech care, some of whom may not be eligible for or may not consent to randomisation. Secondly, we anticipated that the larger cohort may host multiple nested randomised trials in the future, to increase the efficiency of delivering trials within this population [The setting was four NHS Hospitals in England. Sites were chosen based on their recruitment rate and fidelity to protocol performance in the OptiBreech 1 observational study of planned VBBs [The study was funded by the UK National Institute for Health and Care Research (NIHR, 300582) and sponsored by King’s College London. Ethics approval was obtained from the West London & GTAC Research Ethics Committee (21/LO/0808, 19 November 2021). The pilot trial was prospectively registered with the ISRCTN (14521381, 18 October 2021).