Sample size calculation
PPH
RECRUITMENT
With a primary feasibility outcome of 85% of randomized participants receiving IP, 58 participants were required to achieve reasonable precision in the estimate of the primary outcome (95% CI 73.2–93%). Assuming approximately 4000 yearly deliveries at SHSC and an estimated recruitment rate of 5%, we estimated that this number of participants could be recruited in approximately 4 months. If feasible within the allotted time frame, this would have allowed for recruitment of 3408 patients, providing 80% power to detect a 35% relative risk reduction in PPH (6.1–4%), over approximately 2 years in a full, multi-centre trial, including affiliated centres from the Greater Toronto Area Obstetrical (GTA-OBS) Research Network (~ 65,000 deliveries/year).