Calcium chloride for the prevention of uterine atony during cesarean delivery: A pilot randomized controlled trial and pharmacokinetic study

•This pilot randomized controlled trial protocol was feasible.•A one-gram dose of dilute calcium chloride was well-tolerated by recipients.•Peak ionized calcium was 1.6 mmol/L, clearance 0.9 L/min and distribution volume 76 L.•Uterine atony occurred in 20% of calcium recipients and 50% of placebo recipients.•Intravenous calcium warrants study as a preventive therapy for uterine atony.