Purpose

Postpartum hemorrhage (PPH) is the leading cause of maternal morbidity and mortality worldwide. Up to 80% of PPH is caused by uterine atony, the failure of the uterine smooth muscle to contract and compress the uterine vasculature after delivery. Laboratory and epidemiological studies show that low extracellular and serum calcium levels, respectively, decrease uterine contractility. A pilot study performed by the investigators supports the hypothesis that intravenous calcium chloride is well tolerated and may have utility in preventing uterine atony. The proposed research will establish the relationship between uterine tone and calcium through a clinical trial with an incorporated pharmacokinetic and pharmacodynamic (PK/PD) study. In a randomized, placebo-controlled, double-blind trial, investigators will establish the effect of 1 gram of intravenous calcium chloride upon quantitative blood loss and uterine tone during cesarean delivery in parturients with high risk of uterine atony. Investigators will concurrently collect serial venous blood samples to measure calcium for PK/PD modeling in this pregnant study cohort. High-quality clinical research and development of novel therapeutics to manage uterine atony are critical to reduce the high maternal morbidity and mortality from PPH.