This document summarizes a study that examined the relationship between the drug domperidone, which is commonly used off-label to stimulate lactation, and the risk of ventricular arrhythmia and mortality during the postpartum period. The study used a retrospective cohort of over 225,000 women in British Columbia between 2002-2011. It found a possible doubling of the risk of hospitalization for ventricular arrhythmia among those exposed to domperidone, though the results were not statistically significant. Larger studies are needed to confirm any association.