Inclusion Criteria:  Patient had a trial of labor for vaginal delivery prior to cesarean Patient received an oxytocin infusion for labor augmentation or induction prior to cesarean  Exclusion Criteria:  renal dysfunction with serum Cr >1.0 mg/dL known underlying cardiac condition treatment with digoxin within the last 2 weeks for a maternal or fetal indication treatment with a calcium channel blocker medication within 24 hours hypertension necessitating intravenous antihypertensive medication within 24 hours emergent case in which study participation could in any way impede patient care by the judgement of the obstetrician, anesthesiologist, or bedside nurse