A serious adverse event in human drug trials is defined as any untoward medical occurrence that at any dose Results in death Is life-threatening Requires inpatient hospitalization or causes prolongation of existing hospitalization Results in persistent or significant disability/incapacity May have caused a congenital anomaly/birth defect Requires intervention to prevent permanent impairment or damageThe term "life-threatening" in the definition of "serious" refers to an event in which the patient was at risk of death at the time of the event; it does not refer to an event which hypothetically might have caused death if it were more severe. Wikipedia