An amniotic fluid embolism (AFE) is a very uncommon childbirth (obstetric) emergency in which amniotic fluid enters the blood stream of the mother, triggering a serious reaction, which results in cardiorespiratory (heart and lung) collapse and massive bleeding (coagulopathy). The rate at which it occurs is 1 instance per 20,000 births and it comprises 10% of all maternal deaths. This condition is unpredictable and no risk factors have been verified. From Wikipedia
