An amniotic fluid embolism (AFE) is a rare childbirth (obstetric) emergency in which amniotic fluid, fetal cells, hair, or other debris enters the mother's blood stream via the placental bed of the uterus and triggers an allergic-like reaction. This reaction then results in cardiorespiratory (heart and lung) collapse and massive hemorrhaging (coagulopathy). It was first formally characterized in 1941. While it is rare (between 1 in 8000 and 1 in 80,000 deliveries), the high mortality makes it the fifth most common cause of maternal mortality in the world, in some estimates.