Amniotic Fluid Embolism:

Latest Concepts and Current Research

This site is intended to provide background on Amniotic Fluid Embolism and give readers information about on-going research about this leading cause of maternal mortality in developed countries.

 

Background

Amniotic Fluid Embolism, AFE, was first described in 1926 by a Brazilian physician.[1]  The first English language discussion of the disease (and the name for the disease) came from two papers published in the same issue of the Journal of the American Medical Association in 1941.[2]  A study of eight maternal deaths at the University of Chicago Lying-in hospital for women found that all eight had substantial amounts of fetal cells in the blood vessels of the mothers’ lungs.  This material appeared to be blocking the flow of blood through the lungs back to the heart, apparently explaining the sudden demise of these women during labor.

            After these first descriptions, the illness grew in notoriety.  Although rare, AFE, kills and maims suddenly and unpredictable.  It preys on the most vulnerable population—pregnant women and their fetuses.  The symptoms are spectacular and generally fall into one of four categories:

            1)   cardiovascular collapse characterized by falling blood pressures and a rising pulse culminating in cardiac arrest

            2)   respiratory distress with increasing difficulty in breathing sometimes concluding with a respiratory arrest

            3)   disordered blood clotting.  The specific medical terms for this condition include coagulopathy and disseminated intravascular coagulation (DIC).

            4)  neurological symptoms such as seizures or coma

            Since AFE can be highly mortal, some perspective on maternal mortality rates is in order.  In developed nations, the rate is on the order of 5-10 women per 100,000 pregnancies.  In developing nations, the maternal mortality rate reflects the death rate before the advent of modern medicine and is on the order of 1,000 per 100,000 pregnant women.  It is important to note, that the risk of death in the third world of 1 in 100 applies to each new pregnancy such that the cumulative risk from having multiple pregnancies is substantially higher than a death rate of 1%.  Another grim statistic is that maternal mortality rates generally correspond to infant mortality rates by country.  It should be noted that starvation, epidemics, and warfare can increase maternal death rates to 10% or even higher.

            The causes of death vary between developed and developing countries.   While AFE appears to be equally infrequent throughout the world, it assumes greater importance as a cause of death in nations with good medical care that drives the overall maternal mortality rate down to 10 per 100,000 pregnancies.  In these countries, AFE ranks between the first and third leading cause of death, depending on surveillance methods and how investigators assign the cause of death.  For instance, AFE commonly causes maternal hemorrhage.  Is such a maternal death counted as an embolic event or blood loss?  In any event, with roughly 3,000,000 births in the US each year and 300 maternal deaths, one can surmise that between 50 and 100 of these deaths will result from AFE.

            Any disease that is potentially mortal general injures far more than it actually kills.  Many, certainly not all, mothers that survive AFE suffer permanent injury.  Brain injury is common among those who survive respiratory distress and hysterectomy (removal of the uterus) is often a treatment for maternal hemorrhage.  If AFE occurs before delivery, fetal injury or death is also commonplace.



[1] Meyer JR.  Embolia pulmonary amnio caeosa.  Brasili-Medico.  1926.  2:  301-3.

[2] Steiner PE, Lushbaugh CC.  Maternal pulmonary embolism by amniotic fluid as a cuase of obstetric shock and unexpected death in obstetrics.  JAMA.  1941.  117: 1245-54, 1340-45.