'Sense of impending doom' may signal AFE. (Warning Sign).

NEW YORK -- The mere thought of amniotic fluid embolism is enough to make many obstetricians break a cold sweat. Fatal more often than not, this rare complication of pregnancy is one that most obstetricians hope they never see.

"Keep your basic life-support certification active, because if you ever see an amniotic fluid embolism, your patient is going to need it," Dr. Gary D.V Hankins said at an ob.gyn. symposium sponsored by Columbia University and Sloane Hospital for Women.

The complication arises when amniotic fluid leaks into the central maternal circulation, usually during labor as a result of tears in the lower uterine segment. The presence of amniotic fluid in maternal vessels triggers a profound pulmonary artery spasm, usually within 30 minutes. This results in intracardiac shunting of blood from the right to the left side of the heart.

If the woman survives the hypoxia associated with this first phase, the condition will usually progress to complete vasospasm, particularly in the vessels serving the ventricles, leading to left ventricular failure and extreme pulmonary edema. Some patients have fulminant hemorrhage as the primary symptom, said Dr. Hankins, who is professor of obstetrics and gynecology, University of Texas, Galveston.

"There is intense vasoconstriction of every capillary bed in the body, resulting in pulmonary edema and congestive heart failure that squeezes down the central circulation, leading to seizures. These women often say they feel like they're going to die, a real sense of impending doom. If a woman in labor says something like this, take it very seriously because it is a real warning," he said.

Estimates of the incidence of amniotic fluid embolism (AFE) are in the range of 1 in 70,000-90,000 live births. "My belief is that the real frequency is more like 1 in 8,000-either that or I've just been decidedly unlucky in my career," said Dr. Hankins, who has seen several of these cases. When he asked the audience of roughly 300 clinicians if they had ever seen APE, approximately two-thirds of the hands went up.

The problem is that epidemiologically many APE cases may be lumped in with unexplained death during labor. Since the formal diagnosis of APE is usually made by autopsy, many cases may go unrecognized. The give-away autopsy finding is of fetal squamous cells and mucin in maternal vasculature and various organs, including the kidneys, liver, spleen, pancreas, and brain.