Amniotic fluid embolism.

Amniotic fluid embolism is the most unpredictable and catastrophic complication of pregnancy, accounting for 10% to 20% of maternal deaths. The pulmonary edema commonly seen in this syndrome is probably due primarily to alveolar capillary leakage and may be potentiated by high maternal extracellular volume, low colloid osmotic pressure, and, in some patients, by depressed myocardial function. In patients in whom resuscitation is successful, diuresis leads to rapid resolution of pulmonary edema. Amniotic fluid does not ordinarily enter the maternal circulation, and the identification of large numbers of fetal squames in the postpartum pulmonary microvasculature is probably of clinical significance.