The possible predisposing causes of difibrination in the pregnant woman are discussed. Coagulation profiles and qualitative and quantitative assessment of fibrinolytic activity during labor, delivery and the early puerperium in normal pregnancies are presented. These factors were also studied in patients with abruptio placentae and prolonged intrauterine fetal death and in women whose pregnancies were terminated with intraamniotic infusion of hypertonic saline or prostaglandin F2alpha. The findings suggest that a minor degree of physiologic defibrination develops during normal labor that is qualitatively similar to, but of much lesser magnitude than, the pathologic defibrination syndrome commonly associated with abruptio placentae or prolonged intrauterine fetal death. Some degree of defibrination occurs in women undergoing saline abortion, similar to that of women during normal parturition, but does not usually reach clinically significant levels. The coagulation changes seen during prostaglandin abortion suggest that a minor degree of defibrination occurs that is substantially less than that seen during saline abortion. The findings presented form a basis for the rational management of defibrination in the pregnant woman.