Comparative hemostatic protein alterations accompanying pregnancy and parturition

Pregnancy and parturition represent adaptive, physiological stress situations that elicit both blood coagulation protein changes and endocrine alterations. This paper briefly reviews the interrelationships of these responses by comparing the available data in several mammalian species including man, dog, cow, and pig. Hemostasis is an enzymatically controlled cascade process involving platelets and specific coagulation proteins that results in the formation of insoluble strands of fibrin. Although qualitatively similar in most mammals, quantitative differences exist in the circulating levels of individual coagulation proteins which may contribute towards the different rates of clot formation. In the late gestation stage of human pregnancy, significant increases are observed in the circulating biological activities of the coagulation factors VII, VIII:C, IX, and X. In the dog, the activities of factors VII and IX reach peak values in midpregnancy, while in the cow little or no changes are observed except for factor VII values which show a significant increase only around the time of parturition. These coagulation changes appear to be associated with fluctuations in circulating hormone values, particularly plasma estrogen. In human pregnancy, the circulating levels of fibrinogen, the precursor of fibrin, increase during the gestation period reaching maximum values during and immediately following parturition. In the dog and the cow two distinct increases in fibrinogen values are observed, the first in the midgestation period and the second in the immediate postparturition period. In the pig, fibrinogen values also rise significantly at parturition. Oral contraceptive studies in the human female have indicated that changes in circulating activities of coagulation proteins are hormonally influenced.(ABSTRACT TRUNCATED AT 250 WORDS)