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A study has been undertaken in 72 women to provide systematic information on the changes that occur in a wide range of haemostatic variables during and after pregnancy. Factors VII, VIII:C, VIIIR:Ag, X, fibrinogen and alpha 1-antitrypsin, rose markedly throughout pregnancy. Factors II and V and alpha 2 macroglobulin all rose early on but then decreased steadily. Antithrombin III:C and Ag fell slightly. There was a marked decrease in fibrinolytic activity from 11-15 weeks onwards. Levels of fibrin degradation products rose from 21-25 weeks onwards. The rise in coagulation factors that occurs could be due to increased synthesis or increased activation by thrombin, or to both. The findings are consistent with a mild degree of local intravascular coagulation from early on in pregnancy in some women.
Stirling et al. (Sun,) studied this question.