Fibrinolytic and Antifibrinolytic Activity in Pregnancy

Abstract

Fibrinolytic activity and serum antifibrinolysin were estimated in normal pregnant women, during and after labour.The decreased fibrinolytic activity found during labour returned to non-pregnant levels within 24 hours of delivery. During the same period, the serum antifibrinolysin was rapidly diminished.It is suggested that the post-partum increase in fibrinolytic activity to non-pregnant levels is due to alterations in the fibrinolytic system itself, as well as to changes in circulating antifibrinolysin.In a previous communication alterations in fibrinolytic activity during pregnancy were reported (Gillman, Naidoo, and Hathorn, 1959). It was shown that, within 13 to 15 weeks of the onset of pregnancy, fibrinolytic activity, as measured by euglobulin lysis time, was greatly reduced and remained so until the second stage of labour. Within 24 hours of delivery, there was a rapid increase in fibrinolytic activity, control levels being attained within 24 hours. These findings, using another method and in another racial group, were in agreement with the findings of Biezenski and Moore (1958).However, the mechanism underlying these changes remains obscure. Whether the alteration in fibrinolytic activity during pregnancy is a function of fibrinolysin and/or precursors, antilysins, fibrin substrate, or a combination of these factors, is not known. To this end, serum antifibrinolytic activity was determined in nine pregnant African women, both during and after labour. Materials and MethodsPregnant African women in the first and second stage of labour were selected from the labour wards of the King Edward VIII Hospital. They were all medically healthy and obstetrically normal. In each of the women, determinations were made-during labour and nine to 24 hours after parturition.Collection of Blood.-The subjects were not under basal conditions. All blood samples were collected between 9 and 10 a.m. through a wide-bore needle inserted by clean venipuncture into the antecubital vein. The first few drops were discarded and 5 ml. of the freely flowing blood was collected in clean 1Ox70 mm. tubes containing 0.5 ml. of a 3.8% sodium citrate solution. The tubes were immediately placed in melting ice and transported to the laboratory.

Defibrination in Normal and Abnormal Parturition

“…The fall and recovery of fibrinogen and factors V and VIII thus appear to be independent of changes in blood volume and to reflect changes in concentration during the immediate puerperium. The fibrinolytic activity, as indicated by the euglobulin lysis time, decreases in late pregnancy, increascs sharply in the first 24 hr postpartum, then returns to pre-existing lcvcls (Guest, 1954;Naidoo et al, 1960;Shaper et al, 1966). We have corroborated thcsc findings but our additional data indicate that twin births do not show this phenomenon, decreased fibrinolytic activity being noted throughout the 24 hr period.…”

Studies on Fibrinolytic Inhibitors During Pregnancy

“…Opinions differ also about the plasminogen level during pregnancy. Thus Shaper et al (27) and Brakman (4) found no difference between the plasminogen levels in pregnant and nonpregnant women, while Naidoo et al (19) found them to be low during pregnancy. Most authors have, however, reported high values of plasminogen during pregnancy (15, 18, 20, 22).…”

“…The spontaneous fibrinolytic activity in the blood is substantially reduced during pregnancy (2, 3, 4, 13, 20,27). The mechanism of this relatively low fibrinolytic activity in pregnancy is, however, still obscure, some workers ascribing it to an increased content of inhibitors in the blood (2, 13, 14, 18,19,22); and others, to a decreased production or release of plasminogen activators from the vessel walls (3, 4,20,28). This lack of unanimity is accentuated by the fact that some authors did not find any increase in inhibitors (1, 5 , 23).…”