Changes in blood coagulation and fibrinolysis during the puerperium

OBSTETRICS

Changes in blood coagulation and fibrinolysis during the puerperium JOHAN YGGE Goteborg, Sweden

During the puerPerium an increased incidence of thromboembolic complications is observed. However, the incidence during pregnancy is relatively low. It is therefore of interest to study the changes in blood coagulation and fibrinolysis in connection with delivery because these changes may be one of the factors which predispose to thrombosis. This work shows that one to 4 weeks before delivery, there was a significantly increased level of fibrinogen, Factor II, VII, and X activities (P&P test), Factor VIII, and plasminogen. The urokinase excretion in the urine was significantly diminished during this period. The first days after delivery, a rapid decrease in the number of platelets and in the level of fibrinogen, Factor VIII, and plasminogen was observed. During the same period, there was an increase in the antifibrinolytic activity and also a pronounced increase in the urokinase excretion. Later during the puerperium, a new increase in fibrinogen, plasminogen, and, in some cases, in Factor VIII occurred before normal values were· reached about 2 weeks post partum. Principally, the changes which were seen in the hemostatic mechanism during the puerperium were the same as those observed after extensive surgery. The
D u

pregnancy there is a gradual in-

nancy rs low. 18 • '14 On the other hand, dur-

crease 1n the concentration of Factor I

ing the puerperium the incidence is about

(fibrinogen), 4 · t:J, 11 • 23 • 2 "· 28 • 33 Factor VII (proconvertin)/· 14 • 27 Factor VIII (antihemophilic factor), 10 • 25 • n, 33 Factor IX (Christmas factor), 13 • 25 • 29 and Factor X (Stuart-Prower factor) . 1 ~; 20 ; :~ This increase in several coagulation factors during pregnancy has been thought to produce a hypercoagulable state in the sense that these changes may increase the risk of thrombus formation.-·-· nowever, the incidence of thromboembolic complications during preg-

three to four times greater than during the last period of pregnancy. 18 • 31 It is therefore of interest to study changes in blood coagulation and fibrinolysis during the puerperium in order to illustrate the dynamic changes in the hemostatic mechanism during this period. It is reasonable to believe that these changes are of importance as one of the etiologic factors in thrombus formation durmg the puerperium. The changes in some of the above-mentioned blood coagulation factors in the puerperium have been described earlier. It has been shown that there is a gradual nor-

R

r

N G

7

From the Department of Internal Medicine II, Uniuersity of Goteborg.

Volume liH Number 1

malization in the levels of Factor I, Factor VII, and Factor VIII about one to 2 weeks after delivery.~. 4• 23 • 24 • 32 As for changes in the fibrinolytic system during the puerperium, different results have been obtained, in part probably because of the use of different methods to measure parameters of the fibrinolytic system. A gradual increase in the plasminogen level was observed during pregnancy but after delivery a rapid decrease occurred. 20 • 24 The fibrinolytic activity, measured by the euglobulin lysis time method 22 • oo or by resuspended euglobulin on fibrin plates, 24 has been found to be much reduced during the last months of pregnancy but rapidly returns to nonpregnant values after delivery. The same changes were observed when the fibrinolytic activity was measured by the diluted plasma clot lysis time method. 8 • '10 Other authors have found an increased spontaneous caseinolytic activity of the euglobulin fraction of plasma during pregnancy and a rapid normalization after delivery. 20 The same discrepancies have been found in the literature with respect to the antiplasmin level during pregnancy and after delivery. Some authors have found that the antiplasmin activity increases during pregnancy and is rapidly normalized after delivery.20• 24 Other have not been able to confirm these observations.n, 12 Difierent r~.~sults have been obtained also with respect to blood inhibitors of urokinase-induced fibrinolysis.12• 24 The specific detem1ination of the two known inhibitors of plasmin in plasma, Le ., u 2-macroglobulin and a 1-ant1try"ps1n. has been performed during pregnancy and after delivery. 15 It has bt:'en shown that the a 1 -antitrypsin concentration increased considerable during pregnancy while the a 2 ruacrog1obu1in concentration increased only

slightly. During the puerperium no change in concentration vvas observed but a normalization occurred about 6 wPcks after parturition. However, the biologic functions of these inhibitors are not properly understood and the specific functions during pregnancy and in connection with parturition have not been demonstrated.'"

Blood coagulation and fibrinolysis m puerperium

3

As new methods have now been worked out to determine the plasminogen in plasma,5 the total antifibrinolytic activity in plasma, 39 and the spontaneous fibrinolytic activity of resuspended euglobulin on fibrin plates," 8 it is of interest to study the changes in these parameters during the puerperium. Different blood coagulation factors, number and adhesiveness of platelets, and the urokinase excretion in urine were also studied in order to further illustrate the changes in these parameters after delivery. Material and methods

Healthy pregnant women were selected at random from the Department of Obstetrics and Gynaecology (Head: Professor S. Brody), University of Goteborg. No complications during pregnancy, at delivery, or during the puerperium were observed in this group. The antifibrinolytic activity in plasma was determined according to Y gge, Berg, and Korsan-Bengtsen. 39 Dilutions from 1:25 to 1 : I 00 of citra ted plasma were tested in a one-stage lysis time system which contained plasminogen ( 5 casein units per milliliter), urokinase (about 4 Ploug units per milliliteT, fibrinogen (0.05 Gm. per cent), and thrombin. The activity is given in per cent of a standard plasma. Buffer. One part of Tris HC! buffer (O.lM, pH, 7.4) was mixed with four parts of physiologic saline. Collection of blood. Nine milliliters of blood was collected from the antecubital vein \vith silicone-treated coarse needles and vvas

allowed to flow freely into a lusteroid tube containing 1 ml. 3 per cent trisodium citrate. The tube was centrifuged at 1,700 relative centrifugal force for 30 minutes at +4° C. The plasn1a was then collected in lusteroid tubes and kept in an ice bath until used or immediately frozen to -20° C. Factor I (fibrinogen) was determined in accordance with Morrison's syneresis meiliod as modified by Blomback. 11 To prevent lysis of fibrinogen and fibrin during the analysis, lysine was added as described by Bergstrom, Blomback. and Kleen. 7

4

May I, 1969 Am. J. Obst. & Gynec.

Ygge

Factor II, VII, and X activities (P & P) were determined according to Owren and Aas. 26 Factor V (proaccelerin) was determined according to Aas. 1 Factor VIII (antihemophilic factor) was determined according to Hardisty and MacPherson.16 Plasminogen determination in plasma was made according to Berg, Korsan-Bengtsen, and Ygge. 5 Platelets were counted using Bjorkman's method. 10 Platelet adhesiveness in plasma was determined as described by Odegaard, Skalhegg, and Hellem. 40 Adenosine diphosphate at a final concentration of 0.1 f.Lg per milliliter was added to platelet-rich plasma. The difference in platelet count before and after passing the plasma through a standardized glass bead column gives the number of adhesive platelets which is expressed m per cent of the original platelet count. Spontaneous fibrinolytic activity in the euglobulin fraction of human plasma precipitated at pH 6.4 was determined using a modified fibrin plate method. 38 The plate contained purified plasminogen-free fibrinogen at a final concentration of 0.05 per cent, purified plasminogen-free thrombin, and agar at a final concentration of 1 per cent Urokinase, which is a plasminogen activa-

tor and normally appears in the urine, was determined principally as described for the determination of purified urokinase. 6 A 5 mi. portion of the urine was dialyzed against 1,000 mi. of buffered physiologic saline for 2 hours at room temperature. The urine was then diluted 1 : 2 and 1 :4 in plastic tubes with buffered physiologic saline. These dilutions were tested in the following lysis time system at 37° C.: 0.1 mi. plasminogen, 5 caseinolytic units per milliliter; 0.1 mi. thrombin, 50 NIH per milliliter; 0.1 mi. of the urine dilution to be tested; 0.1 mi. fibrinogen, 0.05 Gm. per cent. The lysis time was recorded. In the test system, the same purified fibrinogen, plasminogen, and thrombin preparations were used as described in the work on the determination of purified urokinase. 6 The activity of the urine dilutions was read from a standard graph made with purified urokinase 6 and a mean value of the two dilutions was calculated. The standard curve was checked with a freshly diswlved urokinase standard preparation every time during this study. The activity is expressed in Ploug units per milliliter of unne. Results

Table I shows the levels of the different parameters one to 4 weeks before delivery. A~ a comuarison. the levels of the same parameters in healthy nonpregnant women

-

--

--

~

.I

Table I. Levels of the different parameters 1-4 weeks before delivery compared with the levels in a group of nonpregnant '.vomen* Pregnant

No. of piateiets (x 10-3/mm.3) Platelet adhesiveness (%) Factor I (fibrinogen) (Gm. %) Factor II-VII-X (P&Pj (%) Factor V (%) Factor VIII (AHF) (%) Plasminogen (casein units/mi.) Spontaneous fibrinolytic activity (mm. 2 ) Antifibrinoiytic aciivity (%) Urokinase (Ploug units/mi. urine)

142 44 0.58 150 124 269 18.6 120 90 1.4

x ± S.D.

± 70 ± 8 ± 0.08 ± 14

( 8) ( 8) ( 10)

I Nonpregnant x ± S.D. I Significance ± 4i 162 ± 18 52 0.27 ± 0.05 94 ± 26 ± 39 122 108 ± 43 12.5 ± 2.5

± 18 ± 87

( tl) ( 8) ( 7)

± 2.4

(10)

± 16 ± 9

( 8)

118

7)

102

± 0.6

(

7)

6.8

*The figures within parentheses show the number of women analyzed.

(15)

(15) ( 15) (15)

( 15) ( 14) (15)

of difference

Not significant Not significant 0.001; t = 11.92 p

< < 0.001; t == 6.71 Not significant p < 0.001; t = 4.63 p < 0.001; t == 6.12 p

± 21 ± 24

(14)

Not significant

/1C)\

l\.T- .._

± 3.0

(20)

\l.:J)

nut

p

-~---!.c.

___ ...

~lguun.:;a.ut

< 0.001; t =

7.64

Volume 1114

Blood coagulation and fibrinolysis in puerpenum

Number I

%

0 I

I

I

I

1'1' ANTE PARTUS PARTUM

I WEEK

2 WEEKS

Fig. 1. Changes in the number of platelets.

%

1'1' ANTE PARTUS PARTUM

1' 1 \VEEK

Fig. 2. Changes in the fibrinogen concentration.

2 WEEKS

5

.\Ia~

6 Ygge

.\m.

%

100

50

1'1' ANTE

PARTUS

l WEEK

2 WEEKS

PAR TUM

Fig. 3. Changes in the prothrombin-pru(·"m en in test.

%

50

II ANTE PARTUS PARTUM

Fig, 4. Cl,anges in the Factor\' arti\iry.

1 WEEK

2 WEEKS

J.

I I YO~

()h,t.. & (:yare

Volume 104 Number 1

Blood coagulation and fibrinolysis in puerperium

%

It

1'

ANTE PARTUS WEEK PAR TUM Fig. 5. Changes in the Factor VIII activity.

2 WEEKS

%

1'1' ANTE PARTUS PARTUM

t 1 WEEK

Fig. 6. Changes in the plasminogen concentration.

t 2 WEEKS

7

8

~tal

Ygge

I I'IW

.\n1 ,I < >IJ'>L & Cyt1n·.

20 to 30 years old arc shown. In the pregnant women there was an increased level of Factor L Factor II, VII, and X activities measured with the P & P test, Factor VIIL :md of plasminogen. As pointed out in the introduction, these are well-known change' described previously by many authors. Table I also shows that the urokinase excretion in the urine is very low during the last period of pregnancy compared with the excretion in nonpregnant woman. Such a low urokinase excretion during pregnancy has not previously been described. In order to illustrate the dynamic changes during the puerperium in the above parameters. the antepartum levels of these paramPtcrs for each woman wen~ st't at I 00 pet cent. The changes aftPr delivery were then

I

150

('alculated as per cent of the antepanunt values. In the following figures each woman is represented by a separate line. Platelets. Fig. 1 shows that, in most cases, there was a decrease in the number during the first day' aftcr delivery, hut about n1w week post partnm there was an increase rompared with the values before delivery. Such changes in the number of platelets post partum are in agreement with the findings of other authorsY• ,r, The platelet adhesiyencss was also studied in these 8 rases. Great variations were found post partum hut not typical course could be observed. \•1highfl'1 has found increased platelet adhE·siveness following· parturition. Factor I. Tht>n~ was a rapid decrease i11 the librinm;en concentration post partunL

.

~ I I;:~.,

\ \

IIf\ \

j

..

~ VZ:~= lOOt~\~·~~-~:.. . . -~~

J

. .-------·

~ II ANTE PARTUS PAR TUM

Fig. 7. Changes in the spontaneous fibrinolytic activity.

1 WEEK

Volume 104

Blood coagulation and fibrinolysis in puerperium 9

Number 1

but a new increase occurred 5 to 8 days post partum (Fig. 2). This new increase in the fibrinogen concentration has been observed previously by others. 4 • 23 The fibrinogen concentration then normalized about two weeks after delivery. Factor II, VII, and X activities (P & P). Fig. 3 shows that there was a successive de·· crease in the activities measured by the P & P test. A normalization was reached one to 2 weeks after delivery. Factor V. As shown in Fig. 4, the Factor V activity increased after delivery in all cases compared with the prepartum values and normalized after about one week. This finding is in agreement with the finding of Davidmn and TomlinY

%

Factor VIII. Great vanat10ns in the activity were observed in some cases but most often normalization occurred a few days after delivery (Fig. 5) . Plasminogen. As was the case with the fibrinogen concentration post partum, there was a rapid decrease in the plasminogen concentration compared with prepartum values (Fig. 6). There was also a new increase before normalization about one week post partum. Spontaneous fibrinolytic activity. A rapid increase in this activity was observed during the first days after delivery. Then there was a return to prepartum values after about one week (Fig. 7). Antifibrinolytic activity. Fig. 8 shows that,

·~.

150

0

----· /'

·~

~------·

"'·

50

it ANTE PARTUS PARTUM

t 1 WEEK

Fig. 8. Changes in the antifibrinolytic activity of plasma.

2 WEEKS

10 Ygge

\m.

J.

:\!av 1. 1!l69 Ob-.L & !;vJ.ec

% 1000

I 500

--·

·-

1'1' ANTE PARTUS PARTUM

I

1 WEEK

2 WEEKS

Fig. 9. Changes in the mokinas(' rxcrction in urine.

in most cases, there was an increased antifibrinolytic activity after delivery compared with the prepartum values. In most cases, the prepartum values were not reached after 2 weeks. Urokinase. Because of difficulties in urin<: collection, the excretion of urokinase in the morning urine was followed only for 2 to 3 days in some cases. As is shown in Table I. the excretion was low befort> delivery. Fig. C) shows that there was ~~ very pronounced increase after delivery and normal levels were reached after about one ;veek. Comment

It is reasonable to assume that the changes observed in blood dotting and fibrinolysis

during pregnancy and the puerperium arc of the followin,g physiologic significance. The increased level of dotting factors normally seen during pregnancy is of importance to obtain a rapid and effective hemostasis after parturition. If the lew! of these factors were normal at the start of delivery. tlw con~umption of the clotting factors in mnnection with delivery may lead to dang;erously low l('Vt~ls, and an appropriate hemostasis could not be obtained. On the other hand. the sudden and extensi,·e activation of ttw clotting systern in combination with a t'ertain degn•e of immobility of the patient after delivery would increase the risk of thrombosis. Tlw activation of the fibrinolytic sv~­ tettt during· this period can be seen as ,111 at-

Volume 104 Number 1

tempt from the body to meet with this danger. A decreased level of fibrinogen, Factor VIII, and plasminogen of the magnitude seen after delivery is not observed in connection with ordinary surgery. 37 However, after very extensive surgical procedures, a decrease in these factors of such a magnitude occurs. 37 Thus, the changes observed in the hemostatic mechanism in connection with delivery can be compared to the changes seen after an extensive operation, except that the pregnant woman starts with a higher concentration of some blood clotting factors and of the precursor of the fibrinolytic enzyme. Later during the puerperium there is an increase in the number of platelets and in the concentration of fibrinogen, plasminogen, and, in some cases, of Factor VIII before normal values are reached about 2 weeks post partum. This secondary increase corresponds to the rebound phenomena which are seen after major surgery. 37 The higher spontaneous fibrinolytic activity observed during the puerperium compared with the activity during the postoperative period 37 may be due to the higher plasminogen level at the start of delivery. The physiologic significance of the low urokinase excretion in the urine during pregnancy and its rapid normalization after delivery, as shown in this work, is not known. Urokinase is an activator of plasminogen and normally appears in the urine. Urokinase is probably produced by the kidney 31; but may be of some importance as an activator of the fibrinolytic system in the bloodP It is of importance to know the normal changes in blood coagulation and fibrinolysis during pregnancy-especially the dynamic changes in these systems after delivery. Such

Blood coagulation and fibrinolysis in puerperium

11

knowledge is necessary to be able to interpret the changes observed in the hemostatic mechanism in hemorrhagic or thromboembolic complications in connection with delivery. As pointed out earlier, there are normally changes in the hemostatic mechanism which reflect an activation of the coagulation and fibrinolytic system. In the hemorrhagic diathesis which complicates pregnancy, for instance, due to abruptio placentae, a defibrinating syndrome is produced with a marked decrease in Factors I, V, and VIII, in plasminogen, and in the number of platelets. R As shown in this vvork, such changes are also observed during the first days after normal delivery but at a lower level. An important difference is that normally the Factor V activity is increased post partum. As for the etiology of the thromboembolic complications sometimes found during the puerperium, the normal changes in the hemostatic mechanism during this period may be one of the factors which predispose to thrombosis. Normally, there is wpposed to be an equilibrium of the factors mvolved in enhancing and preventing clotting of the blood in order to maintain its fluidity. During the course of pregnancy some factors are increased slowly in concentration and activity and a new equilibristatic balance is rapidly changed by trauma, such as delivery, and if other factors are present which predispose to thrombosis, for instance, injured vessel walls or regions of reduced blood flow, intravascular clotting may occur. If this argumentation is correct, it can explain why the incidence of thromboembolic complications is greater during· the puerperium than during pregnancy and why the incidence is especiaiiy high in women with varicose veins. 17 • 30

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