Coagulation

Continuing low-grade coagulopathy is a feature of normal pregnancy [10]. Several of the potent procoagulatory factors rise from at least the end of the first trimester (Fig. 2.5). For example, Factors VII, VIII and X all rise and absolute plasma fibrinogen doubles, while antithrom-bin III, an inhibitor of coagulation, falls. The erythrocyte sedimentation rate rises early in pregnancy due to the increase in fibrinogen and other physiological changes. Protein C, which inactivates Factors V and VIII, is probably unchanged in pregnancy, but concentrations of Protein S, one of its co-factors, fall during the first two trimesters. An estimated 5-10% of the total circulating fibrinogen is consumed during placental separation, and thromboem-bolism is the main cause of maternal death in the UK. Plasma fibrinolytic activity is decreased during pregnancy and labour, but returns to non-pregnant values within an hour of delivery of the placenta, suggesting strongly that the control of fibrinolysis during pregnancy is significantly affected by placentally derived mediators. Table 2.4 summarizes changes in some coagulation and fibrinolytic variables during pregnancy.

INTRINSIC PATHWAY XII

"I

VIII

VIIIa IXa Phospholipid

VIIa

EXTRINSIC PATHWAY

Tissue thromboplastin j

Phospholipid j

II -IIa (thrombin)

Fibrinogen-Fibrin monomer

Fibrin polymer

XIII

XIIIa

FIBRIN

Fig. 2.5 Alterations in the coagulation pathways associated with human pregnancy. Factors which increase during normal pregnancy are printed in bold type.

Table 2.4 Percentage changes in some coagulation (upper) and fibrinolytic variables and fibronectin levels are expressed from postpartum data in the same women

First

Second

Third

trimester

trimester

trimester

PAI-1 (mg/ml)

-10

+68

+183

PAI-2 (mg/ml)

+732

+1804

+6554

t-PA (mg/ml)

-24

-19

+633

Protein C (% activity)

-12

+10

+9

AT III (% activity)

-21

-14

-10

TAT III

+362

+638

+785

Fibronection (mg/l)

+3

-12

+53

PAI-1 and PAI-2, plasminogen activator inhibitors 1 and 2; t-PA, tissue plasminogen activator antigen; AT III, antithrombin III; TAT III, thrombin-antithrombin III complex.

The mean values shown are those at the end of each trimester, and are thus not necessarily the maxima. Note the very large rises in PAI-2 (placental type PAI) and TAIIII complexes in the first trimester. (Data from Halligan ef al. 1994)

PAI-1 and PAI-2, plasminogen activator inhibitors 1 and 2; t-PA, tissue plasminogen activator antigen; AT III, antithrombin III; TAT III, thrombin-antithrombin III complex.

The mean values shown are those at the end of each trimester, and are thus not necessarily the maxima. Note the very large rises in PAI-2 (placental type PAI) and TAIIII complexes in the first trimester. (Data from Halligan ef al. 1994)

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Pregnancy Diet Plan

Pregnancy Diet Plan

The first trimester is very important for the mother and the baby. For most women it is common to find out about their pregnancy after they have missed their menstrual cycle. Since, not all women note their menstrual cycle and dates of intercourse, it may cause slight confusion about the exact date of conception. That is why most women find out that they are pregnant only after one month of pregnancy.

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