Question 9.3

College answer

a) Platelet count: Decrease

b) Factors V, VII, IX, X level: Increase

c) Fibrinogen level: Increase

d) Protein S level: Decrease

Discussion

The overall trend in pregnancy is towards hypercoagulability. In the third trimester, coagulation activity is about double that of normal. The best source to read further is probably the 2003 article by Katarina Bremme.

In brief:

• Platelet count decreases, particularly in late pregnancy
  • Normal pregnancy is associated with a degree of enhanced platelet destruction which is compensated for by increased production
  • The destruction takes place in the uteroplacental circulation
• Factors VII, VIII, IX, X, XII and von Willebrand factor increase significantly; Factor VII may increase as much as tenfold.
• Factor XI decreases down to 60–70% of the non-pregnant value
• Factors II and V do not change in pregnancy
• Fibrinogen levels increase throughout pregnancy
• Protein S levels decrease progressively during pregnancy
• Protein C activity is unaffected by pregnancy
• Plasma fibrinolytic activity decreases throughout pregnancy, but returns to normal within one hour of delivery. This is due to synthesis of plasminogen activator inhibitor-1 and -2 by the placenta