Question 9.3

With respect to the coagulation status of a third trimester pregnant patient compared to that in the nonpregnant state, indicate the change you would anticipate for each test listed below:

Platelet count

Factor V, Vll, 'X, X levels

Fibrinogen level

Protein S level

(20% marks)

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College answer

a) Platelet count: Decrease

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

c) Fibrinogen level: Increase

d) Protein S level: Decrease


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


Bremme, Katarina A. "Haemostatic changes in pregnancy." Best practice & research Clinical haematology 16.2 (2003): 153-168.

Moore, Lisa E., and Nigel Pereira. "Physiological changes of pregnancy." Maternal Critical Care: A Multidisciplinary Approach 107 (2013).

Katz, D., and Y. Beilin. "Disorders of coagulation in pregnancy." BJA: British Journal of Anaesthesia 115.suppl_2 (2015): ii75-ii88.