Table 1.

Hematologic Changes During Normal Pregnancy

Blood Clotting Factor	Pregnancy-Associated Changes
Protein C	No change
Protein S	Decreased by ≈50% compared to prepregnancy values
Antithrombin III	Decreased by ≈20% compared to prepregnancy values
Plasminogen activator 1	Increased
Plasminogen activator 2	Increased
Prothrombin time	No change
Activated partial thromboplastin time	No change
Platelets	Decreased by ≈20% compared to prepregnancy values
Von Willebrand factor	Increased by >100% compared to prepregnancy values
Fibrinogen	Increased by >100% compared to prepregnancy values
Prothrombin	Increased
Tissue thromboplastin	Increased
Factor IV	No change
Factor V	No change
Factor VII	Increased by >1000% compared to prepregnancy values
Factor VIII	Increased by >100% compared to prepregnancy values
Factor IX	Increased by >100% compared to prepregnancy values
Factor X	Increased by >100% compared to prepregnancy values
Factor XI	Values vary during pregnancy (can increase or decrease)
Factor XII	Increased by >100% compared to prepregnancy values
Factor XIII	Decreased by ≈50% compared to prepregnancy values