Pregnancy: Hematologic changes

Plasma volume increases 45% at term, RBC volume increases 20%, thus while pregnant patients have increased RBC mass, they appear anemic. Normal hemoglobin is 12 g/dl. During labor, contractions squeeze blood into the systemic circulation, and after delivery, uterine involution autotransfuses 500 cc/blood. Note that clotting factors (I, VII, VIII, IX, X, XII) are elevated, protein S (anticoagulant) is decreased, and there is acquired resistance to protein C. Pregnancy is thus a hypercoagulable state. ALSO NOTE THAT both platelet generation and destruction increase, with variable effects. Importantly, 7.6% of term parturients have platelets < 150,000, AND 1% have < 100,000 platelets at term.