Haemostasis in normal pregnancy: a balancing act?

Area of Science:

• Obstetrics and Gynecology
• Hematology
• Physiology

Background:

• Pregnancy significantly elevates the risk of venous thrombosis, with venous thromboembolism incidence being six times higher than in non-pregnant women.
• Despite increased procoagulant markers during pregnancy, the overall incidence of venous thromboembolism remains low.
• The hemostatic system undergoes substantial, procoagulant-leaning changes in preparation for the delivery's hemostatic challenges.

Purpose of the Study:

• To investigate the complex physiological adaptations in the hemostatic system during normal pregnancy.
• To understand how the balance between coagulation and fibrinolysis is maintained despite procoagulant changes.
• To identify factors that counterbalance procoagulant shifts to prevent excessive thrombosis.

Main Methods:

• Review of physiological changes in coagulation and fibrinolysis markers during pregnancy.
• Analysis of the balance between procoagulant and anticoagulant factors.
• Examination of fibrinolytic activity and specific factor levels (e.g., factor XI, monocyte tissue factor).

Main Results:

• Normal pregnancy involves significant alterations in hemostasis, generally favoring coagulation.
• A delicate balance is maintained through complex physiological changes, including increased fibrinolytic activity.
• Decreased levels of factors like factor XI and reduced monocyte tissue factor expression contribute to counterbalancing procoagulant tendencies.

Conclusions:

• The hemostatic system in pregnancy adapts to ensure vascular integrity during delivery.
• Pregnancy maintains a dynamic coagulation/fibrinolysis balance, crucial for preventing both hemorrhage and thrombosis.
• Specific inhibitory mechanisms actively counteract procoagulant changes, contributing to the low incidence of venous thromboembolism in healthy pregnancies.