Why Coagulopathy Occurs in Amniotic Fluid Embolism
Coagulopathy in amniotic fluid embolism results from disseminated intravascular coagulation (DIC) triggered by amniotic fluid activating Factor VII and platelets, combined with a profound inflammatory response that further activates the clotting cascade, often accompanied by hyperfibrinolysis. 1
Primary Mechanisms
Tissue Factor Activation and DIC
- Amniotic fluid directly activates Factor VII and platelets upon entering maternal circulation, initiating widespread intravascular coagulation. 1
- The inflammatory response triggered by amniotic fluid components further amplifies clotting cascade activation, creating a consumptive coagulopathy. 1
- Elevated tissue factor levels are characteristic of amniotic fluid embolism-related DIC, distinguishing it from other obstetric coagulopathies. 1
Hyperfibrinolysis Component
- Both plasminogen activators and plasminogen activator inhibitors have been identified in amniotic fluid, contributing to hyperfibrinolysis as a major component of the coagulopathy. 1
- Disproportionately low fibrinogen levels and exorbitantly elevated D-dimers occur early, often before significant consumption of platelets or antithrombin. 2
- The hemoglobin/fibrinogen ratio increases early as fibrinogen drops faster than hemoglobin, serving as a clinical marker for consumptive coagulopathy before overt hemorrhage. 3
Temporal Pattern
Variable Onset
- DIC may manifest immediately following cardiovascular collapse or develop in later phases of the syndrome. 1
- In rare cases, isolated coagulopathy may be the only presenting finding without cardiorespiratory compromise, though this carries high mortality. 1, 4
- The coagulopathy typically follows the initial cardiopulmonary phase but can occasionally precede hemodynamic instability. 4
Clinical Manifestations
Hemorrhagic Complications
- DIC presents with bleeding from venipuncture sites, surgical incisions, hematuria, gastrointestinal hemorrhage, and profuse vaginal bleeding. 1
- Uterine atony commonly coexists due to diminished uterine perfusion from the cardiovascular collapse. 1
- Diffuse intravascular clotting from DIC contributes to ischemic distal organ dysfunction and multiorgan failure through microvascular thrombosis. 1
Important Clinical Pitfall
Do not diagnose amniotic fluid embolism based solely on hemorrhage from persistent uterine atony with secondary coagulopathy—this represents a common diagnostic error. 1 True amniotic fluid embolism requires the classic triad of hypotension, hypoxia, and subsequent coagulopathy, not isolated bleeding with dilutional or hypovolemic coagulopathy. 1