Up to 83% of patients develop some form of DIC with or without
clinically significant bleeding. Amniotic fluid contains activated
coagulation factors II, VII, and X. It also has a direct factor X activating
property, induces platelet aggregation, releases platelet
factor III, and has a thromboplastin-like effect. Lockwood and colleagues
suggested that amniotic fluid contains a tissue factor,
which is a procoagulant.5 The source of procoagulant is sloughed
fetal skin and respiratory, gastrointestinal, and genitourinary
epithelia. Tissue factor is responsible for activating the extrinsic
pathway by binding with factor VII. This complex in turn triggers
clotting by activating factor X. Once clotting is triggered within
pulmonary vasculature, local thrombin generation can then cause
vasoconstriction and microvascular thrombosis and release of vascular
endothelin. Endothelin depresses myometrial and myocardial
contractility. The end results include massive haemorrhage and
haemodynamic collapse.