A very soluble protein found in the blood that forms the progressively less soluble protein fibrin when blood clots, through the action, first of thrombin and then of factor XIII.

A complex set of blood and tissue components capable of a cascade of events causing blood to clot. The central event is the conversion of soluble fibrinogen to insoluble, polymerised fibrin through the action of thrombin. In a more moderate way, the coagulation system (and these molecules) lay down the scaffolding for normal development of the placenta, so that abnormalities of blood coagulation may contribute to recurrent miscarriages.

A polymer that is formed from the circulating protein fibrinogen when blood clots (see coagulation system). Also important in the formation of the placenta, so abnormalities of fibrinogen can cause recurrent miscarriage.