6A.1 Fibrin formation disorders and pregnancy loss

Abstract

Fibrinogen, the soluble clottable protein in the blood, is converted into fibrin by the proteolytic action of thrombin. The insoluble polymerized fibrin then becomes cross-linked by activated factor XIII resulting in mechanically stabilized fibrin protected from fibrinolysis. Severe deficiency of fibrinogen and factor XIII are associated with severe bleeding diathesis and with pregnancy loss. Both factor XIII and fibrinogen play an essential role in placental implantation and maintenance of pregnancy. Investigation of pregnancy loss in fibrinogen and factor XIII knock-out mice demonstrated that miscarriages are due to the improper anchoring of cytotrophoblasts after their invasion of the endometrium and to the uncontrolled hemorrhage along the planes of placental-decidual attachment. It is also clear that maternal fibrinogen and factor XIII are required to maintain pregnancy, and factor XIII present in the plasma and not in the cells is essential. Supplementation therapy with factor concentrates is advocated throughout pregnancy.