Of all the coagulation factor deficiencies, only deficiency of factor XIII (FXIII) and fibrinogen are associated with pregnancy loss. FXIII deficiency and a complete or partial deficiency of fibrinogen are associated with bleeding since childhood, impaired wound repair, and recurrent spontaneous abortions. Both FXIII and fibrinogen play an essential role in placental implantation and maintenance of pregnancy. The causes of miscarriages in FXIII or fibrinogen-deficient women is discussed and an appropriate treatment advocated.