PROS1 and hyperhomocysteinemia: Biological risk factors include protein C, protein S, and antithrombin III deficiencies; Factor II or Factor V mutations; hyperhomocysteinemia linked to a homozygous mutation in the MTHFR gene; homozygous sickle cell disease; anticardiolipin antibodies; and circulating lupus anticoagulant in the mother's blood which is transmitted to the fetus in utero [4–6].