Our patient also gave a history of three first trimester spontaneous abortions; thus a full laboratory investigation for thrombophilias was performed, including factor V Leiden gene mutation, prothrombin gene mutation, protein-C and protein-S activity, MTHFR gene mutation, hyperhomocysteinemia, systemic lupus erythematosus, and antiphospholipid syndrome. Here, PROS1 is linked to antiphospholipid syndrome.