The diagnosis of thrombophilia is complex, including the biological elements and genetic elements that predict IUGR (factor V Leiden mutation, MTHFR C667T mutation, protein S deficiency, antithrombin deficiency, factor VII polymorphism, antiphospholipid antibodies), while other types of diagnosis are still under debate and require more data (protein C, PAI-1, certain combinations of mutations) and validation using larger randomized control trials. The gene discussed is PROS1; the disease is thrombophilia.