PROS1 and hereditary antithrombin deficiency: The Society of Obstetric Medicine of Australia and New Zealand [13] has classified inherited thrombophilia types as significant (antithrombin deficiency, factor V Leiden homozygous mutation, combined heterozygous mutation of factor V Leiden and prothrombin, protein S deficiency, protein C deficiency) and weak (factor V Leiden heterozygous mutation, prothrombin heterozygous mutation).