Testing for protein C, protein S, and antithrombin deficiency is generally indicated 2 to 4 weeks after completion of anticoagulation. There is a very limited value of test- ing in the acute setting or in patients taking warfarin (Class IIa; Level of Evidence B). 4. In patients with provoked CVT (associated with a transient risk factor), vitamin K antagonists may be continued for 3 to 6 months, with a target interna- tional normalized ratio of 2.0 to 3.0 (Class IIb; Level of Evidence C). 5. In patients with unprovoked CVT, vitamin K antago- nists may be continued for 6 to 12 months, with a tar- get international normalized ratio of 2.0 to 3.0 (Class IIb; Level of Evidence C). 6. For patients with recurrent CVT, VTE after CVT, or first CVT with severe thrombophilia (ie, homo- zygous prothrombin G20210A; homozygous factor V Leiden; deficiencies of protein C, protein S, or antithrombin; combined thrombophilia defects; or antiphospholipid syndrome), indefinite anticoagula- tion may be considered, with a target international normalized ratio of 2.0 to 3.0 (Class IIb; Level of Evidence C). 7. For women with CVT during pregnancy, LMWH in full anticoagulant doses should be continued through- out pregnancy, and LMWH or vitamin K antagonist with a target international normalized ratio of 2.0 to 3.0 should be continued for 6 weeks post par- tum (for a total minimum duration of therapy of 6 months) (Class I; Level of Evidence C). 8. It is reasonable to advise women with a history of CVT that future pregnancy is not contraindicated. Further investigations regarding the underlying cause and a formal consultation with a hematologist or maternal fetal medicine specialist are reasonable (Class IIa; Level of Evidence B). 9. 