THROMBOPROPHYLAXIS IN PREGNANCY – Appendix 4

Thrombophilia screening for women planning a pregnancy/presenting in pregnancy

• If the woman has already had appropriate thrombophilia screening then repeat testing is not required.
• Thrombophilia testing is likely not suitable if the woman is receiving anticoagulants

For the woman with a previous venous thromboembolism (VTE)

1. If a woman has had a provoked VTE, it is not necessary to do a thrombophilia screen unless she has a strong family history of unprovoked VTE, in which case screen for antithrombin 3 deficiency​ (AT3).

She would have to have a strong family history of unprovoked VTE to undertake any thrombophilia screening as outside the context of pregnancy, a thrombophilia screen is only indicated for a person sustaining a VTE with 2 or more of the following criteria:

• age <45
• unprovoked VTE
• 2 or more family members with VTE (‘preferably’ unprovoked)

So a strong family history of unprovoked VTE would be such as an immediate relative with an unprovoked VTE that occurred under the age of 45 years, or such as an immediate relative with an unprovoked VTE along with another family member who had also sustained a VTE.

2. If a woman has had an unprovoked VTE – screen for AT3 deficiency. If the woman is not currently pregnant, also screen for antiphospholipid antibodies and Lupus anticoagulant

For the woman without a previous VTE

1. If a woman has a first degree relative with a history of provoked VTE – no thrombophilia screen is required.
2. If a woman has a first degree relative (under 45) with a history of unprovoked or estrogen related VTE –  perform a full inherited thrombophilia screen.

‘Low risk thrombophilia’ such as Heterozygous Factor V Leiden or prothrombin gene mutations will score 1 on the pregnancy VTE risk assessment.

‘High risk thrombophilia’ such as Protein S, C or antithrombin 3 deficiencies will score 3.

As there is an automatic score of 1 for the family history of unprovoked or estrogen related VTE , then finding a Protein S, C or antithrombin 3 deficiency in this circumstance will immediately produce a score of 4 with a requirement for thromboprophylaxis throughout the whole of pregnancy and the puerperium.

Notes:

Unprovoked VTE is where there has been NO clear initiating event such as an operation, trauma to legs/ trauma to veins from IV injecting or estrogen related (pregnancy, the contraceptive pill).  VTE’s in relation to travel however are deemed Unprovoked.

Thrombophilia screens are best done outwith pregnancy as Protein S and antithrombin 3 levels may fall and Protein C may rise in pregnancy BUT if above criteria met should still be undertaken.

Antiphospholipid antibody or Lupus anticoagulant screens are not required for an inherited thrombophilia screen.

If thrombophilia screening is indicated due to a family history then this will NOT be required IF it is clearly known that the affected family member had had appropriate thrombophilia screening and those results are normal.