Table 2. Lyon VTE risk score system by Dargaud et al.

Risk factor	Venous thromboembolism	Score
Personal history of VTE	History of VTE related to pregnancy (occurred during the antepartum period), or cerebral vein thrombosis or massive PE/VTE in childhood	6
	Spontaneous or estrogen induced PE or proximal DVT	3
	Transient risk factor induced PE or proximal DVT	2
	Spontaneous or estrogen induced distal calf DVT	2
	Transient risk factor induced distal calf DVT	1
If there is a personal history of VTE	Recurrent VTE history	3
	Residual venous thrombi with clinical signs of post thrombotic syndrome	3
	Recent VTE history <2 years	2
Thrombophilia	Homozygous mutations, combined thrombophilia risk factors, protein C	1
	Deficiency, protein S deficiency, heterozygous F5 G1691A mutation
	Heterozygous F2 G20210A mutation
	No thrombophilia detected but family history of severe recurrent VTE
Other risk factors	Bed rest, immobilization	2
	Twin pregnancy	1
	Age >35	1
	BMI >30	1

They propose the following depending on the score: <3 no antenatal prophylaxis; 3–5 LMWH starting on the third trimester; ≥6 LMWH starting during the first trimester. VTE, venous thromboembolism; DVT, deep venous thrombosis; LMWH, low molecular weight heparin.