Swedish obstetric thromboprophylaxis guideline: background and update

Figures & data

Table 1. Risk points for venous thromboembolism (VTE), compiled to total risk score as basis for prescribing thromboprophylaxis.

Risk points	1p	2p	3p	> 4p^a
				High risk
Risk factors
	Heter FV Leiden mut	Prot S deficiency	Hom FV Leiden mut	Prior VTE
	Heter prothrombin mut	Prot C deficiency	Hom prothrombin mut	APS without prior VTE
	Age > 40 years	Immobilisation^b	Double mutation	OHSS^c
	BMI^d 30–40	BMI^d > 40
	Heredity for VTE^e
	Inflammatory bowel disease
	Hyperhomocysteinaemia^f		Very high risk^g
	Other major risk factor^h		Chronic anticoagulation^i
	Postpartum risk factors		Antithrombin deficiency
	Preeclampsia		Repeated VTEs
	Placental abruption		APS with VTE
	Caesarean section		Covid-19 pneumonia, required oxygen
	Blood transfusion
	Stillbirth
	Severe infection, sepsis

Heter: heterozygous; Hom: homozygous; mut: mutation; APS: anti-phospholipid syndrome; Prot: protein, FV: Factor V; DOAC: direct oral anticoagulants; ASA: acetylsalicylic acid

^a Prior VTE or APS without VTE yields risk score 4.

^b Fracture cast, strict bed rest or Covid 19 infection, short-term thromboprophylaxis.

^c OHSS, thromboprophylaxis during whole first trimester.

^d BMI early pregnancy.

^e VTE among 1st-grade relative aged < 50 years.

^f Homocysteine >8 µmol/L during pregnancy, risk of sinus thrombosis.

^g Women in this group are classified as very high risk, independent of other risk factors.

^h For example cancer, cancer treatment, SLE, heart disease, sickle cell trait or essential thrombocytosis.

ⁱ Warfarin, DOAC, LMWH, but not low-dose ASA.

Table 2. Management, based on risk score in Table 1.

Risk score = 1	No treatment. Lifestyle advice
Risk score = 2	Postpartum normal-dose prophylaxis at least 7 days and short-term, normal-dose prophylaxis during temporary risk factor
Risk score = 3	Postpartum normal-dose profylax for at least 6 weeks
Risk score > 4	Antepartum normal-dose prophylaxis beginning as soon as pregnancy is known, and until at least 6 weeks postpartum

Moderate- or high-dose prophylaxis.

Table 3. Dosage, low-molecular-weight heparin (LMWH).

	Weight^a (kg)	Dalteparin s.c. IE/24 h	Tinzaparin s.c. IE/24 h	Enoxaparin s.c. mg/24 h
Risk score = 2–4
Moderate to high risk	< 90	5,000	4,500	40
‘Normal-dose prophylaxis’	> 90	7,500^b	8,000^b	60^b
‘Very high risk’ of VTE^c
‘High-dose prophylaxis’ (twice daily)	<50	2,500 × 2^b	2,500 × 2^b	20 × 2^b
	50–90	5,000 × 2^b	4,500 × 2^b	40 × 2^b
	>90	7,500 × 2^b	4,500 + 8,000^b	60 × 2^b

^a Weight in early pregnancy.

^b Initial dose.

^c measurable anti-FXa activity before next dose, i.e. >0.05–0.1 IE/mL.

VTE, venous thromboembolism.

Table 4. Absolute risk of venous thromboembolism at different risk scores.

VTE risk score	Risk increase	Prevalence		Pregnancy, absolute risk	Postpartum, absolute risk
				VTE/10,000	VTE/10,000
		AP	PP
0p	1	73%	66%	≈1.2	≈0.9
1p	5	17%	24%	≈6	≈5
2p	25	2.6%	6.1%	≈30	≈23
3p	125	0.2%	0.9%	≈160	≈120
4p, ‘High risk’	≈500	0.4%	0.4%	≈500	≈500
‘Very high risk’	> 750	<0.1%		> 750	> 700

AP: antepartum; PP: postpartum; p: points;

VTE : venous thromboembolism.

Data availability statement

Data sharing not applicable – no new data generated