What do systematic reviews say?

Low molecular weight heparin vs placebo or no prophylaxis

Low molecular weight heparin showed no clear difference in pulmonary embolism compared with no prophylaxis or placebo (low certainty).

• Low molecular weight heparin for prevention of venous thromboembolism in patients with lower‐limb immobilization 2017 · Cochrane Headline outcomes only
  OR 0.5 [0.17, 1.47]
  5 studies · 2517 participants
  Low

Low molecular weight heparin vs placebo or no prophylaxis

• Low molecular weight heparin for prevention of venous thromboembolism in patients with lower‐limb immobilization 2017 · Cochrane Headline outcomes only
  no estimate extracted
  8 studies · 3111 participants
  GRADE not reported

Low‐molecular‐weight heparins or heparinoids vs unfractionated heparin

Low‐molecular‐weight heparins or heparinoids showed no clear difference in pulmonary embolism during treatment period (range 6 days to 16 days) compared with unfractionated heparin (low certainty).

• Low‐molecular‐weight heparins or heparinoids versus standard unfractionated heparin for acute ischaemic stroke 2017 · Cochrane Headline outcomes only
  OR 0.57 [0.23, 1.41]
  6 studies · 1250 participants
  Low

Low molecular weight heparin vs vitamin K antagonist (VKA)

Low‐molecular‐weight heparin (LMWH) showed no clear difference in pulmonary embolism (up to 3 months) compared with vitamin K antagonist (VKA) (low certainty).

• Anticoagulation for people with cancer and central venous catheters 2018 · Cochrane Headline outcomes only
  RR 1.7 [0.74, 3.92]
  2 studies · 327 participants
  Low