Recruitment Complete



low-molecular-weight HeparIn to prevent recurrent vte in preGnancy: a randomized controLled trial Of tWo doses


Principal Investigator – Dr. Fionnuala Ni Ainle

The HIGHLOW trial assesses the efficacy and safety of heparin treatment in pregnant women who have previously had a form of thrombosis, such as deep vein thrombosis or a pulmonary embolism (VTE, venous thromboembolism). Women who have had a VTE in the past have a higher risk of reccurence. Heparin is an anticoagulant (“blood thinner”) which has been proven to decrease the chance of a new VTE. The most common form is a low-molecular-weight heparin (LMWH).

In most hospitals LMWH is used during the pregnancy and in the 6 weeks following delivery as a precaution for pregnant women who have a history of VTE. There has not yet been sufficient research on the most effective and at the same time safe dosage. This is the reason that the dosage of LMWH differs in different hospitals. In this trial we want to compare the effect of an often used low dosage to a higher dosage of LMWH. We want to test if the higher dosage decreases the risk of a VTE even more, without the treatment becoming less safe (ie with more bleeding).

In this trial we use the LMWH Tinzaparin. Tinzaparin is a drug which has already been used for many years in the prevention or treatment of VTE, also in pregnant women. It is given once daily via a subcutaneous injection.

Approximately 850 to 1100 patients will be taking part in this trial, receiving various different types of LMWH.

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