Thromboembolic prophylaxis with low molecular weight heparin during pregnancy

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Abstract
The objective of this study was to show that low molecular weight heparin (LMWH) can be used in preventing veno-pulmonary thromboembolic diseases in pregnancy. Twenty-four women carrying 27 pregnancies with known risk of veno-pulmonary thromboembolic diseases in pregnancy were prophylactically treated with LMWH (dalteparin) during part of their pregnancy. Our therapeutic target was a plasma concentration of 0.20-0.50 anti-Xa U/ml measured 2-6 h after subcutaneous administration of LMWH into the abdominal wall. To obtain this anti-Xa activity the patients were given total doses of 2500-10,000 anti-Xa U daily. Monitoring of anti-Xa activity in patients receiving < or = 5000 U/day was not necessary. Twelve out of the 24 women received LMWH at the time of delivery. Our biochemical assay could not show the presence of anti-Xa activity in the blood samples from the babies although it was possible to show anti-Xa activity in their mothers. In three out of 24 women, blood samples showed activation of coagulation. These patients were changed to the vitamin K antagonist phenindione. None of the treated women showed any clinical or paraclinical signs of thromboembolic diseases during pregnancy or 6 weeks postpartum. All the babies were born healthy. None of the women had any side effects due to the treatment.