Dose Adjustment Of Low Molecular Weight Heparins (LMWH) Improves Pregnancy Outcome In Thrombophilic Women

Acquired and inherited thrombophilias are associated with unfavourable pregnancy outcome. Low-molecular-weight heparin (LMWH) has demonstrated utility in the prevention and treatment of thrombosis during the pregnancy. There is no consensus on the dose of LMWH for prophylaxis, between fixed dose and “adjusted” dose according to anti-Xa levels.

We report our experience the management of heparin-therapy during pregnancy in thrombophilic women.

We performed a retrospective analysis of patients with high risk of venous thromboembolism (VTE) and obstetric complications during pregnancy. Table 1 shows the risk factors of VTE in pregnancy. The obstetric complications considered were: preeclampsia, fetal growth restriction, fetal death and recurrent miscarriages. All patients were prescribed enoxaparin 70-100 IU /Kg SC once daily. To determine the dose of LMWH we evaluated levels of anti-factor Xa (chromogenic test) and the utero-placental circulation with color Doppler ultrasound. Dose adjustment was performed if the activity of factor Xa was suboptimal (prophylaxis range > 0.4IU/ml and < 0.8 IU/ml anti-Xa value) or were detected alteration in the utero-placental circulation.

Time of delivery, birth weights and Apgar-index.

70 pregnancies for 68 women were recruited between January 2008 and December 2012. The median age of patients was 35 years (range 25- 43years) and 7 (10%) were over 40. Twenty-four patients had a previous VTE and thirty-six had an obstetric complications.

No one patients reported thrombotic and/or hemorrhagic complications during heparin treatment. In 97 % of cases the time of delivery occurred after 36^th weeks of pregnancy, with a birth weight greater than 2600 grams and Apgar score index higher than 7.

The dose of LMWH had to be adjusted at least once during the course of the pregnancy and the mean daily dose was increased from 4.000UI to 8.000UI between the 12^th and 32^th week of gestation.

In pregnancy LMWH thromboprophylaxis enables the modulation of systemic haemostatic parameters by the inhibition of factor Xa and by increasing TFPI levels. In the literature-in some high risk pregnancy- the weight-based dosing of LMWH could seem to fail achieving a prophylactic anticoagulation.

In our experience adjusted doses prevent unfavourable events and improve fetal growth.

°Carriage of defects of antithrombin, protein C or S, factor V Leiden, G20210A prothrombin mutation, antiphospholipid syndrom

No relevant conflicts of interest to declare.