Objective: To assess the safety and efficacy of low-molecular-weight heparin (LMWH) in pregnancy and puerperium in women with previous acute iliofemoral deep venous thrombosis (DVT) treated with catheter-directed thrombolysis (CDT).
Materials and methods: Consecutive patients treated for acute iliofemoral DVT using CDT between June 1999 and June 2009 were followed yearly by colour duplex ultrasound scanning. A subgroup of these patients who became pregnant during the follow-up period, three months to 10 years after CDT, was included in the present study. During pregnancy, thromboprophylaxis using LMWH was prescribed according to individual risk assessment, and the women were regularly assessed for adverse events. Women on warfarin had this treatment discontinued before the sixth week of pregnancy in order to prevent potential teratogenic adverse effects. Administration of LMWH was started at international normalized ratio ≤ 2.0, and continued during pregnancy, delivery and puerperium. Postnatal, the anticoagulation treatment was converted back to warfarin and LMWH discontinued after a bridging period. Women, who, prior to pregnancy, had discontinued anticoagulation treatment after CDT, were prescribed anticoagulation treatment using LMWH as early in pregnancy as practical. LMWH was continued during pregnancy, delivery and for six weeks postpartum. All women were prescribed graduated compression stockings.
Results: A total of 33 women completed 45 pregnancies, 44 singletons and 1 gemelli. In 24 (53%) of the cases, the mother had been treated with adjunctive stenting immediately following the CDT. In nine (21%) of the pregnancies, the mother had been on long-time anticoagulation treatment using warfarin prior to conception due to permanent severe risk factors. Thrombophilia was demonstrated in 31 (69%) of the pregnancies, and in 29 (64%) of the patients, the previous DVT was oestrogen-related. Thromboprophylaxis using tinzaparin was given in 41 (91%) and using dalteparin in four (9%) of the pregnancies. Doses of LMWH during pregnancy were adjusted according to risk assessment. One pregnancy was terminated by induced delivery at week 22 due to fetal malformations, and two of the pregnancies (4%) were complicated by intrauterine fetal death, one in week 39 due to severe fetal infection and one in week 23 due to intrauterine fetal growth restriction caused by severe antiphospholipid syndrome. All but one of the pregnancies was carried out without recurrence of DVT or maternal pulmonary embolism and the mother remained having patent deep veins postnatal. The mother with the antiphospholipid syndrome had a recurrent DVT complicated by iliac stent occlusion. This mother was prior to pregnancy on long-time treatment using warfarin. During pregnancy, she was erroneously treated with LMWH in standard prophylaxis doses instead of therapeutic doses and without adding aspirin.
Conclusions: After CDT for acute iliofemoral DVT including adjunctive stenting, pregnancy can be carried out almost uneventful even in women at high risk of thromboembolism. Thromboprophylaxis during pregnancy, using LMWH in a dosage adjusted to individual risk assessment, is essential.