Venous thromboembolism during pregnancy: a retrospective study of enoxaparin safety in 624 pregnancies

Objective To assess the maternal, fetal and neonatal safety of enoxaparin in pregnant women who require antithrombotic therapy.

Design Retrospective analysis of case notes of women who received enoxaparin during pregnancy, irrespective of dose, duration and reason for treatment.

Setting Fifty-five French perinatal centres.

Sample Data from 624 pregnancies in 604 women between 1988 and 1997. The incidence of previous thromboembolism was 29.8%, known thrombophilia 15.2%.

Methods Indication, regimen of enoxaparin and outcome measures were reported for each pregnancy. Information was obtained from case records, validated by research staff and analysed by an independent scientific committee.

Main outcome measures Incidence, seriousness and causality of maternal, fetal and neonatal adverse events, pregnancy outcome, and incidence of venous thromboembolism.

Results Enoxaparin was administered for treatment of an acute episode in 49 cases and for thromboprophylaxis in 574 cases. Serious maternal haemorrhage occurred in 11 cases during pregnancy (1.8%), one being reasonably related to enoxaparin, and in nine cases at delivery (1.4%), all unrelated to enoxaparin. Maternal thrombocytopenia was reported in 10 cases (1.6%), two being serious but unrelated to enoxaparin. Eight pregnancies ended in stillbirth (1.1%). Among the 693 live births, 17 major congenital abnormalities (2.5%) and 10 serious neonatal haemorrhages (1.4%) were reported. None of the fetal or neonatal adverse events was related to enoxaparin. Eight venous thromboembolic events (1.3%) were reported.

Conclusions The incidence of adverse events reported could be explained by the high risk profile of the study population. Overall, this retrospective study suggests enoxaparin is well tolerated during pregnancy.