Birth outcomes in pregnant women treated with low-molecular-weight heparin

Background. Pregnancy and puerperium are associated with an increased risk of venous thromboembolism. Low-molecular-weight heparin is the anticoagulan t of choice in pregnant women because, unlike warfarin, it does not cross t he placenta. However, there are limited data on the risk of adverse birth o utcomes following use of low-molecular-weight heparin in pregnancy. Patients and methods. We performed a population-based cohort study to exami ne the safety of low-molecular-weight heparin use in pregnancy using data f rom the Pharmacoepidemiological Prescription Database, The Danish Medical B irth Registry and the Regional Hospital Discharge Registry in North Jutland County, Denmark. The birth outcomes in a cohort of 66 pregnant women treat ed with low-molecular-weight heparin between 1991-98 were compared with the birth outcomes of 17,259 pregnant women who did not receive any prescripti ve drugs during pregnancy. Results. No increased risk of malformations, low birth weight or stillbirth was found. However, an increased risk of pre-term delivery was found (odds ratio: 2.11, 95% confidence interval: 0.96-4.65), which could reflect inhe rited thrombophilia as an indication of low-molecular-weight heparin. Conclusion. We have provided additional evidence of the safety of low-molec ular-weight heparin use in pregnancy.