This prospective observational study reports on 126 women from 25 UK centres with image-proven antenatal venous thromboembolism (VTE), 62% deep vein thrombosis and 38% pulmonary embolism. Thrombophilia screening was of limited benefit except to identify antithrombin deficiency. Sixteen (13%) patients had previous VTE, all but one was related to previous pregnancy or combined oral contraceptive and 12 received no thromboprophylaxis in the index pregnancy, the other four thus received inadequate low molecular weight heparin (LMWH) doses. Treatment was with dalteparin in 25%, enoxaparin in 47%, tinzaparin in 25% and unfractionated heparin alone in 3%. 66% of patients received once-daily LMWH. Anti-activated factor X (anti-Xa) monitoring was performed at 90% of centres, with a wide range of target values. Thus current management of antenatal VTE, despite widely diverse clinical practice, appeared effective and safe, for there were no recurrent events and postpartum haemorrhage was not increased when compared to known rates. Larger studies are required to confirm this. The need for twice as opposed to once daily LMWH and for anti-Xa monitoring is questioned by this study. The importance of clinical risk assessment and adherence to the Royal College of Obstetricians and Gynaecologists guidelines on antenatal thromboprophylaxis, with adequate LMWH dosing is confirmed.