This is a multicentre, randomized, double-blind, placebo controlled study. During this study all the patients will receive background venous thromboembolism (VTE) mechanical prophylaxis with intermittent pneumatic compression (IPC).

This is a multicenter, randomized, double-blind, placebo-controlled study evaluating the safety and efficacy of fondaparinux in the prevention of venous thromboembolism (VTE) in subjects undergoing abdominal surgery at increased risk for VTE. During this study all subjects were to receive background VTE prophylaxis with intermittent pnuematic compression (IPC) ± elastic stockings (ES).

Screening Period ( Day -30-Day 0) all subjects at increased risk of VTE undergoing abdominal surgery and fulfilled the study entry criteria were eligible for the study.

Treatment Period (Day 7 ±2): At the baseline assessment on the day of surgery (Day 1) subjects who satisfied all inclusion/exclusion criteria were randomized (1:1) to receive either fondaparinux or placebo. All the subjects were to receive background therapy with IPC ±ES. The first administration of either fondaparinux 2.5mg or placebo was to take place 6 to 8 hours after surgical closure provided hemostasis was achieved. Thereafter a once daily subcutaneous injection of either fondaparinux 2.5mg or placebo was to be administered up to Day 7 ±2. During the treatment phase, subjects were assessed daily. A mandatory venogram was performed between Day 5 and 10 or earlier in the case of symptomatic VTE, but not more than 1 calendar day after the last study treatment administration.

Follow up Period (Day 30 ±2): A follow-up visit or contact was to take place at Day 30 ±2 days. Use of antithrombotic therapy for prevention of VTE after the mandatory venographyand during the entire Follow-up Period was left to the investigator's discretion.

Inclusion Criteria:

• Undergoing abdominal surgery (any surgery between the diaphragm and pelvic floor) lasting longer than 45 minutes (duration from anesthesia induction to surgical closure)
• Over 40 years of age
• Subject who had signed the informed consent.

Exclusion Criteria:

• Active, clinically significant bleeding
• Documented congenital or acquired bleeding tendency/disorders
• Active ulcerative gastrointestinal disease unless the reason for the present surgery.
• Recent intracranial hemorrhage or recent (less than 3 months prior to randomisation) brain, spinal, or ophthalmologic surgery.
• Indwelling intrathecal or epidural catheters for more than 6 hours after surgical closure.
• Subjects who had a traumatic puncture or unusual difficulty in applying the catheter
• Known cerebral metastasis,
• Subjects in whom hemostasis had not been established 6 hours after surgical closure,
• Current thrombocytopenia,
• Bacterial endocarditis
• Creatinine level above 2.0 mg/dL (180 μmol/L) in a well-hydrated subject,
• Documented hypersensitivity to contrast media,
• Use of any contraindicated drug that could not be combined with the injection of contrast medium,
• Patent with evidence of leg ischemia caused by peripheral vascular disease, unable to undergo IPC and unable to wear Elastic Stockings.

Exclusion criteria related to trial methodology:

• Mental disorders that could interfere with study participation and/or failure to give written informed consent to take part in the study,
• Subject's life expectancy < 6 months,
• Clinical sign of DVT and/or history of recent DVT,
• Participation in any other therapeutic drug study or a device study evaluating DVT prophylaxis within 90 days preceding inclusion,
• Previous participation in a study of fondaparinux sodium,
• Known hypersensitivity to fondaparinux and its excipients,
• Current addictive disorders that could interfere with study participation,
• Administration of heparin, heparinoids, LMWH, oral anticoagulants, dextrans, hirudin, fibrinolytic agents or drugs blocking glycoprotein platelet receptors (GPIIb-IIIa) during the screening period, i.e., from admission to surgery,
• Subjects for whom anticoagulant therapy was contraindicated or who had, due to concomitant disease, an indication for oral anticoagulant or heparins (including LMWH) and who could not discontinue those treatments,
• Women of child-bearing potential: women not using an appropriate contraceptive method during the whole duration of study participation ,
• Subject with body weight <50 kg,
• Subjects, who in the opinion of the investigator, required a pharmacological prophylaxis in addition to intermittent pneumatic compression,
• Known pregnancy and / or women who intended to breastfeed,
• Subjects undergoing vascular surgery such as aorto-femoral bypass graft

Patient-level data for this study will be made available through www.clinicalstudydatarequest.com following the timelines and process described on this site.