Although venous thromboembolism (VTE) is the leading cause of maternal mortality in developed countries, the usefulness of preventive low-molecular-weight heparin (LMWH) after cesarean delivery remains a matter of controversy. It was the objective of this study to evaluate the usefulness of thromboprophylaxis with LMWH after cesarean delivery. A decision model was constructed to evaluate the risks and benefits associated with a seven-day LMWH prophylaxis, compared with none. All probabilities were obtained from literature according to the highest level of evidence. We performed our analysis on two different sets of outcomes (utilities and disutilities), to calculate the quality-adjusted life expectancy at three months. Finally, we calculated the outcomes for four hypothetical cases with different risk. Prophylaxis with LMWH yielded the highest quality-adjusted life expectancy, with a net gain of 1.5-2.8 quality-adjusted days. Sensitivity analyses showed the incidence of VTE after cesarean delivery and the haemorrhagic risk related to LMWH to be critical, at threshold values of 0.15-0.22% and 0.23-0.35%, respectively. In the hypothetical cases, LMWH was safe but only marginally more effective in women with no risk factors. In case of an emergency procedure, a body-mass index >25kg/m(2), tobacco smoking, or any combination of these, reductions in VTE greatly outnumbered the increase in major haemorrhages, with a modest benefit on mortality. Our decision analysis suggests that the benefits of LMWH after cesarean delivery exceed the risks. This benefit is, however, very low in women with no risk factors.