Résumé : Background Postoperative bleeding and blood product transfusion increase morbidity, mortality, and costs after cardiac surgery. However, factors that could accurately predict bleeding have not been well studied in children undergoing cardiac surgery. This study aims at determining factors that could be used to predict postoperative bleeding in this paediatric population. Methods We included 182 children undergoing congenital heart surgery. Significant bleeding was defined as a blood loss that exceeds 10% of total blood volume within the first 6 postoperative hours. Univariate and multivariate logistic regression analyses were performed to determine variables independently associated with bleeding. These variables were used to calculate a probability for each individual child to develop postoperative bleeding. Results According to the definition of bleeding, 44 patients were included into the 'bleeder' group and 138 into the 'non-bleeder' group. Factors independently associated with postoperative bleeding were preoperative body weight, the presence of a cyanotic disease, and the time required for wound closure. Based on these three parameters, we calculated the probability of bleeding and found a significant relationship with postoperative bleeding. Finally, a calculated probability of 0.59 can predict significant postoperative blood loss with a sensitivity of 84% and a specificity of 64%. Conclusions This study shows that preoperative body weight, cyanotic disease, and wound closure duration are best predictors of bleeding in the paediatric population after cardiac surgery. The combination of these three factors could be used at the end of the surgery to estimate the probability of postoperative bleeding. ? The Author [2013].