Background: Pregnancy in women with congenital heart disease (CHD) is associated with increased risk for maternal cardiac complications. Several risk stratification models are used to predict adverse cardiac outcome in women with CHD who become pregnant. This study was set up as an exploratory study to provide a head-tohead comparison of the 4 most commonly used models: CARPREG, CARPREG II and ZAHARA risk scores and mWHO risk classification. Methods and results: We randomly selected 100 women from the database of paediatric and congenital heart disease of the University Hospitals Leuven. Individual pregnancy risk scores were retrospectively calculated and summarized in a weighted average risk for each risk stratification model. To evaluate accuracy of each model, the weighted average risk was plotted against the actual observed number of "cardiac events" as defined in the respective risk models. Maternal adverse cardiac events occurred in 8% of our study population. Weighted average risks were plotted versus the observed number of events for each model: 10.1% versus 4.0% for CARPREG, 8.6% versus 5.0% for CARPREG II, 11.1% versus 8.0% for ZAHARA and 12.4% versus 8.0% for the mWHO classification. Conclusion: All risk models overestimated maternal cardiac risk. The ZAHARA risk model appeared to be a closer reflection of maternal risk in our cohort of CHD patients. More research on a larger study population is needed.