Abstract Background Management of pregnancy and risk stratification in women with congenital heart diseases (CHD) are challenging especially due to physiological haemodynamic modifications that inevitably occur during pregnancy. Objective To compare the accuracy of the existing pregnancy cardiovascular risk scores in prediction of maternal complications during pregnancy in CHD patients. Method From 2007 to 2018, all pregnant women with a CHD who delivered birth after 20 weeks of gestation were identified. The discriminating power and the accuracy of the five existing pregnancy cardiovascular risk scores (CARPREG, CARPREG II, HARRIS, ZAHARA risk scores, and modified WHO (mWHO)) were evaluated. Results Out of 104 pregnancies in 65 CHD patients, 29% experienced cardiovascular complications during pregnancy or postpartum. For the five scores, the observed rate of cardiovascular events was higher than the expected risk. The values of area under the ROC curve were 0.75 [0.62;0.88] for mWHO, 0.65 [0.53;0.77] for CARPREG II, 0.60 [0.40;0.80] for HARRIS, 0.59 [0.47;0.72] for ZAHARA, and 0.58 [0.43;0.73] for CARPREG. Conclusion The modified WHO classification appeared to better predict cardiovascular outcome in pregnant women with CHD than the four other existing risk scores. Clinical Trial Registration: Clinicaltrials.gov: NCT04221048.