Although the number of pregnancies in women with cardiac disease is increasing worldwide, there are few data concerning their clinical characteristics and peripartum outcomes. Using the Diagnosis Procedure Combination database between 2008 and 2014 in Japan, we retrospectively identified pregnant women who underwent high-risk delivery due to obstetric or non-obstetric comorbidities. We classified eligible women into those with pre-existing cardiac disease (cardiac disease group) and those with non-cardiac comorbidities (non-cardiac disease group) and compared their characteristics and peripartum outcomes. Of 94,364 women undergoing high-risk delivery at 556 hospitals, 857 (0.91%) had pre-existing cardiac disease (302, congenital heart disease; 190, arrhythmia; 176, valvular heart disease; 120, ischemic heart disease; 65, cardiomyopathy; 4, pericardial disease). Women in the cardiac disease group were more likely to be treated at university hospitals (51.1 versus 28.6%; p < 0.001) and in intensive care units (33.5 versus 18.8%; p < 0.001) than those in the non-cardiac disease group. The proportion of cesarean deliveries was 69.4% (emergency, 28.4%; elective, 41.1%) in the cardiac disease group and 73.4% (emergency, 38.4%; elective, 35.0%) in the non-cardiac disease group. Epidural analgesia during vaginal delivery was used significantly more frequently in the cardiac disease than non-cardiac disease group (15.6 versus 2.3%; p < 0.001). Heart failure occurred more frequently in the cardiac disease than the non-cardiac disease group (10.2 versus 0.3%; p < 0.001). In cardiac subgroup comparisons, heart failure occurred more frequently in women with congenital heart disease (12.3%), valvular heart disease (12.5%), or cardiomyopathy (12.3%) than in women with arrhythmia (6.3%) or ischemic heart disease (5.8%). Multivariable logistic regression analysis showed a significant positive association between pre-existing cardiac disease and risk of heart failure (adjusted odds ratio, 24.7; 95% confidence interval, 17.6–34.6; p < 0.001). No woman in the cardiac disease group died, whereas 18 women (0.02%) in the non-cardiac disease group did (p = 1.000). These findings suggest that pregnant women with pre-existing cardiac disease are at a higher risk of heart failure during the peripartum period than those with non-cardiac comorbidities.