Background: Maternal New York Heart Association (NYHA) class is associated with pregnancy outcome in women with congenital heart disease (WCHD), but objective predictive criteria of exercise capacity have not been established. Methods and Results: A total of 33 WCHD (age, 28±5 years; NYHA class, 1.3±0.6) who had undergone cardiopulmonary exercise testing (CPX) 1.8±2.2 years before their delivery were retrospectively identified. Maternal, cardiac, and neonatal events occurred in 8 (24%), 12 (36%), and 14 (42%), respectively. All CPX parameters correlated with neonatal birth weight (P<0.05–0.001). Exercise time, peak heart rate (HR), peak systolic blood pressure, and peak oxygen uptake (VO₂) were associated with cardiac events (P<0.05–0.01), and exercise time and peak VO₂ were also associated with neonatal events (P<0.05). Exercise time, peak HR, and peak VO₂ were associated with at least 1 of the 3 events (P<0.05–0.01). Receiver operating characteristic analysis showed that peak HR <150beats/min and/or peak VO₂ <22.0ml·kg^–1·min^–1, peak VO₂ <26.2ml·kg^–1·min^–1, and peak HR <150beats/min and/or peak VO₂ <25.3ml·kg^–1·min^–1 predicted a high probability of maternal cardiac, neonatal, and maternal cardiac and/or neonatal event, respectively. Conclusions: CPX parameters predict pregnancy outcome and peak HR ≥150beats/min and/or peak VO₂ ≥25ml·kg^–1·min^–1 may be reference value(s) for a safer pregnancy outcome in WCHD.  (Circ J 2013; 77: 470–476)