OBJECTIVE: Pregnancies in patients with adult congenital heart disease (ACHD) are often complicated. We aimed to highlight the nature and the rate of these complications in a single-center patient population.METHODS: We retrospectively studied all the pregnancies of women who presented on an outpatient basis, and all pregnancies were reviewed for maternal and fetal outcomes.RESULTS: Of 117 pregnancies from 52 ACHD patients (age at pregnancy 28.3 ± 6.6 years), 10 were therapeutically aborted. A proportion of 41.1% of the remaining 107 pregnancies were complicated either with cardiac (3.7%), obstetric (15.0%), or fetal/neonatal (11.2%) adverse events or with spontaneous abortion (17.8%). Hospitalization during pregnancy was required in 10 patients. Elective cesarean sections were initially planned for 31% of the 87 pregnancies, which were finally completed, while 8% required an emergency cesarean section, mostly for obstetric reasons. NYHA class deterioration after pregnancy was detected in 9.3% of our cohort. Modified WHO class III/IV, prior medication use, and higher body mass index (BMI) were related to cardiac complications during pregnancy or NYHA deterioration.CONCLUSION: Pregnancies in ACHD patients are at high risk for complications. Advanced modified WHO class, prior medication use, and high BMI were related to adverse cardiac events.