Maternal and fetal outcomes in women with fontan circulation: a retrospective cohort from a brazilian tertiary referral center (2012–2025)

Introduction The number of patients with congenital heart disease who reach adulthood has increased substantially over recent decades, and recent data show that up to 97% of patients now survive into adulthood. Among women with univentricular physiology, approximately 80% are also reaching reproductive age, and many wish to pursue motherhood. However, despite all advances, these patients are still considered high risk (mWHO 2.0 class III and mWHO 2.0 class IV), with maternal and fetal outcomes that remain uncertain after pregnancy. Pregnancy itself imposes a significant hemodynamic burden, including increased circulating blood volume and decreased systemic vascular resistance, and the consequences of these physiological changes in patients with Fontan circulation are not always predictable and may vary from case to case. Data in the literature regarding this specific patient population, both in terms of maternal and fetal outcomes, remain limited. Materials and Methods This retrospective cohort study included all pregnancies in patients with Fontan physiology who were followed at a tertiary care center in São Paulo, Brazil, between 2012 and 2025. From the time of pregnancy diagnosis until the outcome—whether miscarriage, delivery, obstetric hospitalization or admission due to cardiovascular decompensation—patients were evaluated in outpatient visits with the cardio-obstetrics team every 15 to 21 days and subsequently followed for up to 12 months postpartum. Antithrombotic therapy with aspirin or low-molecular-weight heparin was individualized on a case-by-case basis. Results A total of 25 pregnancies in 19 patients were followed. 9 pregnancies ended in miscarriage (36%), with 7 occurring in the first trimester and 2 in the second trimester (up to 19 weeks). Most newborns were preterm (69%) and had low birth weight (75%). There were no maternal deaths, and obstetric complications were infrequent compared with data reported in the literature (no cases of preeclampsia, one case of subchorionic hematoma, and one case of intrahepatic cholestasis of pregnancy). Preexisting cardiac arrhythmia was associated with a higher incidence of preterm birth, and ventricular dysfunction prior to pregnancy was associated with worse functional class 12 months postpartum. Conclusion In this single-center cohort, pregnancy in Fontan patients was associated with a high rate of fetal complications, miscarriage, prematurity, and low birth weight, while maternal mortality was absent and obstetric complications were relatively infrequent. Preexisting cardiac arrhythmia and baseline ventricular dysfunction emerged as important markers of adverse outcomes, influencing perinatal results and late maternal functional status. These findings reinforce that pregnancy in patients with Fontan circulation remains high risk and requires careful preconception counseling, individualized risk stratification, and close multidisciplinary follow-up.Pre-gestagional systolic function