Functional and imaging outcomes of the Fontan circulation following pregnancy

The Fontan circulation palliates single-ventricle congenital heart disease by separating the systemic and pulmonary circulations. An increasing number of women with a Fontan circulation are wishing to become pregnant, however the ability to increase cardiac output during pregnancy is limited in many due to the chronic low output state. We describe pregnancy outcomes in these women at a large tertiary centre, including functional and imaging outcomes.

We retrospectively investigated women with a Fontan circulation giving birth after 24 weeks' gestation between 1995 and 2023. Data collected included obstetric and neonatal complications, changes in cardiac volumes and ejection fraction (EF), and functional outcomes including change in NYHA class and exercise capacity pre- and post-pregnancy, compared to matched male controls.

Twenty-six pregnancies occurred among 23 women. Almost half experienced obstetric complications, primarily bleeding, which was the commonest indication for emergency C-section. Worsening cardiac symptoms complicated 50 % of pregnancies, with 4 requiring hospital admission for decompensation. Arrhythmias were not uncommon. Mean VO_2max declined post-pregnancy (p = 0.03), though not significantly compared to controls. Worsening of NYHA class was uncommon (15.4 %), suggesting that cardiovascular complications during pregnancy do not correlate with longer-term functional limitation. EF worsened post-pregnancy, declining significantly more so than in matched controls (p = 0.03), however there were no changes in cardiac volumes.

Pregnancy in women with a Fontan circulation is associated with high rates of obstetric complications and worsening cardiac symptoms. However, successful pregnancies are possible, with little evidence of medium-term functional impairment. This data informs pre-pregnancy counselling of Fontan women of child-bearing age.