Usually, there is no self-repair of a fetal subtricuspid valve malformation. The lesions manifest as abnormal development of the tricuspid valve, enlargement of the annulus, downward displacement of the valve leaflets, and incomplete closure. It is difficult to repair on its own because of its structural abnormalities. In milder cases, the tricuspid valve may remain uncomfortable for life and may not require repair. In more severe cases, symptoms are more pronounced after birth, and about half of patients die within 2 years of age. In adulthood, some patients may gradually develop symptoms of heart failure, hypoxia, and arrhythmias. Therefore, if there is severe tricuspid valve insufficiency, cyanosis, or significant heart enlargement, prompt surgical treatment is recommended.