A term infant rapidly developed profound cyanosis and metabolic acidosis shortly after an uncomplicated vaginal delivery. Echocardiography identified a flail antero-superior leaflet of the tricuspid valve, which was producing severe tricuspid insufficiency. The clinical state deteriorated despite maximal medical management, and the patient was placed on venoarterial extracorporeal membrane oxygenation. Within twenty-four hours, the metabolic acidosis corrected, inotropic support was discontinued, and the patient was weaned to minimal ventilator settings. Successful repair of the tricuspid valve was performed two days later.