Fetal critical aortic stenosis with natural improvement of hydrops fetalis due to spontaneous relief of severe restrictive atrial communication.

We describe a rare case of fetal critical aortic stenosis with spontaneous relief of severe restrictive atrial communication, resulting in complete resolution of hydrops fetalis in utero. Fetal ultrasonography showed hydrops fetalis caused by critical aortic stenosis with a severely restrictive foramen ovale and severe mitral regurgitation at 23 weeks of gestation. Hydrops fetalis, however, spontaneously resolved, showing an obvious increase of flow through the foramen ovale and pulmonary vein at 26 weeks of gestation. The neonate required balloon dilation of the aortic valve and balloon atrioseptostomy immediately after birth and also received bilateral pulmonary artery banding and arterial duct stenting 1 week later. The patient was in good condition after conversion to biventricular circulation via Ross procedure at 8 months old. The present case suggests that atrioseptostomy as a fetal intervention may improve outcome in even a hydropic condition.