Prenatal diagnosis of isolated foramen ovale obstruction. A report of two cases.

Premature obstruction of the foramen ovale is a rare but serious clinical entity. Obstruction can be associated with right ventricular failure, fetal hydrops, tricuspid regurgitation, left heart obstructive defects and supraventricular tachycardia. In most cases, the diagnosis is made at the postmortem examination. The etiology is unknown. We discuss 2 prenatal cases with the sole diagnosis of ventricular asymmetry. The right ventricle was dilated and hypertrophic, and the foramen ovale ballooned into the left atrium without color Doppler detection of right-to-left flow. After delivery, the infants had no hydrops or symptoms of cardiac or respiratory distress. Echocardiography demonstrated a structurally normal heart with increased right ventricle dimensions until the 7th day of life. Delivery should be induced if possible in cases of foramen ovale obstruction with signs of cardiac decompensation.