Mild fetal tricuspid regurgitation is one of the more common phenomena in obstetric ultrasound. The normal tricuspid valve closes during systole of the heart to prevent blood from flowing back to the right atrium during ventricular systole. When tricuspid regurgitation occurs, a regurgitant beam from the right ventricle can be detected in the tricuspid region during systole, which can be seen in abnormal fetuses as well as in normal fetuses. Physiologic tricuspid regurgitation often occurs in the fetus because lung tissue has not yet expanded, pulmonary artery pressure is mildly elevated, and the right cardiac systemic circulation is maintained by the ductus arteriosus and the patent foramen ovale, both of which are sustained on the basis of elevated pulmonary artery pressure. Tricuspid regurgitation is usually an isolated manifestation with slow regurgitation, low peak velocities, short duration of regurgitation, absence of malformations and other pathologic factors present, and no gestational effects on fetal health. Pathologic tricuspid regurgitation is systolic tricuspid regurgitation with a velocity greater than 80 cm/s and a duration of more than half a systole, and may be associated with fetal cardiac structural anomalies or noncardiac structural anomalies and other disorders. Therefore, mild tricuspid regurgitation requires further evaluation of the degree of regurgitation and a search for objective markers suggestive of hemodynamic abnormalities to correctly determine the cause of tricuspid regurgitation.