Alterations of the ductus arteriosus, e.g. occlusion, constriction or aneurysm, can influence the fetal and neonatal circulation. A case of fetal right atrial and ventricular dilatation, severe tricuspid valve insufficiency and transient pulmonary valve regurgitation at 32 weeks of gestation is reported. Structural heart defects and extracardiac diseases (e.g. high output cardiac failure in arteriovenous shunts and anemia) were excluded by Doppler echocardiography and fetal blood sampling. An abnormally S-shaped kinking of the ductus arteriosus with increased systolic and diastolic flow velocities in the distal part was demonstrated. At 35 weeks' gestation, Cesarean section was performed, because of increased tricuspid valve insufficiency, and a healthy boy was born. After birth, right heart dilatation and tricuspid valve insufficiency decreased. The cardiac changes in relation to the anatomical abnormality of the ductus arteriosus are discussed.