Umbilical vein insertion into the inferior vena cava: an ominous sign of chromosomal abnormalities?

This series describes the sonographic characteristics and pregnancy outcomes of fetuses with abnormal insertion of the umbilical vein (UV) into the inferior vena cava (IVC). We conducted a retrospective study that described the sonographic features of 6 patients who underwent a routine anatomic scan during early pregnancy. Six patients had a diagnosis of abnormal insertion of the UV to the IVC; in 3, the diagnosis was made at 12 weeks' gestation. Cardiac anomalies were detected in 3 patients, including ventricular septal defects, pericardial effusion, tricuspid and mitral regurgitation, and an aberrant right subclavian artery. Four had noncardiac anomalies, including cystic hygroma and skeletal, brain, and abdominal anomalies. Only 1 fetus who presented with UV insertion into the IVC as an isolated finding had a normal karyotype, resulting in term vaginal delivery. Four other patients had chromosomal abnormalities, including trisomies 13 and 21, Turner mosaicism of 45,XO/46,XY, and Robertsonian translocation, and 1 patient terminated the pregnancy without a karyotype evaluation. Abnormal insertion of the UV into the IVC with agenesis of the ductus venosus can be seen as early as the first trimester. When detected, a detailed anatomic examination should be performed, as well as a fetal karyotype evaluation. Isolated cases of insertion of the UV into the IVC at a position lower than usual may have a good prognosis.