Umbilical vein anomaly in fetuses with Down syndrome.

OBJECTIVE

To describe the prevalence of abnormal umbilical vein (UV) anatomy in fetuses with Down syndrome.

METHODS

This was a retrospective survey covering a 24-month period of fetuses with a genetic diagnosis of Down syndrome following a routine early second-trimester (12-16-week) detailed fetal anomaly scan at a single academic tertiary referral center. In our unit this exam includes fetal umbilicoportal venous system evaluation.

RESULTS

During the study period, 37 fetuses were diagnosed with Down syndrome and had a detailed early anatomy scan. In four (11%) the detailed early anomaly scan revealed that the UV was connected to the hepatic portion of the inferior vena cava (IVC) at a position lower than its usual site. Their average gestational age at diagnosis was 13 + 6 (range, 11 + 6 to 15 + 2) weeks. Three of the four fetuses had a nuchal translucency thickness of 3-4 mm. In one fetus there was an additional finding of significant tricuspid regurgitation and the one with normal nuchal translucency thickness had an atrioventricular septal defect (atrioventricular canal) and umbilical cord hernia. During the same period three of 2500 (0.12%) fetuses with normal karyotype demonstrated similar anomalous insertion of the UV into the IVC, creating a portocaval shunt which had normal ductus venosus-like Doppler flow in all three cases. The odds ratio for abnormal umbilicoportal venous system in fetuses with Down syndrome compared with the normal population was 107.4 (95% CI, 19.2-637.1).

CONCLUSIONS

Fetuses with Down syndrome demonstrate an increased prevalence of abnormal connection of the UV to the IVC.