AbstractObjectiveOur objective was to evaluate the incidence of a persistent right umbilical vein in isomerism versus situs solitus.MethodsFor this retrospective, observational, nonrandomized report, we identified fetuses with confirmed right umbilical veins from all patients referred for fetal echocardiography in Southern Nevada between January 2006 and January 2019.ResultsFor the period January 2006 to January 2019, we identified 89 fetuses with situs solitus and a right umbilical vein from 16 320 women undergoing prenatal cardiac evaluation, resulting in a right umbilical vein incidence of 0.5% in situs solitus. For the same period, we identified 36 fetuses with isomerism and confirmatory umbilical vein imaging. Of the 36, 15 (42%) had right umbilical veins. Of the 15, four of 11 (19%) had left isomerism, and 11 of 15 (73%) had right isomerism (P = .006).ConclusionsA right umbilical vein is rare with situs solitus and common with isomerism. A right umbilical vein is more common in right isomerism than left isomerism and should alert the clinician to check for isomeric situs, especially right isomerism.