What is permanent right umbilical vein The permanent right umbilical vein is a developmental anomaly of the fetal vascular system in which the left umbilical vein is atretic in an individual during fetal life and the right umbilical vein persists and participates in fetal blood circulation. In a normal fetus, the right umbilical vein degenerates and atresizes during the fourth week of gestation and disappears at approximately the seventh week of gestation. This means that the permanent right umbilical vein is a variation of the vascular anatomy and not a fetal malformation, meaning that the right umbilical vein, which is supposed to degenerate, does not degenerate, while the left umbilical vein, which is not supposed to degenerate, does. The incidence is about 0.2% to 1%. What should I do if I find a permanent right umbilical vein in my fetus? The vast majority of persistent right umbilical veins do not combine with fetal anomalies, but only a few may combine with fetal anomalies such as hydrocephalus, single umbilical artery, short limb, atrial septal defect, ventricular septal defect, aortic constriction, tracheoesophageal fistula, hypospadias, renal displacement, visceral inversion, abnormal bowel rotation, and anorectal malformation. Pure persistent right umbilical vein without other abnormalities is often a benign variant with a good prognosis. Once combined with other malformations, the prognosis often depends on the malformation. Therefore, if a persistent right umbilical vein is detected on ultrasound, the venous catheter should be carefully examined to follow the course of the umbilical vein and venous catheter to see if it is connected to the inferior vena cava. Other areas should also be carefully examined. In cases of combined malformations, chromosomal examination is required and pregnancy should be terminated if the karyotype is abnormal.