Prenatal diagnosis of Type II single umbilical artery (persistent vitelline artery) in a normal fetus

Abstract

The human umbilical cord usually develops with two arteries and one vein. However, in 0.5–1% of fetuses, one umbilical artery is either obliterated or simply does not form, giving rise to single umbilical artery (SUA) syndrome1-3. Although several mechanisms have been proposed to explain the pathogenesis of SUA, in most cases it is due to secondary atresia or atrophy of one or both previously normal umbilical arteries1. Blackburn and Cooley2 suggested four plausible types of SUA (Figure 1). Type II SUA is the second most frequent and is thought to occur secondary to fusion of the two umbilical arteries. It is normally reported in malformed fetuses with sirenomelia, or after interruption in the development of both umbilical arteries accompanied by persistent vitelline artery, which compensates for this defect2, 3. We report a favorable outcome after prenatal diagnosis of Type II SUA in a normal fetus. A 31-year-old primigravida was referred to our center at 22 weeks' gestation after a routine ultrasound scan revealed SUA and abnormal abdominal vasculature without other malformations. Umbilical arteries could not be seen in their normal position adjacent to the bladder, and a large artery was observed continuing in an anterior direction towards the umbilical cord, inferior to the celiac trunk at the position of the superior mesenteric artery (SMA) with normal blood flow indices (Figure 2). The umbilical vein appeared normal and blood flow in the abdominal aorta, renal and femoral arteries was also normal. The pregnancy was uneventful and at 40 weeks' gestation, the patient gave birth via vaginal delivery to a healthy female infant weighing 4010 g. The appearance of the placenta was normal, and the umbilical cord had a single artery with a distinct internal elastic lamina, usually absent in normal umbilical arteries on histopathological testing. Differentiation between SUA types is a prenatal diagnostic challenge, and most isolated cases are considered to be Type I. Using color Doppler ultrasound, after obtaining an axial view of the fetal ventral wall, umbilical arteries can be tracked as they divide to enclose the fetal bladder. However, in Type II SUA, both umbilical arteries are absent. The sagittal view at the abdominal–pelvic level confirms the diagnosis, because the artery observed in the umbilical cord originates directly and abnormally from the aorta, inferior to the celiac trunk and at the position of the SMA. The artery follows an abnormal course separated from the bladder (Figure 2)2, 3. Diagnosis of SUA syndrome should be followed by an exhaustive fetal morphology scan, though fetal karyotype testing is not mandatory in isolated cases4. Type II SUA can be associated with sirenomelia or defects of the viscera and/or soft tissues, or it may be present as an isolated finding1, 5. In the latter instance, clinical presentation of the neonate after birth could be normal or could be associated with acute intestinal obstruction, recurrent intestinal pain, or intra-abdominal hemorrhage. Based on surgical findings, Postoloff6 described three types of persistent vitelline artery: a persistent band between the anterior abdominal wall and the ileal mesentery, a band in association with Meckel's diverticulum, or a free-hanging cord. However in this case, neonatal outcome was favorable, and after 12 months of follow-up the infant remained asymptomatic. F. Gámez†, J. De León-Luis*†, C. Bravo†, P. Pintado†, Y. Ruiz‡, S. Palomo§, R. Pérez† and L. Ortiz-Quintana† †Fetal Medicine Unit, Department of Obstetrics and Gynecology, Hospital General Universitario Gregorio Marañón, Calle O'Donnell, 48, Planta 0, Bloque C, 28009 Madrid, Spain; ‡Department of Radiology, Hospital General Gregorio Marañón, Universidad Complutense de Madrid, Madrid, Spain; §Department of Pathology, Hospital General Gregorio Marañón, Universidad Complutense de Madrid, Madrid, Spain *Correspondence. (e-mail: [email protected]) This work was supported by Fondo de Investigaciones Sanitarias (FIS# PI081712 and BA#09/90011). We are grateful to Mr David De León for assistance with graphics and to Mr Thomas O'Boyle for editorial assistance.