ETIOLOGY OF SINGLE UMBILICAL ARTERY (SUA)

Three theories have been proposed (1):

1. Primary agenesis of one umbilical artery (theory not thought to be justifiable) (2).
2. Persistence of the original allantoic artery of the body stalk (theory not thought to be justifiable) (2).
3. Secondary atrophy or atresia of a previously normal umbilical artery (the most plausible theory) (2). This results in a single umbilical artery in an otherwise normal infant and probably develops after day 42 of gestation.

Rosenak and Meizner (3) have reported a single case in which a SUA and normal three vessel cord has been encountered in the same fetus.
Persutte (4) has demonstrated a similar finding. At pathological examination "the second umbilical artery was dysplastic, with intermittent severe hypoplasia and intraluminal bridging to the other artery".
Convergence of two arteries into one occurs more frequently at the placental insertion.

REFERENCES

1. Romero R, Pilu G, Jeanty P et.al. Single umbilical artery. In Prenatal Diagnosis of Congenital Anomalies p.387. Norwalk: Appleton and Lange.
2. Persutte WH, Hobbins J. Single umbilical artery: a clinical enigma in modern prenatal diagnosis. Ultrasound Obstet Gynecol 1995;6:216-229.
3. Rosenak D, Meizner I. Prenatal sonographic detection of single and double umbilical artery in the same fetus. J Ultrasound Med 1994;13:995-996.
4. Persutte WH. Single fetal umbilical artery: a case report illustrating a potential pitfall in the diagnosis. J Diag Med Sonography 1994;10:161-163.