Single umbilical artery

Please note that some guidelines may be past their review date. The review process is currently paused. It is recommended that you also refer to more contemporaneous evidence.

A single umbilical artery (SUA) is a malformation of the umbilical cord where only one artery instead of two is present. It may be associated with other birth defects.

The pathogenesis of an SUA is thought to be secondary to vessel atrophy of a previously normal cord in the mid trimester. Sometimes a rudimentary second artery is seen histologically (although, the prognostic implications of this are unclear).

Antenatal diagnosis may be impeded by fetal position.

The first postpartum screening programs for SUA were established in 1955 in obstetric centres following the discovery of an association with other congenital abnormalities.

Diagnosis

Diagnosis after birth is by either gross or histological examination of the cord (concordance between the two is good).

Obstetric complications

Possible complications associated with single umbilical artery include:

• Fifty per cent of fetuses with antenatally diagnosed SUA have associated chromosomal or congenital malformations (typically cardiac, neurological, renal). Two-thirds of these had Trisomy 18.
• Virtually any abnormality has been associated with SUA rather than any specific syndromes.
• SUA is associated with an increased perinatal mortality rate of 22 per cent because of the association with congenital malformations.
• Isolated SUA is associated with IUGR (10 per cent versus 4.4 per cent with a three-vessel cord).

Paediatric complications

Paediatric complications associated with single umbilical artery include:

• An isolated SUA is associated with renal malformations in 7-9 per cent of infants. Vesicoureteric reflux (VUR) is the most common abnormality occurring in 4 per cent of infants with an isolated SUA.
• In a meta analysis of 26 studies the incidence of any renal abnormality associated with isolated SUA was 8 per cent, with only 4 per cent requiring treatment of the abnormality. From this meta analysis the investigation of 14 cases of isolated SUA would yield one patient requiring treatment.
• In another study VUR was also the most common abnormality requiring treatment and three out of five of their patients had a urinary tract infection (UTI) before the age of three months.

Management

Management of single umbilical artery involves the following:

• Prenatal management of a single umbilical artery cord includes:
  • thorough antenatal scan and fetal echocardiogram
  • consider chromosome analysis (particularly if another soft marker for aneuploidy is noted).
• Isolated SUA should have close clinical follow up to assess intrauterine growth with repeat ultrasound scans as indicated clinically.
• Postnatal examination aims to exclude congenital abnormalities especially cardiac, neurological and renal.
• Infants born with SUA without associated abnormalities should have a routine postnatal examination.
• Follow-up should include a renal ultrasound unless adequate antenatal ultrasound imaging of the kidneys is available.
• A micturating cystourethrogram to exclude vesico-ureteric reflux should be considered (as a small proportion of infants with VUR will have a normal renal ultrasound).