It is present in just under 1% of singleton deliveries, with absence of the left umbilical artery more common (requires antenatal ultrasound).
A neonate whose placenta had 1 umbilical artery ("two vessel cord") is at risk for:
(1) genitourinary anomalies, ranging from vesicuourethral reflux to major malformations
(2) cardiovascular anomalies
(3) musculoskeletal anomalies
(4) chromosomal abnormalities, especially if multiple anomalies are present
(5) small for gestational age (SGA, intrauterine growth retardation)
A neonate with a single umbilical artery should be screened for defects and monitored more closely. If no problems are found then the conditions is termed "isolated."
