Heart Defects Associated with Two-Vessel Umbilical Cord
Fetuses with a two-vessel (single umbilical artery) cord most commonly have ventricular septal defects, but also present with significant structural heart disease including hypoplastic left heart syndrome, coarctation of the aorta, and tetralogy of Fallot, with an overall cardiac malformation rate of approximately 9-13% 1, 2.
Cardiovascular System is Most Commonly Affected
When a single umbilical artery (SUA) is detected, the cardiovascular system represents the most frequently involved organ system for co-occurring structural abnormalities 3. The spectrum of cardiac defects ranges from simple septal defects to complex cyanotic lesions.
Specific Cardiac Defects by Frequency
The most commonly reported cardiac malformations include:
- Ventricular septal defect - the single most frequent cardiac anomaly 1
- Hypoplastic left heart syndrome - represents a significant proportion of complex defects 2
- Coarctation of the aorta 2
- Tetralogy of Fallot 1, 2
- Hypoplastic right heart syndrome 2
- Pulmonary atresia/stenosis 2
- Transposition of the great arteries 2
- Cardiac isomerism (both left and right) 2
Clinical Significance and Severity
Approximately half of the cardiac defects detected in fetuses with isolated SUA represent significant (major) heart disease 1. This is a critical distinction because these are not merely minor anatomical variants but potentially life-threatening structural abnormalities requiring specialized postnatal care.
Recommended Cardiac Evaluation
A comprehensive assessment of cardiac anatomy (CPT 76811 ultrasound) should be performed for all fetuses with SUA 3. The guideline specifies that if the required cardiac views are adequately visualized and normal on this comprehensive ultrasound, fetal echocardiography is not routinely warranted 3. However, given the 9-13% incidence of cardiac malformations and the severity of many defects, maintaining a low threshold for specialist cardiac evaluation is prudent.
Important Caveats:
- The presence of SUA with additional structural abnormalities dramatically increases aneuploidy risk (4-50%), whereas isolated SUA shows no increased aneuploidy risk 3
- Even when prenatal imaging appears normal, postnatal examination reveals structural anomalies in up to 7% of infants with prenatally diagnosed isolated SUA 3
- The pediatric provider must be notified at delivery about the prenatal SUA finding 3
Additional Non-Cardiac Considerations
Beyond cardiac defects, the renal system is the second most commonly affected organ system with SUA 3. Third-trimester growth surveillance and consideration of weekly antenatal testing beginning at 36 weeks is recommended due to associations with stillbirth and fetal growth restriction 3.