What is the management plan for a pregnancy with a two-vessel (umbilical) cord?

Management of Two-Vessel Umbilical Cord (Single Umbilical Artery)

When a two-vessel umbilical cord is identified, perform a comprehensive anatomic ultrasound focusing on cardiac and renal systems, obtain third-trimester growth ultrasounds, and initiate weekly antenatal surveillance at 36 weeks for isolated cases. 1

Initial Diagnostic Evaluation

Upon identification of a single umbilical artery (SUA), immediate assessment should focus on:

• Perform a detailed anatomic survey with particular attention to cardiovascular and renal systems, as these are the most commonly affected organ systems 1
• Assess for cardiac anomalies through standard views; fetal echocardiography is not routinely required if cardiac views are adequately visualized and normal 1
• Evaluate for additional structural abnormalities to distinguish isolated from non-isolated SUA 1

Risk Stratification for Aneuploidy

The approach to genetic testing depends critically on whether SUA is isolated:

• For isolated SUA: No additional aneuploidy evaluation is recommended, regardless of prior screening results or whether screening was declined 1
• For non-isolated SUA (with structural abnormalities): Aneuploidy risk ranges from 4% to 50%, warranting genetic counseling and consideration of diagnostic testing 1
• Karyotyping is specifically recommended when SUA occurs with symmetric growth restriction or any other structural defect 2

A critical pitfall: Even when ultrasound shows SUA with one visible anomaly, additional major structural defects are frequently missed on prenatal imaging—in one series, 9 of 27 fetuses with sonographically detected abnormalities had additional unrecognized major defects 2

Surveillance Protocol for Fetal Growth

Third-trimester ultrasound is mandatory to evaluate fetal growth, as SUA carries significant risk for growth restriction 1:

• Growth restriction occurs in approximately 7 of 38 (18%) chromosomally normal fetuses with isolated SUA 2
• Serial growth assessments should be performed at intervals no less than every 2 weeks, with 3-4 week intervals providing more reliable measurements given inherent biometric error 3
• Once growth restriction is diagnosed, initiate serial umbilical artery Doppler assessment to monitor for deterioration 1

Antenatal Surveillance Strategy

For isolated SUA without growth restriction:

• Begin weekly cardiotocography (CTG) testing at 36 0/7 weeks of gestation 1
• If growth restriction develops, start weekly CTG after viability 1
• Increase surveillance frequency when growth restriction is complicated by abnormal Doppler findings or other comorbidities 1

The rationale for heightened surveillance: Population-based studies demonstrate SUA is associated with a nearly 5-fold increased odds of stillbirth (OR 4.80; 95% CI 2.67-8.62) 1, along with elevated risks of oligohydramnios, placental abruption, and cord prolapse 1

Doppler Assessment Protocol

When growth restriction is identified:

• Weekly umbilical artery Doppler with decreased end-diastolic velocity or severe growth restriction (estimated fetal weight <3rd percentile) 3
• Doppler assessment 2-3 times weekly when absent end-diastolic velocity (AEDV) is detected due to potential for rapid deterioration 3
• In the setting of reversed end-diastolic velocity (REDV): Hospitalization, antenatal corticosteroids, and CTG at least 1-2 times daily 3

Timing of Delivery

For isolated SUA without growth restriction: Standard obstetric management applies for timing of delivery 1

When growth restriction develops, delivery timing is dictated by Doppler findings 1:

• 38-39 weeks: Normal umbilical artery Doppler with estimated fetal weight 3rd-10th percentile 3, 1
• 37 weeks: Decreased diastolic flow without AEDV/REDV, or severe growth restriction (estimated fetal weight <3rd percentile) 3, 1
• 33-34 weeks: Absent end-diastolic velocity 3, 1
• 30-32 weeks: Reversed end-diastolic velocity 3, 1

Mode of Delivery Considerations

• Cesarean delivery should be considered for pregnancies with growth restriction complicated by AEDV/REDV based on the complete clinical picture 3
• Antenatal corticosteroids are indicated if delivery is anticipated before 33 6/7 weeks, or between 34 0/7 and 36 6/7 weeks in women at risk of delivery within 7 days who have not received a previous course 3
• Intrapartum magnesium sulfate for neuroprotection is recommended for pregnancies <32 weeks 3

Postnatal Management

• Notify the pediatric provider of prenatal findings at delivery 1
• Postnatal examination is essential: Structural anomalies have been revealed in up to 7% of infants with prenatal diagnosis of isolated SUA 1
• Postnatal renal ultrasound and physical examination are typically sufficient for screening genitourinary abnormalities; additional imaging such as voiding cystourethrogram may be considered if abnormalities are detected 4

Critical Pitfalls to Avoid

• Do not assume isolated SUA on initial scan means truly isolated: Four additional major anomalies were diagnosed postnatally among 45 chromosomally normal fetuses with no visible defects on prenatal ultrasound 2
• Do not defer growth surveillance: Growth restriction risk persists even with isolated SUA and normal anatomy 2
• Do not overlook the stillbirth risk: The nearly 5-fold increased odds necessitates third-trimester surveillance even in apparently uncomplicated cases 1