What is the management of a pregnancy with a two-vessel (2V) umbilical cord?

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

For pregnancies with a two-vessel umbilical cord (single umbilical artery), a detailed anatomical ultrasound and third-trimester growth scan are recommended, followed by weekly antenatal fetal surveillance beginning at 36 weeks of gestation due to increased risk of fetal growth restriction and stillbirth. 1

Incidence and Etiology

  • Single umbilical artery (SUA) occurs in 0.25% to 1% of singleton pregnancies and up to 4.6% of twin gestations 1
  • SUA results from either atrophy or agenesis of one of the two normal umbilical arteries 1
  • Can be detected on cross-section of the umbilical cord during routine second-trimester ultrasound or using color flow Doppler to examine umbilical arteries in the fetal pelvis 1

Initial Evaluation

  • A comprehensive assessment of fetal anatomy should be performed when SUA is identified 1
  • Particular attention should be paid to the cardiovascular and renal systems, as these are the most common sites of associated anomalies 1
  • If required cardiac views are adequately visualized and normal, fetal echocardiography is not routinely warranted 1

Risk Assessment

Isolated SUA vs. SUA with Other Abnormalities

  • Isolated SUA: No other structural or chromosomal abnormalities present
  • Non-isolated SUA: SUA present with other structural abnormalities

Aneuploidy Risk

  • SUA with one or multiple structural abnormalities: Associated aneuploidy risk ranges from 4% to 50% 1
  • Isolated SUA: No increased risk of aneuploidy 1, 2
  • Recommendation: For fetuses with an isolated SUA, no additional evaluation for aneuploidy is recommended, regardless of whether previous aneuploidy screening results were low risk or screening was declined 1

Growth Restriction and Stillbirth Risk

  • Evidence regarding the association between isolated SUA and fetal growth restriction (FGR) is conflicting 1
  • Some studies show increased risk of FGR, while others suggest no increased risk 1, 2
  • In a population-based case-control study, SUA was associated with an increased odds ratio of stillbirth compared with live birth (OR 4.80; 95% CI 2.67-8.62) 1
  • Other studies have demonstrated increased risks of FGR, oligohydramnios, placental abruption, cord prolapse, and perinatal mortality in fetuses with SUA 1

Recommended Management Protocol

Ultrasound Surveillance

  • A detailed obstetrical ultrasound examination (CPT code 76811) should be performed to rule out associated anomalies 1
  • Third-trimester ultrasound examination is recommended to evaluate fetal growth 1
  • If FGR is diagnosed, serial umbilical artery Doppler assessment should be performed to assess for deterioration 1

Antenatal Testing

  • Consider weekly antenatal fetal surveillance beginning at 36 0/7 weeks of gestation for fetuses with an isolated SUA 1
  • If FGR is diagnosed, weekly cardiotocography testing is suggested after viability 1
  • The frequency of testing should be increased if FGR is complicated by absent/reversed end-diastolic velocity or other comorbidities 1

Timing of Delivery

  • For isolated SUA without FGR: Standard obstetric management for timing of delivery
  • If FGR develops:
    • With normal umbilical artery Doppler and EFW between 3rd-10th percentile: Delivery at 38-39 weeks 1
    • With decreased diastolic flow but without absent/reversed end-diastolic velocity or with severe FGR (EFW <3rd percentile): Delivery at 37 weeks 1
    • With absent end-diastolic velocity: Delivery at 33-34 weeks 1
    • With reversed end-diastolic velocity: Delivery at 30-32 weeks 1

Postnatal Considerations

  • The pediatric provider should be notified of the prenatal findings at the time of delivery 1
  • Postnatal examination is important as structural anomalies have been revealed in up to 7% of infants with a prenatal diagnosis of isolated SUA in one study 1

Clinical Pitfalls and Caveats

  • Umbilical artery thrombosis may present as an SUA on ultrasound when there were previously two arteries visualized; this requires immediate attention as it can lead to fetal hypoxia and death 3
  • The presence of SUA in combination with complex umbilical cord entanglement (such as true knots or multiple nuchal cords) may warrant consideration for earlier delivery due to increased risk of adverse outcomes 4
  • Do not confuse SUA with other umbilical cord abnormalities such as nuchal cords, which have different management implications 5, 4

By following this management protocol, clinicians can appropriately monitor pregnancies with two-vessel umbilical cords and intervene when necessary to improve perinatal outcomes.

References

1
Guideline

Guideline Directed Topic Overview

Dr.Oracle Medical Advisory Board & Editors, 2025

2
Research

Prenatal diagnosis of the two-vessel cord: implications for patient counselling and obstetric management.

Ultrasound in obstetrics & gynecology : the official journal of the International Society of Ultrasound in Obstetrics and Gynecology, 1995

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Professional Medical Disclaimer

This information is intended for healthcare professionals. Any medical decision-making should rely on clinical judgment and independently verified information. The content provided herein does not replace professional discretion and should be considered supplementary to established clinical guidelines. Healthcare providers should verify all information against primary literature and current practice standards before application in patient care. Dr.Oracle assumes no liability for clinical decisions based on this content.

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