Praxis Medical Insights

Est. 2024 • Clinical Guidelines Distilled

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Last Updated: 12/30/2025

Management of Two-Vessel Umbilical Cord in Pregnancy

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: No other structural or chromosomal abnormalities present 1
  • Non-isolated SUA: SUA present with other structural abnormalities 1
  • SUA with one or multiple structural abnormalities: Associated aneuploidy risk ranges from 4% to 50% 1
  • Isolated SUA: No increased risk of aneuploidy 1
  • The American College of Obstetricians and Gynecologists recommends that 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

  • 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 fetal growth restriction, oligohydramnios, placental abruption, cord prolapse, and perinatal mortality in fetuses with SUA 1
  • A detailed obstetrical ultrasound examination should be performed to rule out associated anomalies 2
  • Third-trimester ultrasound examination is recommended to evaluate fetal growth 1
  • If fetal growth restriction is diagnosed, serial umbilical artery Doppler assessment should be performed to assess for deterioration 3
  • Consider weekly antenatal fetal surveillance beginning at 36 0/7 weeks of gestation for fetuses with an isolated SUA 1
  • If fetal growth restriction is diagnosed, weekly cardiotocography testing is suggested after viability 3
  • The frequency of testing should be increased if fetal growth restriction is complicated by absent/reversed end-diastolic velocity or other comorbidities 3

Timing of Delivery

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

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

Management of Single Umbilical Artery

Surveillance and Monitoring

  • 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, as recommended by the American College of Radiology 4
  • Weekly umbilical artery Doppler is recommended when growth restriction is identified, with decreased end-diastolic velocity or severe growth restriction, according to the American Journal of Obstetrics and Gynecology 5
  • Doppler assessment 2-3 times weekly is recommended when absent end-diastolic velocity is detected due to potential for rapid deterioration, as suggested by the American Journal of Obstetrics and Gynecology 5
  • In the setting of reversed end-diastolic velocity, hospitalization, antenatal corticosteroids, and CTG at least 1-2 times daily are recommended, as advised by the American Journal of Obstetrics and Gynecology 5

Timing of Delivery

  • For pregnancies with growth restriction, delivery timing is dictated by Doppler findings, with normal umbilical artery Doppler and estimated fetal weight 3rd-10th percentile recommending delivery at 38-39 weeks, as suggested by the American Journal of Obstetrics and Gynecology 5
  • Decreased diastolic flow without AEDV/REDV, or severe growth restriction, recommends delivery at 37 weeks, according to the American Journal of Obstetrics and Gynecology 5
  • Absent end-diastolic velocity recommends delivery at 33-34 weeks, as advised by the American Journal of Obstetrics and Gynecology 5
  • Reversed end-diastolic velocity recommends delivery at 30-32 weeks, as recommended by the American Journal of Obstetrics and Gynecology 5

Mode of Delivery Considerations

  • Cesarean delivery should be considered for pregnancies with growth restriction complicated by AEDV/REDV based on the complete clinical picture, as suggested by the American Journal of Obstetrics and Gynecology 5
  • 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, as recommended by the American Journal of Obstetrics and Gynecology 5
  • Intrapartum magnesium sulfate for neuroprotection is recommended for pregnancies <32 weeks, as advised by the American Journal of Obstetrics and Gynecology 5

Management of Single Umbilical Artery in Pregnancy

Clinical Significance and Associated Risks

  • The American College of Obstetricians and Gynecologists recommends hospital admission if fetal surveillance more often than 3 times per week is deemed necessary, in the setting of single umbilical artery 6, 7

Management When Growth Restriction Develops

  • The American College of Obstetricians and Gynecologists suggests weekly umbilical artery Doppler evaluation when decreased end-diastolic velocity or severe fetal growth restriction is present, in the setting of single umbilical artery 6, 7

Hospitalization Criteria

  • Hospitalization is recommended in the setting of reversed end-diastolic velocity, with administration of antenatal corticosteroids and performance of cardiotocography at least 1-2 times daily, according to the American College of Obstetricians and Gynecologists 6, 7

Management of Isolated Single Umbilical Artery in Pregnancy

Fetal Surveillance and Doppler Monitoring

  • In pregnancies with isolated SUA that develop fetal growth restriction (FGR), serial umbilical artery Doppler studies should be performed to detect hemodynamic deterioration; when decreased end‑diastolic velocity (flow ratios > 95th percentile) or severe FGR (estimated fetal weight < 3rd percentile) is present, weekly Doppler assessments are recommended. 8
  • If absent end‑diastolic velocity is identified, Doppler examinations should be increased to 2–3 times per week to closely track worsening placental perfusion. 8
  • When reversed end‑diastolic velocity occurs, hospitalization, administration of antenatal corticosteroids, and cardiotocography at least once‑to‑twice daily are advised to optimize fetal outcomes. 8
  • For FGR without absent or reversed end‑diastolic flow, weekly cardiotocography (CTG) after fetal viability should be performed. 8
  • If FGR is complicated by absent/reversed end‑diastolic velocity or additional maternal/fetal comorbidities, the frequency of CTG should be increased (e.g., more than once weekly) to allow timely detection of distress. 8

Delivery Timing Recommendations

  • When the estimated fetal weight is between the 3rd and 10th percentile and umbilical artery Doppler is normal, delivery is recommended at 38–39 weeks’ gestation. 8
  • If there is decreased diastolic flow without absent/reversed end‑diastolic velocity or the fetus meets criteria for severe FGR (EFW < 3rd percentile), delivery should be planned at 37 weeks. 8
  • In the presence of absent end‑diastolic velocity, delivery is advised at 33–34 weeks to balance the risks of prematurity against ongoing placental insufficiency. 8
  • When reversed end‑diastolic velocity is detected, delivery is recommended at 30–32 weeks because of the high risk of fetal demise. 8

Adjunctive Therapies and Mode of Delivery

  • Cesarean delivery should be considered for pregnancies with FGR complicated by absent or reversed end‑diastolic velocity, taking into account the overall clinical picture and maternal preferences. 8
  • Antenatal corticosteroids are indicated when delivery is anticipated before 33 6⁄7 weeks, and also between 34 0⁄7 and 36 6⁄7 weeks in women who are at risk of delivering within the next 7 days. 8
  • Intrapartum magnesium sulfate for fetal neuroprotection is recommended for pregnancies under 32 weeks’ gestation when early delivery is planned. 8

REFERENCES

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