What is the management approach for cord knots during labor?

Management of Umbilical Cord Knots During Labor

True umbilical cord knots require careful monitoring during labor, with prompt cesarean delivery indicated if signs of fetal distress appear. 1

Incidence and Risk Factors

• True umbilical cord knots occur in approximately 0.5% of vaginal deliveries, representing a relatively rare but potentially serious complication 2
• Cord knots can be either:
  • Single knots in singleton pregnancies
  • Entanglement of two umbilical cords in monoamniotic twins 1, 3
• Risk factors include excessive fetal movement, long umbilical cords (particularly those exceeding the 90th percentile of 69 cm), and monoamniotic twin pregnancies 2, 3

Diagnosis

• Prenatal diagnosis of true umbilical cord knots is challenging and often incidental 1
• Advanced ultrasound techniques improve detection rates:
  • 4D ultrasound with Color Doppler examination is the most effective diagnostic approach 4
  • Multiple views and repeated confirmation using color Doppler and power Doppler are necessary for accurate diagnosis 4
• Sonographic signs suggestive of cord knots include:
  • Visualization of the knot in multiple planes
  • Abnormal coiling pattern of the umbilical cord
  • Doppler flow changes before and after the suspected knot 4

Management Protocol

Antepartum Management

• When a true umbilical cord knot is diagnosed prenatally:
  • Institute weekly Doppler blood flow assessments in umbilical cord sections before and after the knot 4
  • Monitor for signs of intrauterine growth restriction (IUGR), which may occur due to altered fetal circulation 5
  • Pay particular attention to venous Doppler studies, as abnormalities may appear before arterial changes in cases of cord knots 5

Intrapartum Management

• Continuous electronic fetal monitoring is essential during labor 3
• Indications for immediate cesarean delivery include:
  • Variable fetal heart rate decelerations that suggest cord compression 3
  • Abnormal Doppler flow studies indicating cord constriction
  • Signs of acute fetal distress 3
• In the absence of fetal distress, vaginal delivery may be considered with close monitoring 2

Active Management of Third Stage

• After delivery of the infant, implement active management of the third stage:
  • Administer oxytocin immediately after delivery of the infant 6
  • Delay cord clamping for approximately three minutes to allow placental transfusion to complete 6
  • Follow with controlled cord traction for placental delivery 6
• This approach combines the benefits of delayed cord clamping with reduced risk of postpartum hemorrhage 6

Special Considerations

Monoamniotic Twins

• Monoamniotic twins have significantly higher risk of cord entanglement and knotting 3
• These pregnancies require more intensive surveillance:
  • More frequent ultrasound assessments
  • Earlier delivery consideration (typically 32-34 weeks) 3
  • Lower threshold for cesarean delivery when cord entanglement is identified 3

Growth-Restricted Fetuses

• Multiple true umbilical cord knots can cause severe fetal growth restriction 5
• A distinctive hemodynamic pattern may be observed:
  • Early alteration in fetal venous waveforms
  • Normal impedance in umbilical and uterine arteries until late stages 5
• This pattern should prompt careful evaluation of the umbilical cord 5

Clinical Pitfalls and Caveats

• Many cord knots remain undiagnosed prenatally, even with modern imaging techniques 4
• Not all cord knots lead to adverse outcomes; the tightness of the knot is a critical factor 1
• Absence of clinical warning signs (fetal distress) during pregnancy does not exclude the presence of a cord knot 2
• Distinguishing between true knots and false knots (localized redundancy of vessels) is important to avoid unnecessary interventions 4