Why does umbilical cord (UC) prolapse pose a risk of death to the baby?

Why Umbilical Cord Prolapse Risks Death in a Baby

Umbilical cord prolapse is a life-threatening obstetric emergency that risks fetal death primarily due to compression of the umbilical cord between the fetal presenting part and the maternal pelvis, leading to acute interruption of fetal blood supply and oxygen. 1, 2

Pathophysiology of Cord Prolapse and Fetal Death

• Cord compression during prolapse causes immediate interruption of placental blood flow to the fetus, resulting in rapid fetal hypoxia and acidosis 3
• The umbilical cord contains vital blood vessels (two arteries and one vein) that are the fetus's only source of oxygen and nutrients; compression of these vessels during prolapse can quickly lead to severe fetal compromise 1
• Cord arterial pH declines significantly during prolonged cord compression at a rate of approximately 0.009 per minute, indicating progressive fetal acidosis 3
• Bradycardia (severe slowing of fetal heart rate) is often observed with cord prolapse, signaling critical compromise of fetal circulation 2

Risk Factors for Cord Prolapse

• Fetal malpresentation (particularly breech or transverse lie) significantly increases risk 4
• Prematurity and low birth weight are major predisposing factors 4
• Multiple pregnancy increases risk due to altered fetal positioning 4
• Polyhydramnios (excess amniotic fluid) creates conditions where the cord can easily slip below the presenting part 2
• Iatrogenic causes account for up to 50% of cases, including procedures such as amniotomy (artificial rupture of membranes) 2

Physiological Impact on the Fetus

• The stress of birth already represents one of life's most critical physiological transitions, requiring significant cardiopulmonary adaptation 5
• Normal transition from fetal to neonatal life depends on intact umbilical circulation until breathing is established 5
• When cord prolapse occurs, the fetus experiences:
  • Acute hypoxia (oxygen deprivation)
  • Rapid development of acidosis
  • Potential for irreversible brain damage or death if not promptly addressed 3

Timing and Mortality Risk

• Perinatal mortality from cord prolapse ranges from 6-10% in high-income countries to 23-27% in low-income countries 3
• The diagnosis-to-delivery interval is critical, with optimal outcomes when delivery occurs within 30 minutes of diagnosis 2
• Prolonged bradycardia during cord prolapse is particularly dangerous, as it may indicate irreversible pathology such as vasospasm or persistent complete cord compression 3

Management to Prevent Fetal Death

• Immediate recognition and intervention are essential to prevent fetal death 1
• Emergency delivery (usually by cesarean section) is the definitive management 6
• While awaiting delivery, measures to relieve cord compression include:
  • Manual elevation of the presenting part
  • Maternal positioning (knee-chest position provides greatest elevation effect)
  • Bladder filling with 500 mL of fluid (Vago's method) 3
• Excessive manipulation of the cord should be avoided to prevent cord spasm, which can further compromise fetal circulation 2

Critical Considerations

• The location where prolapse occurs significantly impacts outcomes - hospital settings allow for more rapid intervention 2
• Simulation training for healthcare providers improves management and documentation of this emergency 2
• Prompt diagnosis coupled with appropriate neonatal resuscitation capabilities significantly improves outcomes 5, 2

Understanding the pathophysiology of cord prolapse helps explain why this obstetric emergency requires immediate recognition and intervention to prevent the potentially fatal consequences of prolonged fetal hypoxia.