9.3 Umbilical Cord Prolapse, Uterine Rupture & Amniotic Fluid Embolism

Umbilical Cord Prolapse, Uterine Rupture & Amniotic Fluid Embolism

Intrapartum obstetric practice demands instantaneous diagnostic acumen and coordinated multidisciplinary intervention when rare, life-threatening complications occur. Umbilical cord prolapse, uterine rupture, and amniotic fluid embolism (AFE) represent emergencies with extreme risks of sudden fetal demise and maternal mortality. Midwifery management is directed by national standards established by the Royal College of Obstetricians and Gynaecologists (RCOG Green-top Guideline No. 50 [Umbilical Cord Prolapse]) and national confidential maternal enquiry reports (MBRRACE-UK).

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Umbilical Cord Prolapse vs. Cord Presentation

Midwives must maintain a rigorous clinical distinction between cord prolapse and cord presentation:

• Cord Presentation: The umbilical cord lies below the fetal presenting part, between the presenting part and the cervix, with the fetal membranes intact.
• Umbilical Cord Prolapse (UCP): The umbilical cord descends through the cervix alongside (occult prolapse) or past (overt prolapse) the fetal presenting part into the vagina or protruding beyond the introitus in the presence of ruptured membranes.

                  CORD PRESENTATION vs. CORD PROLAPSE
                  
    [ CORD PRESENTATION ]                  [ OVERT CORD PROLAPSE ]
    
       Gravid Uterus                          Gravid Uterus
      /             \                        /             \
     (  Fetal Head   )                      (  Fetal Head   )
      \             /                        \             /
       === CORD ===                           === CORD === (Compressed!)
       ~~~~~~~~~~~~ [Membranes Intact]        ──────────── [Membranes Ruptured]
          Cervix                                 Cervix
            ||                                     || === CORD in Vagina ===

Pathophysiology & Urgency

When membranes rupture and the cord prolapses, the cord is subjected to severe mechanical compression between the advancing fetal presenting part and the maternal bony pelvis. Furthermore, exposure to the cooler ambient temperature of the vagina or external environment triggers acute, violent vasospasm of the umbilical arteries and vein. This obliterates fetoplacental gas exchange, leading to profound hypoxia, rapid acidosis, terminal bradycardia, and intrauterine death within minutes if not relieved immediately.

Clinical Risk Factors

Any condition that prevents the presenting part from fitting snugly into the lower uterine segment and maternal pelvic inlet predisposes to cord prolapse:

• Malpresentations: Transverse, oblique, or unstable lie; breech presentation (highest with footling breech [15%–18%], followed by flexed breech [5%–10%]; lowest with frank/extended breech [0.5%]); compound presentation.
• Unengaged Presenting Part: High fetal head at onset of spontaneous labour or rupture of membranes.
• Iatrogenic Factors: Artificial Rupture of Membranes (ARM) performed when the presenting part is unengaged (station > -2) or mobile; fetal scalp electrode placement; external cephalic version (ECV).
• Polyhydramnios: Sudden gush of amniotic fluid following spontaneous or artificial membrane rupture carries the cord downward through the cervix.
• Fetal Factors: Prematurity (<37 weeks), low birth weight (<2,500 g), multiple gestation (especially following the delivery of the first twin, where the second twin remains unengaged).
• Long Umbilical Cord: Cords exceeding 75–80 cm in length.

Diagnostic Recognition

• Direct Palpation / Visualisation: A soft, coiled, pulsating loop of cord is palpated on digital vaginal examination or observed protruding at the vulva.
• Sudden Severe FHR Bradycardia: An acute, prolonged fetal heart rate deceleration (<100 bpm) or recurrent, deep, atypical variable decelerations occurring immediately following spontaneous or artificial rupture of membranes.

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Emergency Protocol for Umbilical Cord Prolapse

Immediate management follows a strict physical and surgical rescue sequence:

1. Call for Immediate Help: Pull the emergency bell and dial 2222 to mobilize the obstetric emergency team (obstetrician, anaesthetist, senior midwife, neonatal resuscitation team, and theatre staff).
2. Manual Elevation of the Presenting Part: The midwife immediately inserts a sterile, gloved hand into the vagina and pushes the fetal presenting part upward and away from the umbilical cord, relieving mechanical compression against the pelvic brim. This manual elevation must be maintained continuously without releasing pressure, including throughout patient transfer to theatre, until the operating obstetrician delivers the fetus at caesarean section.
3. Maternal Positioning: Reposition the woman to allow gravity to shift the fetus away from the pelvis:
   • Exaggerated Sims Position: Left lateral position with head flat, pelvis elevated on 2 to 3 firm pillows, and upper leg flexed.
   • Knee-Chest Position (All-Fours): The woman kneels on the bed with her chest flat on the mattress and buttocks elevated high in the air.
   • Trendelenburg Tilt: Tilting the delivery bed head-down.
4. Avoid Handling the External Cord:

1. Retrograde Bladder Filling (The Vago Technique):
   • If transfer to an operating theatre is delayed or if transfer from a community/home setting is required, insert an indwelling Foley catheter.
   • Instil 500 mL to 750 mL of warm sterile 0.9% sodium chloride into the bladder via a giving set, then clamp the catheter.
   • The distended bladder acts as a physical hydraulic wedge, pushing the lower uterine segment and fetal presenting part cephalad off the pelvic brim.
   • Ensure the bladder is rapidly drained via the catheter immediately prior to the surgical skin incision.
2. Mode of Delivery:
   • Category 1 Emergency Caesarean Section: The definitive standard of care, with a decision-to-delivery target interval of ≤30 minutes (and ideally within 15 minutes).
   • Exception: If the cervix is fully dilated, the fetal head is deeply engaged (+2 or +3 station), and delivery is imminent, immediate assisted vaginal birth (ventouse or forceps) may be conducted by an experienced obstetrician in the delivery room.

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Uterine Rupture

Uterine rupture is a catastrophic, full-thickness breach of the myometrial wall involving the overlying visceral peritoneum, creating a direct communication between the uterine cavity and the peritoneal cavity. It must be distinguished from uterine dehiscence (an incomplete scar separation where the visceral peritoneum remains intact, often clinically silent).

Clinical Risk Factors

• Previous Caesarean Section: The single most significant risk factor. A previous classical (vertical midline) uterine incision carries a 4% to 9% rupture risk; a previous lower segment transverse incision carries a 0.5% to 0.7% risk during Vaginal Birth After Caesarean (VBAC).
• Previous Uterine Surgery: Transmural myomectomy, metroplasty, or perforation during curettage.
• Oxytocic Hyperstimulation: Inappropriate titration of intravenous oxytocin (Syntocinon) or off-label use of prostaglandins (e.g. misoprostol or dinoprostone) in a scarred uterus.
• High Parity: Grand multiparity (parity ≥5).
• Obstructed Labour and neglected cephalopelvic disproportion.

Diagnostic Hallmark Signs

Midwives caring for women undergoing VBAC or high-risk labours must maintain vigilant surveillance for the clinical constellation of uterine rupture:

Emergency Management

• Call the 2222 obstetric emergency team immediately.
• Immediate Category 1 Emergency Laparotomy under general anaesthesia to deliver the fetus and control catastrophic haemorrhage.
• Aggressive fluid and blood product resuscitation under the Major Haemorrhage Protocol.
• Surgical repair of the myometrial defect or emergency peripartum hysterectomy if the rupture is extensive or involves the uterine vessels.

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Amniotic Fluid Embolism (AFE)

Amniotic Fluid Embolism (AFE), also termed anaphylactoid syndrome of pregnancy, is an unpredictable, devastating obstetric emergency characterized by a catastrophic maternal systemic inflammatory and immunological reaction triggered by the entry of amniotic fluid and fetal antigenic material (squames, lanugo, meconium) into the maternal endocervical or uterine venous circulation.

Classical Clinical Presentation Triad

AFE typically presents during advanced labour, caesarean delivery, or within the immediate 30 minutes postpartum with a sudden, catastrophic triad:

                  ┌──────────────────────────────────────────┐
                  │    AMNIOTIC FLUID EMBOLISM (AFE) TRIAD   │
                  └────────────────────┬─────────────────────┘
                                       │
         ┌─────────────────────────────┼─────────────────────────────┐
         ▼                             ▼                             ▼
┌─────────────────┐           ┌─────────────────┐           ┌─────────────────┐
│  ACUTE HYPOXIA  │           │ CARDIOVASCULAR  │           │   CONSUMPTIVE   │
│                 │           │    COLLAPSE     │           │  COAGULOPATHY   │
│ • Sudden dyspnoea│          │ • Sudden arrest │           │ • Fulminant DIC │
│ • Tachypnoea    │           │ • Profound shock│           │ • Intractable   │
│ • Cyanosis      │           │ • Right heart   │           │   haemorrhage   │
│ • SpO2 <85%     │           │   failure       │           │ • Oozing wounds │
└─────────────────┘           └─────────────────┘           └─────────────────┘

1. Acute Respiratory Arrest & Hypoxia: Sudden-onset severe dyspnoea, cough, tachypnoea, bronchospasm, profound cyanosis, and rapid desaturation to <85%.
2. Acute Cardiovascular Collapse & Shock: Sudden profound hypotension, acute right-sided heart failure with pulmonary arterial hypertension, and rapid progression to cardiac arrest (often pulseless electrical activity [PEA] or asystole).
3. Fulminant Consumptive Coagulopathy / DIC: Intractable, uncontrollable haemorrhage from the genital tract, intravenous puncture sites, surgical incisions, and mucosal surfaces, driven by massive consumption of fibrinogen and platelets triggered by tissue factor in amniotic fluid.

Resuscitation & Critical Care Management

• ABCDE Resuscitation: Immediate high-flow oxygen, rapid tracheal intubation with 100% O2, and invasive arterial and central venous monitoring.
• Haemodynamic Inotropic Support: Early administration of noradrenaline, adrenaline, and milrinone to support right ventricular function and overcome pulmonary hypertension.
• Aggressive MHP Activation: Massive transfusion of PRBCs, platelets, FFP, and early Cryoprecipitate (aiming to keep fibrinogen >2.0 g/L), alongside Tranexamic Acid (1 g IV).
• Resuscitative Hysterotomy: If maternal cardiac arrest occurs after 20 weeks, preparation for resuscitative hysterotomy starts immediately, and RCUK 2025 guidance advises performing it as soon as possible at the site of arrest if there is no prompt ROSC (older teaching used a 4-minute decision / 5-minute delivery rule).