Obstructed Labour

Note: Williams Obstetrics 26th Edition is not available in the digital library. The content below is drawn from authoritative obstetric references (Creasy & Resnik's Maternal-Fetal Medicine, ALARM International Program 4th Ed, Obstetrics Simplified by El-Mowafi) and reflects the standard content covered in Williams Obs 26e on this topic.

Definition

• Obstruction most commonly occurs at the pelvic brim, but may also occur in the pelvic cavity or at the outlet.
• Incidence: 1-3% of all labours.

Aetiology

Maternal Causes

• Contracted/small pelvis (most common in developing countries - due to childhood malnutrition, vitamin D deficiency, calcium deficiency)
• Deformed bony pelvis (rickets, trauma, kyphoscoliosis)
• Tumours of pelvic bones

• Uterus: impacted pedunculated fibroid, constriction ring at fetal neck
• Cervix: cervical dystocia (annular/rigid cervix)
• Vagina: vaginal septa, stenosis, tumours, scarring (e.g., female genital mutilation)
• Ovaries: impacted ovarian tumour

Fetal Causes (Cephalopelvic Disproportion)

• Face presentation (persistent mento-posterior)
• Brow presentation
• Shoulder/arm presentation (transverse lie)
• Breech (impacted frank breech)
• Compound presentation

• Persistent occipito-posterior (POP)
• Persistent occipito-transverse (deep transverse arrest)

• Hydrocephalus (most common)
• Fetal ascites
• Fetal abdominal/neck tumours (e.g., cystic hygroma, Wilms' tumour)
• Conjoined twins / locked twins

Pathophysiology

1. Formation of Bandl's retraction ring - a pathological retraction ring visible/palpable as an oblique groove across the abdomen, rising toward the umbilicus; it marks the junction between upper and lower uterine segments
2. Progressive thinning of the lower segment, predisposing to uterine rupture
3. Sustained pressure on bladder and rectum between fetal presenting part and maternal pelvis - leads to ischaemic necrosis and eventual vesicovaginal fistula (VVF) or rectovaginal fistula (RVF)

Clinical Features

History

• Prolonged labour (active phase >12 hours)
• Frequent, strong, painful uterine contractions
• Ruptured membranes (usually)

General Examination (Signs of Maternal Distress)

• Exhaustion and restlessness
• Dehydration: dry tongue, cracked lips, sunken eyes, oliguria
• Ketoacidosis: rapid pulse, deep rapid respiration (Kussmaul breathing), pyrexia, acetone in urine
• Tachycardia (pulse >100 bpm), pyrexia (≥38°C)
• Sepsis (late sign): purulent vaginal discharge, higher fever, tachycardia

Abdominal Examination

• Uterus is hard, tender, hypertonic
• Tetanic contractions (frequent, with little relaxation between)
• Pathological retraction ring (Bandl's ring): visible/palpable as an oblique groove rising toward the umbilicus - sign of impending rupture
• Fetal parts difficult to palpate
• Fetal heart sounds absent or showing fetal distress (variable decelerations, bradycardia)
• Bladder may be distended (urinary retention)

Vaginal Examination

• Vulva: oedematous
• Vagina: dry, hot
• Cervix: fully or partially dilated, oedematous, "hanging" (does not advance with contractions)
• Membranes: usually ruptured
• Presenting part: high, not engaged, or impacted
• If vertex: excessive moulding (overlapping skull bones) + large caput succedaneum
• Cause of obstruction can sometimes be directly identified

Diagnosis

• Cervical dilation crossing the action line (4 hours to the right of the alert line)
• Absent or arrested fetal descent

• Constriction ring (no excessive moulding, no Bandl's ring, cervix may be partially dilated)
• Full bladder causing apparent obstruction
• Fundal fibroid mimicking retraction ring

Complications

Maternal

Fetal

• Birth asphyxia (most common cause of perinatal mortality)
• Intracranial haemorrhage (from excessive moulding)
• Birth injuries (long bone fractures, nerve palsies)
• Neonatal sepsis
• Perinatal death

Management

Immediate Resuscitation (all cases)

1. IV access - two large bore cannulas
2. IV fluids - correct dehydration and ketoacidosis (Ringer's lactate or normal saline)
3. Catheterize - empty bladder (reduces obstruction, prevents fistula)
4. Antibiotics - broad spectrum (if membranes ruptured or signs of sepsis)
5. Analgesics/sedation as needed
6. Monitor fetal heart rate continuously

Definitive Treatment

• Lower segment is thinned and friable
• Any manipulation (forceps, internal version) risks rupture
• Even destructive operations risk maternal injury in an exhausted, infected uterus

• If the fetus is dead AND the obstruction is from the outlet AND the head is on the perineum - symphysiotomy or destructive operation may be considered at a centre without caesarean capability
• Vacuum extraction - only if head is at or below the spines and fully dilated, with experienced operator

Special Considerations

• In ruptured uterus - emergency laparotomy; repair or hysterectomy depending on findings
• In neglected obstructed labour with dead fetus - resuscitate first, then CS is still safer than destructive operations in most cases
• VVF prevention - catheterize bladder continuously for 10-14 days post-delivery to allow necrotic tissue to heal

Prevention

1. Adequate nutrition in childhood and adolescence (prevents contracted pelvis)
2. Antenatal assessment of pelvic adequacy (clinical pelvimetry)
3. Early identification of malpresentations and cephalopelvic disproportion (CPD) at antenatal visits
4. Partograph use for monitoring all labours - the single most effective tool
5. Skilled birth attendance - trained midwives/doctors who can recognise early obstruction
6. Referral systems - timely referral from community to facility

• Bandl's retraction ring is pathognomonic of obstructed labour and impending rupture
• In neglected obstructed labour, CS is safest even when fetus is dead
• The triad of prolonged labour + Bandl's ring + fetal distress = obstructed labour until proven otherwise
• Partograph's action line crossing is the trigger for active intervention
• "Obstructed Labour Injury Complex" = VVF + RVF + foot drop + chronic pelvic pain as long-term sequelae