Abnormal Labour and Delivery

Abnormal labour covers any deviation from the expected progress of labour, and includes dystocia (slow or arrested progress), precipitate labour, malpresentation and malposition, shoulder dystocia, cord prolapse, and uterine rupture. The classical mechanical framework is the "3 Ps": power (uterine contractions and maternal effort), passenger (fetal size, presentation, position and attitude), and passage (pelvis and soft tissues).

Normal progress by stage:

• Latent phase: from onset of regular painful contractions to about 4 to 6 cm of dilation. Can last up to 20 hours in nulliparas and 14 hours in multiparas
• Active phase: from 6 cm (modern thresholds; older practice used 4 cm). Expected rate in modern data is about 1 cm per 1 to 2 hours, with slower progress up to 6 cm being normal
• Second stage: from full dilation to birth. Nulliparous women: up to 3 hours without epidural (4 hours with epidural); multiparous women: up to 2 hours (3 hours with epidural)
• Third stage: up to 30 minutes with active management

Dystocia is the commonest indication for primary caesarean delivery. Diagnostic criteria for active phase arrest: cervix 6 cm or more dilated, ruptured membranes, and no cervical change for 4 hours with adequate contractions (more than 200 Montevideo units), or 6 hours with inadequate contractions despite oxytocin. Second stage arrest: no descent or rotation despite good maternal effort for the time limits above.

Causes:

• Inadequate uterine activity (hypotonic dysfunction): most common cause of slow labour, treated with oxytocin
• Cephalopelvic disproportion: macrosomia, contracted pelvis, hydrocephalus
• Malposition: occipito posterior (persistent OP in about 5 to 10%), occipito transverse arrest, deflexed head
• Malpresentation: breech, face, brow, shoulder, compound
• Soft tissue obstruction: fibroids, cervical stenosis, ovarian tumour, full bladder
• Maternal factors: obesity, advanced age, exhaustion, dehydration, anxiety, epidural analgesia

Precipitate labour is expulsion within 3 hours of onset of contractions. It risks cervical and perineal tears, postpartum haemorrhage, uterine rupture, and neonatal injury.

Evaluation of labour progress relies on regular partogram plotting of:

• cervical dilation
• descent of the fetal head (station or fifths palpable abdominally)
• contraction frequency, strength and duration
• fetal heart rate
• maternal vital signs
• liquor colour
• moulding and caput

Signs of obstructed labour:

• prolonged labour with a pushed up Bandl ring (retraction ring)
• oedematous cervix
• severe caput and moulding (3+ moulding, overriding sutures)
• distressed mother with tachycardia and fever
• concentrated urine or haematuria
• fetal compromise

Untreated, obstruction leads to uterine rupture.

Specific complications:

• Shoulder dystocia: failure of delivery of the shoulders after the head, in 0.2 to 3% of births, with the "turtle sign" (head retracts against perineum).
• Risk factors for shoulder dystocia include fetal macrosomia (above 4,500 g), maternal diabetes, previous shoulder dystocia, obesity, post-term pregnancy and operative vaginal delivery.
• Fetal consequences of shoulder dystocia: brachial plexus injury (Erb palsy), clavicle and humeral fracture, hypoxic injury if head-to-body interval is long
• Cord prolapse: cord descends below the presenting part, risk factors are malpresentation, polyhydramnios, preterm labour, artificial rupture of membranes with a high head; fetal bradycardia is the classical sign
• Uterine rupture: sudden fetal distress, loss of station, abdominal pain, vaginal bleeding, scar tenderness; risk 0.5 to 1% after previous low transverse caesarean in trial of labour, higher with a classical scar or with oxytocin or prostaglandins
• Postpartum haemorrhage (PPH), perineal trauma, chorioamnionitis, and obstetric fistula in neglected obstructed labour

Confirm that the labour is genuinely established and that membranes and fetal heart tracing are reviewed. For each case of slow progress, do an assessment of the "3 Ps":

• Power: palpation or tocodynamometry; intrauterine pressure catheter if available and the diagnosis is uncertain
• Passenger: abdominal palpation for presentation and engagement, vaginal examination for position (fontanelles and sutures), ultrasound for suspected OP or breech, and estimated fetal weight
• Passage: clinical pelvimetry; assess caput and moulding, which can falsely indicate descent

Exclude fetal compromise through cardiotocography, with fetal scalp lactate (above 4.8 mmol/L abnormal, 4.1 to 4.8 borderline) where available. Check maternal hydration, ketones, bladder, temperature and infection.

Slow progress in the first stage.

• Confirm adequate hydration, empty bladder, mobility and upright positions, effective analgesia, and continuous support
• Amniotomy if membranes are intact and the head is well applied
• Oxytocin augmentation after 2 hours of slow progress (or on diagnosis) in a nullipara and in multiparas after exclusion of obstruction.
• Dose regimens: low dose start at 1 to 2 milliunits/min, increasing by 1 to 2 milliunits/min every 15 to 40 minutes; high dose start at 6 milliunits/min increasing by 3 to 6 milliunits/min every 15 to 40 minutes. Usual maximum 20 to 40 milliunits/min.
• The goal is 3 to 4 contractions per 10 minutes (more than 5 is tachysystole). Stop or reduce the infusion if tachysystole with fetal heart rate abnormality, and give terbutaline 0.25 mg subcutaneously if needed
• Reassess every 2 hours. If no progress after 4 hours of adequate contractions, proceed to caesarean section
• Caesarean section is indicated for cephalopelvic disproportion, arrest of dilation or descent, and fetal compromise

Second stage delay. Optimise maternal position, bladder emptying, oxytocin as needed, and provide encouragement.

Operative vaginal delivery (vacuum or forceps) if criteria are met:

• fully dilated
• ruptured membranes
• head engaged (station 0 or lower, not more than one fifth palpable abdominally)
• known position
• adequate analgesia
• empty bladder
• an operator with expertise

Abandon after three pulls, any detachment of cup, or failure of descent.

Caesarean otherwise, noting that a deeply impacted head needs the "push" method (vaginal disimpaction) or a reverse breech extraction.

Occipito posterior position. Many rotate spontaneously. If persistent: manual rotation at full dilation, rotational forceps or vacuum by experienced operators, or caesarean.

Breech presentation. External cephalic version at 36 weeks if no contraindication (tocolysis with terbutaline 0.25 mg SC), success about 40 to 60%. Planned caesarean at 39 weeks for persistent breech, or planned vaginal breech delivery in selected cases with an experienced operator.

Shoulder dystocia (HELPERR). Call for help, note the time. Evaluate for episiotomy. Legs: McRoberts manoeuvre (hyperflexion of hips) and suprapubic pressure (CPR hand position, continuous or rocking, directed to dislodge the anterior shoulder). If fails, internal manoeuvres: Rubin II (push on the posterior aspect of the anterior shoulder), Woods corkscrew, delivery of the posterior arm.

Then all-fours (Gaskin) or Zavanelli (cephalic replacement and caesarean) or symphysiotomy as last resorts. Avoid fundal pressure and excessive traction. Document the head-to-body interval and manoeuvres. Prepare for PPH and neonatal resuscitation.

Cord prolapse. Emergency. Elevate the presenting part off the cord by manual displacement or by filling the bladder (500 to 750 mL saline via Foley). Position in knee chest or exaggerated Sims with head down, and avoid handling the cord. Proceed to immediate caesarean section (category 1) or instrumental delivery if the cervix is fully dilated. Tocolysis (terbutaline 0.25 mg SC) can help while preparing.

Uterine rupture. Resuscitate, transfuse, emergency laparotomy; repair or hysterectomy depending on extent and desire for fertility.

Postpartum haemorrhage prevention. Routine active management of the third stage with oxytocin 10 IU IM. Treat atony with:

• Oxytocin infusion.
• Ergometrine 0.25 mg IM or IV (not in hypertension).
• Carboprost 250 micrograms IM every 15 minutes up to 8 doses (not in asthma).
• Misoprostol 800 micrograms sublingual or rectal.
• Tranexamic acid 1 g IV over 10 minutes (repeat after 30 minutes if bleeding continues).

Escalate to balloon tamponade, compression sutures, or hysterectomy.

Prevention. Antenatal identification of breech, macrosomia and previous caesarean; shared decision making for mode of birth; continuous labour support; partogram use; and avoiding unnecessary intervention before active labour.