Preparatory Mindset
Labour is the endpoint of pregnancy — and the chapter where the physiology of ch01 pays off. The exam mindset: master the three definitions (engagement, station, Bishop score), the four stages of labour, the partograph, and the three "P"s (powers, passenger, passage). The most tested concepts:
- Diagnosis of labour: regular painful contractions + cervical dilatation ≥3 cm + effacement (with rupture of membranes).
- Normal progress: 1st stage dilates ~1 cm/h (primip) / ~1.2-1.5 cm/h (multip); 2nd stage ≤2 h (primip) / ≤1 h (multip).
- The partograph plots cervical dilatation vs time with an action line — crossing it = abnormal progress → intervention.
- Cardinal movements of labour (mechanism): engagement → descent → flexion → internal rotation → extension → external rotation (restitution) → expulsion.
- Abnormal labour (dystocia): prolonged latent phase, protracted/arrested active phase (→ oxytocin, C-section), malpresentation (breech, transverse), fetal distress (→ urgent delivery), shoulder dystocia (manoeuvres).
The priority in abnormal labour: recognise slow progress early, correct the cause, avoid obstructed labour and its sequelae (uterine rupture, vesicovaginal fistula, fetal death).
Core Concepts
1. Definitions and prelabour
- Engagement: fetal presenting part at or below the pelvic inlet (station 0 = ischial spines).
- Presentation: vertex (most common), breech, face, brow, shoulder (transverse lie).
- Position: occipito-anterior (OA, most favourable) > occipito-posterior (OP, longer labour) > occipito-transverse (OT).
- Bishop score — predicts induction success (0-13):
| Parameter | 0 | 1 | 2 | 3 |
|---|---|---|---|---|
| Dilatation (cm) | 0 | 1-2 | 3-4 | ≥5 |
| Effacement (%) | 0-30 | 40-50 | 60-70 | ≥80 |
| Station | −3 | −2 | −1/0 | +1/+2 |
| Consistency | Firm | Medium | Soft | — |
| Position | Posterior | Mid | Anterior | — |
Score ≥6-8 → favourable for induction.
2. Four stages of labour
| Stage | Definition | Normal duration |
|---|---|---|
| 1st stage | Onset of labour → full dilatation (10 cm); latent (slow, <3-4 cm) + active (≥3-4 cm, ~1 cm/h) | Primip ~8-12 h; multip ~5-8 h |
| 2nd stage | Full dilatation → delivery of baby; active pushing; descent + rotation + expulsion | Primip ≤2 h (≤3 h with epidural); multip ≤1 h |
| 3rd stage | Delivery of baby → delivery of placenta (separation + expulsion) | ~5-15 min (up to 30) |
| 4th stage | First 1-2 h postpartum — observation for PPH (the danger window) | 1-2 h |
Partograph essentials: plot cervical dilatation (X: time, Y: cm), descent of presenting part, contraction frequency, fetal heart, amniotic fluid, BP/pulse/temp/urine. Alert line (normal progress) and action line (4 h later) — crossing action line → review + intervene (oxytocin for hypotonic uterine action if no obstruction).
3. Mechanism of labour (vertex, OA)
- Engagement (biparietal diameter passes inlet)
- Descent (continuous, driven by contractions + bearing down)
- Flexion (resistance → fetal chin to chest, smallest diameter presents)
- Internal rotation (occiput rotates from transverse/oblique to anterior)
- Extension (delivery of head — occiput anterior, chin clears perineum)
- External rotation (restitution) — shoulders rotate
- Expulsion — anterior shoulder then posterior shoulder delivered
4. First stage management
- Monitor: contractions, FHR (intermittent auscultation or CTG), cervical dilatation (VE q4 h in active), maternal vitals/urine.
- Pain relief: non-pharmacological (birthing ball, water), pethidine, epidural analgesia, nitrous oxide, TENS.
- Comfort: mobility, fluids, low-risk → ambulatory.
- Rupture of membranes: note time/colour (meconium = fetal distress consideration), monitor.
5. Second stage management
- Pushing with contractions (coached vs spontaneous); upright positions may help.
- FHR monitoring every 5 min (intermittent) or continuous CTG.
- Delayed pushing if epidural (passive descent).
- Episiotomy: restrictive (not routine) — for fetal distress, shoulder dystocia, instrumental delivery.
- Assisted vaginal delivery (ventouse/forceps) for prolonged 2nd stage, fetal distress, maternal exhaustion/medical indication (e.g., cardiac disease, myasthenia).
- Perineal tears — grade I-IV; repair; 3rd/4th degree (anal sphincter involvement) — specialist repair + postpartum follow-up (fistula/incontinence risk).
6. Abnormal labour (dystocia)
| Abnormality | Definition | Management |
|---|---|---|
| Prolonged latent phase | Latent >20 h (primip) / >14 h (multip) | Rest, analgesia, review; may be false labour |
| Protracted active phase | Dilatation <1 cm/h over 4 h | Assess: inadequate contractions (→ oxytocin), obstruction, malposition |
| Arrest of active phase | No dilatation for ≥4 h (primip) / ≥2 h (multip) with adequate contractions; or ≥6 h with inadequate | C-section (especially with obstruction); trial of oxytocin if no obstruction |
| Prolonged 2nd stage | Pushing >2 h (primip) / >1 h (multip) | Assisted vaginal delivery or C-section |
| Obstructed labour | Absolute cephalopelvic disproportion; retraction ring (Bandl), oedematous cervix, caput/moulding, fetal distress, maternal exhaustion | Immediate C-section (avoid prolonged obstructed labour → rupture, fistula) |
| Uterine hyperstimulation | >5 contractions/10 min (oxytocin) | Stop oxytocin, tocolysis if fetal distress |
7. Malpresentation
| Type | Key points |
|---|---|
| Breech | Frank (legs flexed at hips) — most common; footling (cord prolapse risk). External cephalic version (ECV) at 36-37 wk if eligible; planned C-section common (or assisted vaginal breech in select experienced centres); footling breech → C-section |
| Face / brow | Rare; brow → spontaneous conversion or C-section; mento-anterior face may deliver vaginally |
| Transverse lie / shoulder | C-section; cord prolapse + obstructed labour risk |
| Occipito-posterior | Longer labour, more back pain; try rotation (position change); often delivers OP or rotates; instrumental/C-section if arrest |
8. Shoulder dystocia — the emergency
Risk: GDM/macrosomia, previous shoulder dystocia, prolonged 2nd stage, assisted delivery.
Signs: head delivers, chin retracts, turtle sign (head retracts against perineum) — do not pull!
Manoeuvres (HELPERR):
- Help — call for help, McRoberts (hyperflex thighs on abdomen), suprapubic pressure
- Evaluate for episiotomy
- Legs — McRoberts position maintained
- Pelvic manoeuvres — rotate (Rubin: push on posterior shoulder; Woods screw)
- Enter — deliver posterior arm (flex at elbow, sweep out)
- Roll — all-fours / Gaskin manoeuvre
- Repeat / remove — symphysiotomy or Zavanelli (last resort)
Complications: brachial plexus injury (Erb palsy — C5-6), clavicle/humerus fracture, fetal hypoxia/death, maternal PPH/perineal trauma.
High-Yield Points
| Topic | Must-remember |
|---|---|
| Labour diagnosis | Regular contractions + cervical dilatation ≥3 cm + effacement |
| 4 stages | 1st (→10 cm), 2nd (→birth), 3rd (→placenta), 4th (PPH watch) |
| Bishop score | ≥6-8 = favourable induction |
| Cardinal movements | Engagement → descent → flexion → internal rotation → extension → external rotation → expulsion |
| Action line | Crossed → review + intervene (oxytocin / C-section) |
| Arrest of active phase | No dilatation ≥4 h → C-section (if obstruction) |
| Obstructed labour | Immediate C-section — avoid rupture/fistula |
| Breech | Frank most common; ECV 36-37 wk; footling → C-section |
| Shoulder dystocia | McRoberts + suprapubic pressure first; never pull head |
| Erb palsy | C5-6 brachial plexus — shoulder dystocia |
| Episiotomy | Restrictive |
| 3rd degree tear | Anal sphincter — specialist repair |
Topic Summary
Labour is a four-stage process driven by powers (contractions), passenger (fetus), passage (pelvis). Normal progress is tracked on the partograph (cervical dilatation vs time, alert/action lines). The cardinal movements deliver the vertex presentation. Dystocia — prolonged/arrested progress — is managed by reassessment (oxytocin for hypotonic uterus, C-section for obstruction). Malpresentation (breech, transverse) usually means planned C-section. Shoulder dystocia is the acute emergency: McRoberts + suprapubic pressure, never traction on the head. The 4th stage (PPH watch) bridges directly to the next chapter.
LMCHK OSCE Practice — Prolonged First Stage
Station setup: A 24-year-old primigravida at term, in labour 14 hours. Contractions now 3 in 10 min, moderate. VE: cervix 5 cm, 60% effaced, station −1, intact membranes. FHR 150 with good variability. She is exhausted and requesting an epidural.
Candidate tasks (8 min):
- Assess the progress — 14 h, 5 cm: likely in active phase; plot on partograph; compare to alert/action line (is progress adequate?).
- Order review of contractions + fetal monitoring (CTG) + re-VE in 2-4 h.
- If protracted active phase (crossing action line with adequate contractions) → reassess for obstruction; if no obstruction → oxytocin augmentation; if arrest + obstruction → C-section.
- Provide analgesia (epidural) and support; check maternal vitals, urine output, temperature (chorioamnionitis?).
- Explain the plan to the patient in plain language.
Key marking cues:
- Uses the partograph to judge progress objectively.
- Distinguishes protracted vs arrested labour and acts accordingly (oxytocin vs C-section).
- Monitors for fetal distress and chorioamnionitis.
- Supports the woman (analgesia, fluids, explanation) — communication matters in OSCE.
- Knows the action line concept.