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Induction and Augmentation of Labour

Definitions

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Indications for Induction

Absolute / Compelling

• Post-term pregnancy (≥41–42 weeks)
• Pre-eclampsia / eclampsia
• Premature rupture of membranes (PROM) at term
• Chorioamnionitis
• Placental abruption (stable)
• Fetal compromise (growth restriction with abnormal Doppler, oligohydramnios)
• Isoimmunisation (e.g. Rh disease)
• Maternal medical conditions: uncontrolled diabetes, renal disease, antiphospholipid syndrome

Elective / Relative

• Social / logistical (limited evidence of benefit; requires careful counselling)
• Previous rapid labour with risk of unattended birth

Contraindications

• Placenta praevia or vasa praevia
• Transverse/oblique lie
• Active genital herpes
• Prior classical uterine incision
• Cord prolapse
• Pelvic structural abnormality

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Bishop Score — Cervical Assessment

• Score ≥8: favourable; induction likely to succeed without prior ripening
• Score ≤6: unfavourable; cervical ripening recommended first
• Score <5: low success rate if oxytocin used alone

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Cervical Ripening Methods

Pharmacological

Mechanical

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Induction Methods

Oxytocin (Syntocinon)

• Low-dose: Start 1–2 mU/min; increase by 1–2 mU/min every 30–40 min
• High-dose: Start 6 mU/min; increase by 6 mU/min every 15 min
• Maximum: typically 20–40 mU/min

• Continuous CTG (cardiotocography)
• Frequency: aim for 3–5 contractions per 10 minutes
• Reduce/stop if tachysystole (>5 contractions/10 min) or fetal heart rate abnormalities

• Uterine tachysystole / hyperstimulation
• Fetal distress (non-reassuring CTG)
• Water intoxication / hyponatraemia (antidiuretic effect at high doses)
• Uterine rupture (especially with scarred uterus)

Amniotomy (ARM)

• Performed when cervix is ≥2–3 cm dilated and presenting part is engaged
• Accelerates labour by enhancing prostaglandin release and direct pressure
• Usually combined with oxytocin if contractions do not establish within 1–2 hours

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Augmentation of Labour

Assessment before augmentation

• Confirm no obstruction (exclude CPD — cephalopelvic disproportion)
• Assess fetal wellbeing
• Assess partogram progress

Methods

1. Amniotomy — first step if membranes intact
2. Oxytocin infusion — as above; titrate to achieve adequate contractions
3. Combination of both

The Partogram

• Alert line: cervical dilation expected at ≥1 cm/hour in active phase
• Action line: 2–4 hours to the right of the alert line; crossing indicates need for intervention

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Special Considerations

Induction with a Uterine Scar (Previous Caesarean)

• Prostaglandins (especially misoprostol) are relatively contraindicated — ↑ uterine rupture risk
• Mechanical methods (balloon catheter) and oxytocin are preferred
• Requires continuous fetal monitoring and low threshold for caesarean

Pre-labour Rupture of Membranes (PROM) at Term

• Induce within 12–24 hours to reduce infection risk (chorioamnionitis, neonatal GBS sepsis)
• Oxytocin preferred over expectant management in most guidelines

Post-term Pregnancy (>41 weeks)

• Induction reduces perinatal mortality vs expectant management
• Bishop score guides method selection
• Most guidelines recommend induction by 41–42 weeks

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Complications of Induction/Augmentation

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Summary Algorithm

Assess indication → Check Bishop score
        ↓
Score ≥8           Score <8
   ↓                    ↓
Direct           Cervical ripening
induction        (PGE₂, misoprostol, or balloon)
   ↓                    ↓
Amniotomy + Oxytocin infusion
        ↓
Monitor with CTG + Partogram
        ↓
Progress adequate → Continue
Progress inadequate → Augment (ARM + Oxytocin)
        ↓
CPD / Fetal distress → Caesarean section

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Premature Rupture of Membranes (PROM)

Based on Creasy & Resnik's Maternal-Fetal Medicine + Williams Obstetrics Chapter 27 Framework

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Definitions

At term (~8% of pregnancies), labour usually begins within 24 hours of PROM. Preterm PROM (~3% of pregnancies) accounts for ~30–40% of all preterm births and is a leading cause of perinatal morbidity and mortality.

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Anatomy of the Fetal Membranes

• Amnion: inner layer — single cuboidal epithelium with compact and spongy connective tissue layers
• Chorion: outer, thicker layer — reticular and trophoblastic layers adhering to maternal decidua

• Changes in collagen content and type
• Alterations in the intercellular matrix
• Progressive cellular apoptosis

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Pathophysiology

Physiologic (Term) PROM

• Matrix metalloproteinases (MMPs) — thrombin-mediated activation
• Decreased Tissue Inhibitors of MMPs (TIMPs)
• Increased poly(ADP-ribose) polymerase cleavage
• Uterine contractions increasing intraamniotic pressure

Pathologic (Preterm) PROM — Multiple Pathways

Associated Pathogens

• Neisseria gonorrhoeae
• Chlamydia trachomatis
• Trichomonas vaginalis
• Group B β-haemolytic Streptococcus (GBS)
• Bacterial vaginosis organisms

Amniotic fluid cultures after PROM are positive in 25–35% of cases. Histological evidence of acute chorioamnionitis is frequently found at preterm birth following PROM.

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Risk Factors

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Diagnosis

Clinical Presentation

• History: gush or continuous leakage of fluid per vagina (often unmistakable)
• Distinguish from: urinary incontinence, increased vaginal discharge, show

Examination

• Sterile speculum exam (avoid digital vaginal examination — ↑ infection risk and ↓ latency)
  • Pooling of fluid in the posterior fornix
  • Fluid flowing from the cervical os (Valsalva / coughing)

Bedside / Laboratory Tests

False positives with nitrazine: blood, semen, vaginal infection, alkaline urine. False positives with ferning: cervical mucus (but pattern is coarser).

Ultrasound

• Oligohydramnios supports the diagnosis (AFI <5 cm or single pocket <2 cm)
• Normal fluid does NOT exclude PROM
• Assesses gestational age, presentation, placental location, fetal wellbeing

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Complications

Maternal

Fetal / Neonatal

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Management

Decision Framework by Gestational Age

PROM confirmed
      ↓
Assess: GA, fetal wellbeing, signs of infection/abruption/labour
      ↓
≥37 weeks (Term PROM) ──────────────→ Induce if not in spontaneous labour
                                        within 12–24 hours
24–36+6 weeks (Preterm PROM) ───────→ Gestational age-dependent management
<24 weeks (Periviable PROM) ─────────→ Counselling re: prognosis; conservative
                                        or palliative approach

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Term PROM (≥37 weeks)

• Spontaneous labour within 24 hours in the majority
• If no spontaneous labour: induction with oxytocin (preferred) is as effective as expectant management and reduces chorioamnionitis risk
• GBS prophylaxis: if GBS status unknown, treat as positive
• Vaginal delivery is the goal; caesarean for standard obstetric indications

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Preterm PROM — Conservative (Expectant) Management

Key Interventions

Monitoring During Conservative Management

• Daily: temperature, pulse, fetal HR, uterine tenderness, vaginal discharge
• Regular: FBC, CRP (markers of infection)
• CTG: at least daily
• Ultrasound: AFI, fetal growth, Doppler, biophysical profile

Markers of Chorioamnionitis

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Gestational Age–Specific Management

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Delivery Indications During Conservative Management

• Absolute: chorioamnionitis, placental abruption with haemorrhage, non-reassuring fetal status
• Relative: gestational age reached (per local protocol, usually 34 weeks), labour established

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Antibiotic Regimen (Detail — Williams/ACOG Protocol)

• IV phase (48h): Ampicillin 2 g IV q6h + Erythromycin 250 mg IV q6h
• Oral phase (5 days): Amoxicillin 250 mg PO q8h + Erythromycin base 333 mg PO q8h

Do NOT use amoxicillin-clavulanate — Oracle trial showed ↑ neonatal NEC.

• Azithromycin, clarithromycin are acceptable alternatives

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PROM Before Viability (<23 weeks)

• Survival and intact neurological outcome are significantly reduced
• Detailed counselling with neonatology essential
• Some cases involve resealing of membranes (~2–15%)

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Summary of Key Points (Williams Ch. 27 Framework)

1. PROM complicates ~8% of term and ~3% of all pregnancies; PPROM causes ~30% of preterm births
2. Ascending infection is the primary pathophysiology of preterm PROM
3. Diagnosis: sterile speculum + ferning + nitrazine ± PAMG-1/IGFBP-1; avoid digital exam
4. Term PROM: deliver within 12–24 hours — oxytocin induction preferred
5. Preterm PROM: conservative management with corticosteroids + latency antibiotics + MgSO₄ (if <32 wks)
6. Deliver promptly for chorioamnionitis, abruption, non-reassuring fetal status regardless of GA
7. GBS prophylaxis is mandatory intrapartum
8. Tocolysis is NOT routinely indicated after PROM
9. Periviable PROM requires multidisciplinary counselling regarding prognosis

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Preterm Labour

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Definition

Preterm birth (delivery <37 weeks) complicates ~10–12% of all pregnancies and is the leading cause of neonatal morbidity and mortality worldwide.

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Classification by Aetiology

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Pathophysiology

1. Intrauterine Infection / Inflammation

• Ascending bacteria activate the decidua and membranes → release of cytokines (IL-1β, IL-6, TNF-α) and prostaglandins (PGE₂, PGF₂α)
• Prostaglandins stimulate uterine contractions and cervical ripening
• Pathogens: Ureaplasma urealyticum, Mycoplasma hominis, GBS, anaerobes
• Amniotic fluid cultures positive in 25–35% of PPROM; subclinical infection present in up to 15% of women with intact membranes and PTL

2. Uteroplacental Ischaemia / Decidual Haemorrhage

• Abruption → thrombin generation → uterotonic effect
• Placental insufficiency / IUGR → early parturition signal

3. Uterine Overdistension

• Multiple gestation, polyhydramnios → mechanical stretch → ↑ gap junctions, oxytocin receptors, contraction-associated proteins (CAPs)

4. Cervical Insufficiency

• Structural weakness → painless, progressive cervical dilatation
• Congenital (collagen disorders) or acquired (prior trauma, LLETZ)

5. Stress / Neuroendocrine Activation

• Maternal or fetal stress → ↑ CRH (placental) → activates fetal HPA axis → ↑ cortisol and DHEAS → ↑ oestrogen:progesterone ratio → parturition

6. Progesterone Withdrawal (Functional)

• Progesterone maintains uterine quiescence by suppressing CAPs
• Functional progesterone withdrawal (receptor changes) initiates parturition

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Risk Factors

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Diagnosis

Traditional Clinical Criteria

• Regular uterine contractions ≥4 in 20 minutes or ≥8 in 60 minutes
• Plus cervical change: dilatation ≥2 cm OR effacement ≥80%

Diagnosis is challenging — 40–70% of women diagnosed clinically are NOT in true preterm labour. Overdiagnosis leads to unnecessary treatment.

Symptoms

• Pelvic pressure or heaviness
• Low back pain (constant or crampy)
• Menstrual-like cramps
• Increased or changed vaginal discharge
• Abdominal tightening or contractions
• Signs of PPROM (fluid leakage)

Symptoms suggest PTL more by persistence than by severity. Contractions against an uneffaced cervix are often painful; contractions against an effacing cervix may be felt only as pressure.

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Diagnostic Tests

1. Transvaginal Ultrasound (TVU) Cervical Length

• Transabdominal measurement is unreliable — always use TVU
• High negative predictive value (NPV ~96%) — most useful for ruling out imminent delivery

2. Fetal Fibronectin (fFN)

• Fetal fibronectin: glycoprotein at the decidua–chorion interface; normally absent from cervicovaginal secretions between 22–34 weeks
• Positive: ≥50 ng/mL → ↑ risk of delivery within 7–14 days
• Negative result is most clinically valuable: NPV ~99.5% for delivery within 7 days
• Must be collected before digital exam or intercourse (false positives)
• Do not collect if membranes ruptured or if cervix is ≥3 cm dilated

Combined Algorithm (Cervical Length + fFN)

Symptoms of PTL + cervix <3 cm dilated
              ↓
        TVU Cervical Length
       /          |          \
   ≥30 mm     15–29 mm     <15 mm
      ↓            ↓           ↓
  Reassure     Measure fFN  High risk
  Discharge    /      \      → Admit
            Neg    Pos    → Treat
           Discharge  Admit + treat

A short cervix alone (<15–20 mm) or short cervix + positive fFN identifies the highest-risk group. Protocols using both tests have high NPV and improve appropriate use of antenatal corticosteroids.

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Prevention of Preterm Birth

Primary Prevention (Risk Reduction)

Secondary Prevention (High-Risk Women — Prior PTB or Short Cervix)

Progesterone

Neither formulation is effective in multiple gestations. A large 2019 trial (PROLONG) questioned the efficacy of 17-OHPC in an unselected population, though it remains recommended in guidelines for those with prior spontaneous PTB.

Cervical Cerclage

1. History-indicated (elective): Prior painless mid-trimester loss or classic cervical incompetence — placed at 12–14 weeks
2. Ultrasound-indicated: Short cervix <25 mm before 24 weeks in a woman with prior spontaneous PTB
3. Emergency (rescue) cerclage: Cervical dilatation 1–4 cm with bulging membranes, before 24 weeks

Arabin Pessary

• Silicone device placed around cervix to redirect uterine forces
• Some studies show benefit in singleton with short cervix; conflicting evidence in twins

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Management of Acute Preterm Labour

Initial Assessment

1. Confirm gestational age (ultrasound)
2. Confirm diagnosis (contractions + cervical change)
3. Assess fetal wellbeing (CTG, biophysical profile)
4. Exclude: PPROM, chorioamnionitis, abruption, placenta praevia
5. Assess cervical length by TVU and/or fFN
6. GBS swab (if not done)

Hospitalisation

• Women in confirmed PTL <34 weeks should be hospitalised
• Transfer to tertiary centre (level III/IV) ideally before delivery if <32–34 weeks

1. Antenatal Corticosteroids (ACS) — MOST IMPORTANT INTERVENTION

• Late preterm (34–36+6 wks): Betamethasone single course reduces RDS, TTN, surfactant use, NICU admission — recommended if not previously given
• A single rescue course may be given if prior course >14 days ago and still <34 weeks

• ↓ Neonatal death
• ↓ Respiratory distress syndrome (RDS)
• ↓ Intraventricular haemorrhage (IVH)
• ↓ Patent ductus arteriosus (PDA)
• ↓ Necrotising enterocolitis (NEC)

2. Tocolysis

• Allow ACS to take effect (48 hours needed for maximal benefit)
• Facilitate maternal transfer to tertiary centre

Tocolysis does NOT improve neonatal outcomes directly and does not change the ultimate gestational age at delivery. It buys time.

• Confirmed PTL at 24–34 weeks
• No contraindications (see below)

• Chorioamnionitis
• Severe pre-eclampsia / eclampsia
• Non-reassuring fetal status
• Placental abruption with haemodynamic compromise
• Fetal lethal anomaly or demise
• Advanced cervical dilatation (>4–5 cm)

Tocolytic Agents

3. Magnesium Sulfate for Neuroprotection

• Given when delivery anticipated at <32 weeks
• Regimen: 6 g IV bolus over 20–30 min, then 2 g/h infusion for up to 12 hours
• Benefit: Reduces moderate-to-severe cerebral palsy (1.9% vs 3.9%, NNT ~63), reduces IVH, PVL, and neurodevelopmental delay
• Monitor for toxicity: respiratory rate, reflexes, urine output; antidote = 10 mL of 10% calcium gluconate IV

4. GBS Prophylaxis

• Intrapartum prophylaxis: Penicillin G 5 MU IV then 2.5 MU q4h; or ampicillin 2 g then 1 g q4h
• Indicated if GBS status unknown or positive at <37 weeks

5. Antibiotics

• NOT routinely indicated for PTL with intact membranes — do not prolong pregnancy or improve neonatal outcome (may be harmful; Oracel trial)
• ARE indicated in PPROM (latency antibiotics)
• Treat specific infections if identified (BV, UTI)

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Regionalised Care

Transfer to a Level III/IV centre before delivery is strongly associated with improved outcomes for infants born <32 weeks. This is the most important organisational intervention.

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Neonatal Complications of Prematurity

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Summary Algorithm

Threatened PTL (contractions ± cervical change, 24–36+6 wks)
                    ↓
     Confirm GA, exclude PPROM/infection/abruption
                    ↓
         TVU cervical length ± fFN
                    ↓
      High risk (short CL / +ve fFN)?
           YES                  NO
            ↓                    ↓
     Admit to Level III     Discharge + review
            ↓
   Antenatal corticosteroids (23–34 wks)
            ↓
   MgSO₄ neuroprotection (<32 wks)
            ↓
   Tocolysis (to allow ACS / transfer)
            ↓
   GBS prophylaxis if delivery likely
            ↓
   Monitor: CTG, temperature, WBC, CRP
            ↓
   Deliver for: chorioamnionitis, fetal compromise,
               advanced labour, or planned GA

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