Note: DC Dutta's Textbook of Obstetrics is not available in the medical library. The answer below is drawn from Creasy & Resnik's Maternal-Fetal Medicine (an authoritative obstetrics reference), and is supplemented with the standard content that DC Dutta covers on this topic from established knowledge. The core content is essentially the same.

Induction of Labour

Definition

Types

Indications

Maternal

• Pregnancy-induced hypertension / pre-eclampsia / eclampsia
• Chorioamnionitis
• Diabetes mellitus (uncontrolled)
• Severe Rh isoimmunization
• Chronic nephritis / renal disease
• Antepartum haemorrhage (select cases)
• Fetal death in utero (FDIU)

Fetal

• Post-term pregnancy (especially with oligohydramnios)
• Intrauterine growth restriction (IUGR) with evidence of fetal jeopardy
• Prelabour rupture of membranes (PROM) with established fetal maturity
• Isoimmunization (erythroblastosis fetalis)
• Hydramnios causing maternal distress
• Congenital anomaly incompatible with life

Contraindications

Absolute

• Placenta previa or vasa previa
• Cord presentation or cord prolapse
• Shoulder presentation / transverse lie
• Active genital herpes infection
• Previous classical (upper segment) uterine scar
• Pelvic structural deformity / contracted pelvis
• Invasive carcinoma of the cervix
• Acute severe fetal distress
• Uncontrolled haemorrhage

Relative

• Grand multiparity (parity ≥5)
• Multiple pregnancy
• Breech presentation
• Suspected cephalopelvic disproportion (CPD)
• Inability to adequately monitor fetal heart rate
• Previous lower segment caesarean section (LSCS) - requires careful evaluation

Prerequisites for Induction

1. Gestational age established (term or near-term)
2. Cephalic presentation confirmed
3. No CPD (clinically assessed pelvis)
4. Fetal wellbeing assessed (CTG, biophysical profile)
5. Cervical favourability assessed - Bishop Score
6. Informed consent obtained
7. Facilities for continuous fetal monitoring available
8. Caesarean section backup available

Bishop Score (Pelvic Scoring for Elective Induction)

• Score ≥8: Favourable cervix - induction likely to succeed; amniotomy alone may suffice
• Score 6-7: Moderately favourable - proceed with caution; cervical ripening may help
• Score ≤5: Unfavourable cervix - cervical ripening required before induction
• Bishop found that a score ≥9 in multiparous women was associated with no failed inductions and average labour of 4 hours
• A score ≤5 in nulliparous women carries a 50% risk of failed induction
• Dilation is the single most important component of the Bishop score

Methods of Cervical Ripening

1. Mechanical Methods

• Balloon catheter (Foley): A 14-16 Fr Foley catheter is inserted through the internal os and the balloon inflated with 30-60 mL saline; exerts mechanical pressure on the cervix. Comparable to misoprostol for ripening; less likely to cause hyperstimulation.
• Laminaria tents: Dried seaweed (or synthetic) hygroscopic dilators placed in cervical canal; expand gradually over hours.
• Extra-amniotic saline infusion (EASI): Saline infused through Foley catheter beyond the internal os.

2. Pharmacological Methods

Prostaglandins (PGE2 - Dinoprostone)

• Intravaginal gel: 1-2 mg PGE2 in posterior fornix; repeat after 6 hours if needed
• Intracervical gel: 0.5 mg dinoprostone gel placed into cervical canal
• Controlled-release pessary: 10 mg dinoprostone (Cervidil) over 12-24 hours; advantage of removal if hyperstimulation occurs
• More effective than oxytocin alone for ripening an unfavourable cervix

Misoprostol (PGE1 - Cytotec)

• 25-50 µg vaginally every 4-6 hours (25 µg preferred to reduce hyperstimulation risk)
• Can also be given orally or sublingually
• More effective and cheaper than PGE2
• Meta-analyses confirm misoprostol is superior to intravaginal/intracervical PGE2 for ripening and induction
• Caution: Risk of uterine tachysystole/hyperstimulation; avoid in previous uterine scar at ≥28 weeks

3. Membrane Sweeping (Stripping)

• Digital separation of fetal membranes from lower uterine segment during vaginal examination
• Releases local prostaglandins; increases likelihood of spontaneous labour onset within 48 hours
• Considered a preliminary step rather than formal induction

Methods of Induction of Labour

1. Amniotomy (Artificial Rupture of Membranes - ARM)

• Surgical rupture of fetal membranes using an amnihook or Kocher's forceps
• Preferred when: Bishop score ≥8, vertex well engaged, cervix favourable
• Allows fetal head to descend and apply direct pressure on cervix
• Prostaglandin release from decidua augments contractions
• Usually followed by oxytocin infusion within 1-2 hours if labour does not establish
• Risks: cord prolapse (if head not engaged), ascending infection, fetal heart rate decelerations

2. Oxytocin Infusion

• Synthetic oxytocin (Syntocinon) given IV via infusion pump - never as a bolus
• Usually combined with ARM for effective induction
• Low-dose regimen: Start at 1-2 mU/min; increase by 1-2 mU/min every 30-60 minutes
• High-dose regimen: Start at 6 mU/min; increase by 6 mU/min every 15-40 minutes
• Target: 3-5 contractions per 10 minutes, each lasting 40-60 seconds
• Maximum dose: typically 20-40 mU/min (varies by protocol)
• Continuous CTG monitoring is mandatory during oxytocin infusion
• Complications: uterine hyperstimulation, fetal distress, water intoxication (with high doses in large volumes)

3. Combination (ARM + Oxytocin)

• Standard protocol when cervix is favourable: ARM first, then oxytocin if contractions don't establish within 1-2 hours
• Most effective method overall

Cervical Ripening Mechanism

• Cytokine production (TNF-α, IL-1β, IL-6, IL-8)
• Neutrophil extravasation into cervical stroma
• Protease release that degrades cross-linked collagen
• Increased water content and glycosaminoglycans
• Smooth muscle cell apoptosis
• Net result: softening, effacement, and early dilation

Failed Induction

• Adequate cervical ripening, AND
• Oxytocin for ≥12-18 hours after ARM (or ≥24 hours without ARM)

• Continue oxytocin for longer (if mother and fetus stable)
• Caesarean section

Complications of Induction

Special Considerations

Previous LSCS

• Misoprostol is contraindicated at ≥28 weeks (risk of scar rupture)
• At <28 weeks: standard misoprostol dosing may be used
• At ≥28 weeks: oxytocin + Foley balloon catheter is the preferred approach
• Classical scar: repeat CS is appropriate

Post-term Pregnancy (>42 weeks)

• Induction is indicated due to rising perinatal mortality
• Assess cervix; ripen if necessary
• IOL at 41-42 weeks is associated with lower perinatal mortality without increasing CS rates (ARRIVE trial data)

PROM at Term

• Induction with oxytocin within 12-24 hours recommended to reduce infection risk
• GBS prophylaxis as indicated

Key Points (DC Dutta Style Summary)

1. IOL is indicated when continuation of pregnancy is more hazardous than delivery
2. Bishop score is the cornerstone of pre-induction assessment; score <6 requires cervical ripening
3. Amniotomy + oxytocin is the standard method when cervix is favourable
4. Misoprostol (25 µg vaginally every 4-6 h) is the most effective cervical ripening agent
5. Continuous fetal monitoring is mandatory throughout induction
6. Absolute contraindications must be excluded before any induction attempt
7. Failed induction (10-15%) requires careful reassessment and usually ends in CS