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This is a clinician-written, evidence-based summary aligned to the 2026 MLA Content Map. It is intended for medical students and junior doctors preparing for the UKMLA. Always cross-reference with NICE guidance, local protocols, and clinical judgement.
Key points
- Commonest indication: prolonged pregnancy (≥41+0 weeks) — offer IOL from 41+0
- Other indications: PPROM at term, pre-eclampsia, GDM, IUGR, maternal request with medical reason
- Bishop score assesses cervical readiness: ≤5 = unfavourable (needs ripening), ≥6 = favourable (can consider amniotomy)
- Cervical ripening: vaginal dinoprostone (PGE₂) pessary or gel. Mechanical balloon catheter as alternative
- After cervical ripening: amniotomy + IV oxytocin infusion to establish contractions
- Continuous CTG required throughout oxytocin-augmented labour
Overview
Induction of labour (IOL) is the process of artificially initiating labour before spontaneous onset. It is one of the most common interventions in obstetrics, performed in approximately 30% of pregnancies in the UK. The decision to induce labour involves balancing the risks of continuing pregnancy against the risks of induction. IOL is associated with a higher rate of epidural use, instrumental delivery, and emergency caesarean section compared to spontaneous labour, and these risks should be discussed with women as part of shared decision-making.
Epidemiology
IOL is performed in approximately 30% of pregnancies in England. Prolonged pregnancy is the most common indication, accounting for approximately 30–40% of inductions. Other common indications include pre-eclampsia, gestational diabetes, fetal growth restriction, PPROM at term, and maternal request with medical justification. The rate of IOL has increased significantly over the past two decades.
Clinical Features
Symptoms
Post-dates pregnancy — no spontaneous labour by 41 weeks
Reduced fetal movements (if the indication is fetal concern)
Symptoms of the underlying condition prompting induction (e.g., headache in pre-eclampsia)
Signs
Bishop score assessment: cervical dilatation, effacement, consistency, position, and station of presenting part
Unfavourable cervix (Bishop score ≤5): requires cervical ripening before amniotomy
Favourable cervix (Bishop score ≥6): can proceed to amniotomy ± oxytocin
Investigations
First-line
Bishop scoreAssessed on vaginal examination. Scores position, consistency, effacement, dilatation of cervix + station of presenting part. Max score 13. ≥6 = favourable
CTGBaseline assessment of fetal wellbeing before starting induction
USSConfirm presentation, liquor volume, estimated fetal weight if clinically indicated
Second-line
FBC, group and saveBaseline bloods — particularly if pre-eclampsia or risk of haemorrhage
Specialist
USS cervical lengthMay predict likelihood of successful induction — shorter cervix generally more favourable
Management
NICE NG207 (Inducing labour), 20211
Membrane sweeping
- Offer at 40 weeks (nulliparous) and 41 weeks (multiparous)
- Sweeping the membranes from the lower uterine segment to release prostaglandins
- Reduces need for formal induction — offer before pharmacological methods
2
Cervical ripening (Bishop score ≤5)
- Vaginal dinoprostone (PGE₂): 10 mg controlled-release pessary (Propess) for 24 h, or 1–2 mg gel (repeat at 6 h, max 3 doses)
- Mechanical methods: Foley catheter or double-balloon catheter (Cook catheter) — inserted through cervix, inflated to dilate os
- Misoprostol (oral or vaginal) — used in some units as alternative to dinoprostone
- Reassess Bishop score after ripening — proceed to amniotomy if favourable
3
Amniotomy and oxytocin
- Amniotomy (ARM — artificial rupture of membranes): performed when cervix is favourable
- IV oxytocin (Syntocinon) infusion commenced if contractions do not establish within 2 h of amniotomy
- Start at low dose, titrate up every 30 min until 3–4 contractions in 10 min
- Continuous CTG required throughout oxytocin infusion
4
Failed induction
- If cervical ripening fails after 24 h: offer further ripening, mechanical methods, or discuss caesarean birth
- If in established labour but failing to progress: manage as failure to progress (augmentation or CS)
- Woman's preferences central to decision-making throughout
Complications
- Uterine hyperstimulation: >5 contractions in 10 min or contractions lasting >2 min — can cause fetal distress. Remove prostaglandin pessary, stop oxytocin, consider tocolysis (terbutaline 250 mcg SC)
- Uterine rupture: Rare but life-threatening — highest risk in women with previous CS undergoing prostaglandin induction
- Failed induction: May result in emergency CS
- Cord prolapse: Risk with amniotomy, especially if presenting part not engaged
- Increased intervention rate: IOL associated with higher rates of epidural, instrumental delivery, and CS compared to spontaneous labour
UKMLA Exam Tips
- 1Bishop score ≤5 = unfavourable cervix → needs ripening. ≥6 = favourable → can do amniotomy
- 2Dinoprostone (PGE₂) pessary or gel for cervical ripening — most commonly tested method
- 3IOL after previous CS: higher risk of uterine rupture with prostaglandins. Discuss mechanical methods or repeat CS
- 4Membrane sweep offered from 40 weeks (nulliparous) — a simple intervention that reduces need for formal IOL
- 5Hyperstimulation: >5 contractions/10 min. Remove pessary, stop oxytocin, tocolysis if needed
- 6IOL for prolonged pregnancy: offer from 41+0 weeks (NICE NG207)
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