What is the recommended protocol for inducing labour at ≥37 weeks in a singleton, cephalic pregnancy without maternal or fetal contraindications, including cervical ripening, oxytocin infusion, and management of complications?

Labor Induction Protocol at ≥37 Weeks for Singleton Cephalic Pregnancy

Initial Cervical Assessment

Begin by assessing the Bishop score to determine cervical favorability; this single measurement dictates your entire induction strategy. 1

• Bishop score <5 (unfavorable cervix): Cervical ripening is mandatory before oxytocin will be effective 2, 1
• Bishop score ≥5 (favorable cervix): Proceed directly to oxytocin infusion and/or artificial rupture of membranes 1

Cervical Ripening for Unfavorable Cervix (Bishop <5)

First-Line Agent Selection

For most patients with an unfavorable cervix, use either dinoprostone gel or oral misoprostol as your cervical ripening agent. 2, 1

Dinoprostone (Prostaglandin E₂) Protocol

• Dosing: Single 10 mg vaginal insert releasing 0.3 mg/hour 2, 1
• Duration: Remove after 12 hours maximum or upon onset of active labor, whichever comes first 2
• Monitoring: Continuous fetal heart rate and uterine activity monitoring throughout administration 2, 1
• Timing before oxytocin: Wait at least 30 minutes after removing the insert before starting oxytocin 2, 1

Oral Misoprostol Alternative

• Dosing: 20-25 µg every 2-6 hours 2, 1
• Advantages: Results in fewer cesarean sections (RR 0.84) and costs significantly less than dinoprostone 2, 1
• Critical contraindication: Absolutely contraindicated in women with prior cesarean delivery due to approximately 13% uterine rupture risk 1

Absolute Contraindications to Prostaglandins

Screen every patient for these contraindications before administering any prostaglandin agent:

• Active cardiovascular disease: Dinoprostone causes marked blood pressure changes, potential coronary vasospasm, and arrhythmia risk 2, 1
• Cyanotic heart disease: Dinoprostone reduces systemic vascular resistance and worsens hemodynamics 2
• Prior uterine surgery (for misoprostol only): Use dinoprostone or mechanical methods instead 1

Mechanical Cervical Ripening (Foley Catheter)

In women with active cardiovascular disease, cyanotic conditions, or prior cesarean delivery, use mechanical cervical ripening (Foley catheter) as the preferred method. 2, 1

• This approach avoids systemic hemodynamic effects while achieving effective cervical change 2, 1
• Mechanical methods are equally effective and safer in high-risk cardiac patients 2, 1

Oxytocin Augmentation Protocol

After completing cervical ripening (or if Bishop score ≥5 initially), begin oxytocin infusion with careful titration. 1, 3

Oxytocin Safety Considerations

• Proper dosing and careful fetal/maternal monitoring prevent complications including uterine hypercontractility with fetal distress, uterine rupture, maternal hypotension, and water intoxication 3
• Continuous fetal heart rate monitoring is mandatory throughout oxytocin administration 3
• Titrate oxytocin to achieve adequate uterine contractility without hyperstimulation 3

Amniotomy (Artificial Rupture of Membranes)

Reserve amniotomy as an adjunctive measure rather than a primary induction method. 1

• Amniotomy is most effective when combined with oxytocin in women with favorable cervix 1
• Do not perform amniotomy alone as the sole induction method 1

Defining Failed Induction

Critical Time Threshold

Allow at least 12 hours after completion of cervical ripening, membrane rupture, and oxytocin infusion before declaring "failed induction" and proceeding to cesarean delivery. 1

• This 12-hour minimum observation period lowers cesarean rates without harming maternal or neonatal outcomes 1
• Nulliparous women require longer induction times (often 24+ hours total) 1
• Multiparous women progress faster with dilation rates ≥1.5 cm/hour 1

Common Causes of Failed Induction

Evaluate these factors when induction stalls:

• Cephalopelvic disproportion (CPD): Accounts for 25-30% of protracted labor; assess maternal obesity, diabetes, and suspected macrosomia as risk factors 1
• Fetal malposition: Occiput posterior or transverse positions predict prolonged labor and potential failure 1
• Inadequate uterine contractility: Difficult to diagnose; current monitoring cannot reliably differentiate adequate from inadequate patterns 1
• Iatrogenic factors: High-level neuraxial analgesia can suppress cervical change and slow progress 1

Management of Complications

Hypertensive Emergencies During Labor

If blood pressure ≥160/110 mmHg lasting >15 minutes, initiate immediate drug treatment. 4

First-Line Antihypertensive Agents

• Intravenous labetalol: 10-20 mg initial dose, then 20-80 mg every 10-30 minutes (maximum 300 mg) 4
• Oral nifedipine (immediate-release): 10-20 mg, repeat in 30 minutes if needed 4
  • Caution: Avoid combining with magnesium sulfate due to risk of uncontrolled hypotension and fetal compromise 4

Agents to Avoid

• Intravenous hydralazine: Associated with greater risk of cesarean section, placental abruption, maternal oliguria, and fetal tachycardia; requires close monitoring 4
• Methyldopa: Should not be used for urgent blood pressure reduction 4

Eclampsia Prevention

Magnesium sulfate is recommended for prevention of eclampsia and treatment of seizures in pre-eclamptic women. 4

• Do not give concomitantly with calcium channel blockers due to risk of severe hypotension from potential synergism 4

Timing of Delivery in Hypertensive Disorders

Induction of labor should be advised for women with gestational hypertension or mild pre-eclampsia at 37 weeks' gestation. 4

• Induction is associated with improved maternal outcomes in this population 4
• All pre-eclamptic women should be hospitalized and closely monitored in obstetric centers with adequate maternal and neonatal intensive care resources 4

High-Risk Patient Considerations

Women with significant cardiac disease, complex medical conditions, or anticipated complications should deliver in tertiary centers with multidisciplinary specialist teams. 2, 1

Anticoagulation Management

Patients on therapeutic anticoagulation require switching to unfractionated heparin at least 36 hours before planned induction, with heparin discontinued 4-6 hours before delivery. 1

Critical Pitfalls to Avoid

• Do not initiate oxytocin when Bishop score is <5 without first performing cervical ripening—oxytocin alone is ineffective in this setting 1
• Do not declare failed induction before the mandatory 12-hour observation period after ripening, membrane rupture, and oxytocin 1
• Do not use misoprostol in women with prior cesarean section due to high uterine rupture risk 1
• Do not use dinoprostone in patients with active cardiovascular disease due to profound hemodynamic effects 2, 1
• Do not perform elective induction before 39 weeks 0 days as it is associated with adverse neonatal respiratory outcomes 5

Expected Outcomes

Based on the ARRIVE trial in low-risk nulliparous women at 39 weeks:

• Cesarean delivery rate: 18.6% with induction vs 22.2% with expectant management (RR 0.84) 1, 5
• Hypertensive disorders: 9.1% with induction vs 14.1% with expectant management (RR 0.64) 1, 5
• 63% of women had unfavorable cervix (Bishop <5) at randomization 1
• 99% of successfully induced women delivered within 24 hours 6