What are the methods for inducing labour?

Methods for Labor Induction

Labor induction can be performed using various pharmacological and mechanical methods, with the choice depending primarily on cervical readiness assessment and individual patient factors. 1, 2

Assessment Before Induction

• The Bishop score should be used to evaluate cervical readiness by assessing dilation, effacement, consistency, position, and station of the presenting part 1
• A higher Bishop score (above 8) indicates a favorable cervix and predicts a greater likelihood of successful vaginal delivery 1
• Accurate dating confirmation with early ultrasonography is essential before induction to avoid iatrogenic early term or preterm delivery 3

Pharmacological Methods

Oxytocin

• Oxytocin is administered via intravenous infusion with accurate control of the rate using an infusion pump 4
• Standard preparation: 10 units of oxytocin combined with 1,000 mL of physiologic solution (10 mU/mL) 4
• Initial dosing should be 1-2 mU/min with gradual increases of 1-2 mU/min until a normal labor contraction pattern is established 4
• Continuous monitoring of fetal heart rate and uterine contractions is essential during oxytocin administration 4
• Oxytocin should be discontinued immediately if uterine hyperactivity or fetal distress occurs 4
• Oxytocin is most effective when the cervix is already favorable or after cervical ripening has been achieved 5

Prostaglandins

• Prostaglandins are recommended for cervical ripening when the Bishop score is unfavorable 2
• Prostaglandin E2 (dinoprostone) and prostaglandin E1 (misoprostol) are the most commonly used agents 5
• Misoprostol can be administered orally (25 μg initially, followed by 25 μg every 2-4 hours) or 50 μg every 4-6 hours if no more than 3 contractions per 10 minutes 2
• Misoprostol should NOT be used for cervical preparation or induction in women with previous cesarean delivery due to increased risk of uterine rupture (13% in one study) 3

Mechanical Methods

Balloon Catheter (Foley Catheter)

• A 60-80 mL single-balloon Foley catheter can be used for cervical ripening for approximately 12 hours 2
• Mechanical methods reduce the risk of uterine hyperstimulation compared to prostaglandins but may increase maternal and neonatal infectious morbidity 6
• No uterine ruptures have been reported when using a Foley catheter for cervical ripening in women with previous cesarean delivery 3
• Outpatient Foley catheter ripening can be considered for low-risk women 2, 7

Other Mechanical Methods

• Membrane sweeping/stripping can reduce post-term gestations and can be added at the beginning of induction 2, 6
• Amniotomy (artificial rupture of membranes) can be performed once the cervix is favorable 5
• Laminaria (hygroscopic dilators) can be used for cervical ripening 6

Combination Methods

• A combination of mechanical methods (Foley catheter) with pharmacological methods (misoprostol or oxytocin) is often more effective than single methods 2
• The most effective approach for labor induction is a combination of 60-80 mL single-balloon Foley catheter for 12 hours followed by either oral misoprostol or oxytocin infusion. 2

Special Considerations

Elective Induction at 39 Weeks

• Elective induction of labor at 39 weeks 0 days of gestation is reasonable to offer to low-risk nulliparous women 3
• Benefits include decreased cesarean delivery rates (18.6% vs 22.2%) and decreased risk of hypertensive disorders of pregnancy (9.1% vs 14.1%) 3
• To prevent one cesarean delivery, 28 low-risk nulliparous women would need to undergo elective induction at 39 weeks 3

Induction After Prelabor Rupture of Membranes

• Induction with oxytocin immediately or up to 12 hours after term prelabor rupture of membranes is recommended if labor is not evident 2

Previous Cesarean Delivery

• Oxytocin induction carries a 1.1% risk of uterine rupture in women with previous cesarean delivery 3
• Prostaglandin E2 has a 2% risk of uterine rupture in women with previous cesarean delivery 3
• Misoprostol is contraindicated in women with previous cesarean delivery due to high risk (13%) of uterine rupture 3
• Mechanical methods like Foley catheter appear safer for cervical ripening in women with previous cesarean delivery 3

Duration of Induction

• Cesarean delivery should not be performed before 15 hours of oxytocin infusion and amniotomy 2
• Ideally, allow 18-24 hours of oxytocin infusion before considering cesarean delivery for failed induction 2
• Once 5-6 cm of cervical dilation is achieved during induction, consideration can be given to discontinue oxytocin if adequate contractions are present 2

Common Pitfalls and Caveats

• Accurate dating confirmation is crucial before induction to avoid iatrogenic early term delivery 3
• Continuous monitoring of fetal heart rate and uterine contractions is essential during induction 4
• Oxytocin should be discontinued immediately if uterine hyperactivity or fetal distress occurs 4
• Misoprostol should never be used in women with previous cesarean delivery 3
• Shared decision-making when counseling women about elective induction is critical 3