What are the methods to induce labour?

Labor Induction Methods

For labor induction, use a combination of mechanical cervical ripening (60-80 mL Foley catheter for 12 hours) followed by low-dose oxytocin infusion (starting at 1-2 mU/min, increased by 1-2 mU/min every 40-60 minutes), which provides the safest and most effective approach for most patients. 1, 2, 3

Primary Induction Methods

Mechanical Cervical Ripening

• A single-balloon Foley catheter (60-80 mL) placed for 12 hours is the preferred initial method for cervical ripening, particularly in patients with unfavorable cervices (low Bishop scores). 3, 4
• Mechanical methods carry no reported risk of uterine rupture and are especially valuable in patients with prior cesarean delivery, where pharmacologic agents pose higher rupture risks. 5
• The Foley catheter can be used for outpatient cervical ripening in carefully selected low-risk women. 3

Pharmacologic Induction

Oxytocin (First-Line Pharmacologic Agent)

• Start with 1-2 mU/min intravenously and increase by 1-2 mU/min every 40-60 minutes until adequate contraction pattern is established (similar to normal labor). 1, 2
• The low-dose protocol significantly reduces uterine hyperstimulation episodes compared to traditional 20-minute interval protocols. 1, 6
• Oxytocin is indicated when the Bishop score is favorable or after mechanical ripening. 5, 2
• Continuous fetal heart rate and uterine activity monitoring is mandatory throughout oxytocin administration. 7, 2
• Discontinue oxytocin immediately if Category III fetal heart rate patterns or uterine hyperstimulation occur. 1, 2

Prostaglandins (Alternative Pharmacologic Agents)

• Misoprostol: 25 μg orally every 2-4 hours (or 50 μg every 4-6 hours if no more than 3 contractions per 10 minutes and no prior uterine surgery) can be combined with Foley catheter placement. 3
• Prostaglandin E2 (dinoprostone) is an option but carries theoretical risks of coronary vasospasm and more profound blood pressure effects than prostaglandin E1. 5
• Prostaglandins are contraindicated in patients with active cardiovascular disease due to hemodynamic effects. 5

Special Population Considerations

Prior Cesarean Delivery (VBAC Candidates)

• Oxytocin carries a 1.1% uterine rupture risk in women with prior cesarean, which is acceptable for induction when indicated. 5, 8
• Prostaglandin E2 increases rupture risk to 2%, while misoprostol carries a 13% rupture risk and is absolutely contraindicated in third trimester with prior cesarean. 5, 8
• Mechanical methods (Foley catheter) are strongly preferred for cervical ripening in this population due to absence of rupture risk. 5
• Enhanced monitoring is required throughout labor, and patients should be counseled that induction decreases VBAC success rates compared to spontaneous labor. 5, 8

Cardiovascular Disease

• Spontaneous labor onset is preferable to induction in women with heart disease whenever maternal and fetal status permit. 5
• When induction is necessary, mechanical methods (Foley catheter) are preferred over pharmacologic agents to avoid hemodynamic instability. 5
• Avoid dinoprostone in patients with active cardiovascular disease due to significant blood pressure effects. 5
• Timing should account for cardiac functional status, though standard guidelines do not exist for specific cardiac lesions. 5

Hypertensive Disorders

• Induction of labor at 37 weeks' gestation is recommended for women with gestational hypertension or mild pre-eclampsia, as it improves maternal outcomes. 5
• Optimal delivery timing depends on fetal wellbeing, gestational age, and severity of hypertensive disorder. 5

Adjunctive Techniques

Membrane Stripping

• Adding membrane stripping at the beginning of induction should be considered, as strong evidence shows it increases likelihood of spontaneous labor within 48 hours. 3, 4

Amniotomy

• Artificial rupture of membranes is indicated when the Bishop score is favorable, typically combined with oxytocin. 5
• The independent effect of amniotomy on labor progression remains uncertain. 4

Oxytocin Discontinuation During Active Labor

• Once 5-6 cm cervical dilation is achieved during induction, consider discontinuing oxytocin if adequate contractions are present, as endogenous oxytocin release may sustain labor. 3

Critical Safety Considerations

Contraindications to Oxytocin

• Never use oxytocin when cephalopelvic disproportion (CPD) is suspected or confirmed, as 40-50% of arrested active phase cases involve CPD. 1
• Perform thorough cephalopelvimetry before oxytocin use in arrested labor. 1

Response Assessment and Timing

• Most arrest disorders respond within 2-4 hours of oxytocin, though recent evidence suggests 2 hours is safer. 1
• If no cervical dilation occurs after oxytocin administration, proceed to cesarean delivery rather than continuing augmentation. 1
• Cesarean delivery should not be performed before 15 hours of oxytocin infusion with amniotomy, and ideally not before 18-24 hours. 3

Monitoring for Complications

• Watch for increasingly marked molding or deflexion, which indicates emerging CPD—proceed to cesarean earlier rather than continuing augmentation. 1
• Address inhibitory factors (excessive neuraxial blockade, narcotic analgesia, fetal malposition) before initiating oxytocin. 1

Term PROM Management

• For term prelabor rupture of membranes, initiate oxytocin infusion immediately (as soon as feasible) or within 12 hours if labor is not evident, as this approach balances infection risk against intervention. 3

Common Pitfalls to Avoid

• Do not use intrauterine pressure transducer measurements to guide oxytocin dosing—simple palpation successfully evaluates uterine activity unless obesity prevents it. 1
• Avoid prolonged induction attempts with unfavorable cervix—use mechanical ripening first. 5
• Never use misoprostol for cervical preparation or induction in women with prior cesarean delivery in the third trimester. 5
• Do not combine short-acting oral nifedipine with magnesium sulfate during induction, as this causes uncontrolled hypotension and fetal compromise. 5