What is the recommended induction of labor protocol for a patient eligible for the ARRIVE (A Randomized Trial of Induction Versus Expectant Management) trial at 39 weeks of gestation?

ARRIVE Trial Induction Protocol for Low-Risk Nulliparous Women at 39 Weeks

For patients eligible for the ARRIVE trial at 39 weeks gestation, induction of labor should be offered as it reduces cesarean delivery rates and hypertensive disorders of pregnancy compared to expectant management. 1

Patient Selection Criteria

Proper patient selection is critical for implementing the ARRIVE protocol:

• Low-risk nulliparous women
• Singleton pregnancy
• Vertex presentation
• No medical or obstetric complications
• Confirmed dating by early ultrasound:
  • For women with certain LMP: ultrasound confirmation before 21 weeks
  • For women with uncertain LMP: first-trimester ultrasound dating required
• Induction planned between 39 weeks 0 days and 39 weeks 4 days

Induction Protocol

Cervical Assessment

• Evaluate cervical status using modified Bishop score
• 63% of women in the ARRIVE trial had unfavorable cervix (Bishop score <5) 1

For Unfavorable Cervix (Bishop score <5):

1. Cervical Ripening:

   • Use a cervical ripening agent for unfavorable cervix 1
   • Recommended approach: 60-80mL single-balloon Foley catheter for 12 hours 2
   • Consider membrane stripping at the beginning of induction if feasible 2
   • Outpatient Foley ripening can be considered for low-risk women 2, 3

2. After Cervical Ripening:

   • Follow with either:
     • 25-μg oral misoprostol initially, then 25 μg every 2-4 hours, OR
     • 50 μg oral misoprostol every 4-6 hours (if no more than 3 contractions per 10 minutes and no previous uterine surgery), OR
     • Oxytocin infusion 2

For All Patients:

• Allow at least 12 hours after completion of cervical ripening, rupture of membranes, and use of uterine stimulant before considering cesarean for "failed" induction in latent phase 1
• Once 5-6 cm cervical dilation is achieved, consider discontinuing oxytocin if adequate contractions are present 2
• Cesarean delivery should not be performed before 15 hours of oxytocin infusion and amniotomy (if feasible) 2
• Ideally, allow 18-24 hours of oxytocin infusion before considering cesarean for failed induction 2

Key Benefits and Considerations

Benefits:

• Reduced cesarean delivery rate (18.6% vs 22.2% with expectant management) 1, 4
• Reduced hypertensive disorders of pregnancy (9.1% vs 14.1%) 1
• Number needed to treat to prevent one cesarean delivery: 28 women 1

Important Considerations:

• Accurate dating is crucial to avoid iatrogenic early term or preterm delivery 1
• Resource allocation must be considered - prioritize medically indicated inductions 1
• Implementation depends on facility capacity and available staff (nurses, anesthesiologists) 1

Pitfalls to Avoid

• Performing induction before confirmed 39 weeks 0 days (increased risk of neonatal respiratory morbidity) 1
• Declaring "failed induction" too early (allow adequate time as per protocol) 1
• Applying ARRIVE protocol to multiparous women (evidence only supports nulliparous women) 1
• Using in women without confirmed early dating ultrasound 1
• Implementing without considering institutional resources and capacity 1

The ARRIVE protocol represents a significant shift in obstetric practice, showing that elective induction at 39 weeks in properly selected low-risk nulliparous women can improve maternal outcomes without increasing adverse neonatal outcomes 1, 4.