What are the key findings and recommendations of the ARRIVE (A Randomized Trial of Induction Versus Expectant Management) trial regarding elective induction of labor at 39 weeks of gestation?

Key Findings and Recommendations of the ARRIVE Trial

Elective induction of labor at 39 weeks in low-risk nulliparous women is associated with lower rates of cesarean delivery and hypertensive disorders of pregnancy compared to expectant management, without increasing adverse neonatal outcomes. 1

Study Design and Population

The ARRIVE (A Randomized Trial of Induction Versus Expectant Management) trial was a large multicenter, unmasked, randomized controlled trial conducted by the Eunice Kennedy Shriver National Institute of Child Health and Human Development Maternal-Fetal Medicine Units Network from 2014 to 2017. The study included:

• 6,106 low-risk nulliparous women (first-time mothers)
• 41 academic and community-based hospitals
• Randomization between 38 weeks 0 days and 38 weeks 6 days of gestation
• Induction group: planned induction at 39 weeks 0 days through 39 weeks 4 days
• Expectant management group: awaited spontaneous labor or medically indicated induction

Key eligibility criteria included:

• Nulliparous women (first pregnancy)
• Reliable dating confirmed by early ultrasound
• No obstetric or medical complications
• Singleton pregnancy in vertex presentation

Primary Results

Maternal Outcomes

• Cesarean delivery rate: 18.6% in induction group vs 22.2% in expectant management group (RR 0.84; 95% CI, 0.76-0.93; P<0.001) 1, 2
• Hypertensive disorders of pregnancy: 9.1% in induction group vs 14.1% in expectant management group (RR 0.64; 95% CI, 0.56-0.74; P<0.001) 1
• Number needed to treat (NNT) to prevent one cesarean delivery: 28 women 1

Neonatal Outcomes

• Primary composite outcome (perinatal death or severe neonatal morbidity): 4.3% in induction group vs 5.4% in expectant management group (RR 0.80; 95% CI, 0.64-1.00; P=0.049) 1, 2
  • This difference did not reach the pre-specified statistical significance threshold of 0.046

Supporting Evidence from Meta-analyses

A meta-analysis of 6 cohort studies including over 650,000 women confirmed the ARRIVE findings, showing that elective induction at 39 weeks was associated with:

• Lower cesarean delivery rates (26.4% vs 29.1%; RR 0.83; 95% CI, 0.74-0.93)
• Lower peripartum infection rates (2.8% vs 5.2%; RR 0.53; 95% CI, 0.39-0.72)
• Reduced neonatal respiratory morbidity (0.7% vs 1.5%; RR 0.71; 95% CI, 0.59-0.85)
• Lower perinatal mortality (0.04% vs 0.2%; RR 0.27; 95% CI, 0.09-0.76) 3

Key Recommendations from SMFM

Based on the ARRIVE trial, the Society for Maternal-Fetal Medicine (SMFM) made the following recommendations:

1. It is reasonable to offer elective induction of labor to low-risk nulliparous women at 39 weeks 0 days of gestation, ensuring women meet the ARRIVE trial eligibility criteria 1

2. Elective induction should not be offered under circumstances inconsistent with the ARRIVE protocol unless as part of research or quality improvement 1

3. Further research should be conducted to measure the impact of this practice outside clinical trial settings 1

Important Considerations for Implementation

Patient Selection

• Accurate pregnancy dating is crucial - all ARRIVE participants had dating confirmed by early ultrasound 1
• For women with certain last menstrual period, ultrasound confirmation occurred at <21 weeks
• For uncertain last menstrual period, only women with first-trimester ultrasound dating were included

Labor Management

• 63% of participants had an unfavorable cervix (modified Bishop score <5) at randomization 1
• Cervical ripening was recommended for unfavorable cervix, though specific methods were not mandated
• Providers were asked to allow at least 12 hours after cervical ripening before considering cesarean for "failed induction" 1

Oxytocin Regimen Considerations

• Recent analysis suggests low-dose oxytocin regimens (starting and incremental increase ≤2 mU/min) may be preferable to mid/high-dose regimens for induction 4
• Mid/high-dose regimens were associated with more transient neonatal respiratory support without reducing cesarean rates 4

Limitations and Caveats

1. Generalizability concerns: Only 27% of eligible women enrolled in the trial 1

2. Resource implications: Implementation requires adequate staffing and facility capacity 1

3. Applicability to multiparous women: The ARRIVE trial only included nulliparous women, though subsequent research suggests similar benefits in parous women 5

4. Shared decision-making is essential: Some women may prefer expectant management with the possibility of spontaneous labor 1

5. Avoid induction before 39 weeks: Early term neonates (37-38 weeks) have increased risk of respiratory morbidity 1