BACKGROUND AND PURPOSE:

• Early amniotomy during induction likely decreases the duration of labor
  • Effect on cesarean delivery is less well understood
• Battarbee et al. (American Journal of Perinatology, 2020) assessed the association between amniotomy in nulliparous women and risk for cesarean delivery

METHODS:

• Secondary analysis of the ARRIVE RCT (NICHD/MFMU)
  • Purpose of original study was to assess perinatal outcomes in nulliparous women randomized to elective induction at 39 weeks vs expectant management
• Participants (inclusion criteria)
  • Low-risk, nulliparous women
  • Induction ≥38 weeks using oxytocin
  • Excluded were women with antepartum stillbirth or fetal anomaly
• Study design
  • The authors compared outcomes between
    • Women with amniotomy
    • Women with intact membranes and no amniotomy
  • Comparisons were performed at six 2-hour time intervals
    • Before oxytocin initiation
    • 0 to <2 hours after oxytocin
    • 2 to <4 hours after
    • 4 to <6 hours after
    • 6 to <8 hours after
    • 8 to <10 hours after
• Statistical analysis
  • Multivariable logistic regression
  • Adjustments
    • Maternal age | BMI | Race/ethnicity | Modified Bishop score on admission | Treatment group | Hospital
• Primary outcome
  • Cesarean delivery
• Secondary outcomes
  • Maternal and neonatal complications

RESULTS:

• 2,854 (46.7% of women from the parent trial) met inclusion criteria
  • Amniotomy: 82.0%
    • The majority were performed between 2 and <6 hours after oxytocin
• After adjusting for confounders, only 6 to <8 hours after oxytocin was associated with lower cesarean rates
  • Amniotomy 6 to <8 hours after oxytocin: 21.9% cesarean rate
  • Without amniotomy: 29.7% cesarean rate
  • Adjusted odds ratio (OR) 0.61 (95% CI, 0.42 to 0.89)
• Amniotomy at time intervals ≥4 hours after oxytocin was associated with lower odds of labor lasting more than 24 hours
  • 4 to <6 hours after oxytocin: aOR 0.59 (99% CI, 0.41–0.86)
  • 6 to <8 hours after oxytocin: aOR 0.38 (99% CI, 0.24–0.61)
  • 8 to <10 hours after oxytocin: aOR 0.37 (99% CI, 0.21–0.64)
• Amniotomy at time intervals ≥2 hours and <8 hours after oxytocin was associated with lower odds of maternal hospitalization >3 days
• There was no association between amniotomy and postpartum or neonatal complications including
  • Chorioamnionitis | PPH | Infection | NICU admission

CONCLUSION:

• For nulliparous women at term, amniotomy during induction was associated with a risk of cesarean similar or lower compared to that of women with no amniotomy and may be associated with a shorter labor duration

Learn More – Primary Sources:

Maternal and Neonatal Outcomes Associated With Amniotomy Among Nulliparous Women Undergoing Labor Induction at Term

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