BACKGROUND AND PURPOSE: 

• Previous studies examined the effect of early epidural initiation using the Friedman labor curve, which defines active labor at ≥4 cm cervical dilation 
• The current ‘modern’ ACOG labor curve uses the terminology ‘active phase of labor’ at ≥6 cm 
• Lewkowitz et al. (American Journal of  Perinatology, 2018) sought to assess the impact of epidural timing on fetal station during active labor 

METHODS: 

• Secondary analysis of a single-institution prospective cohort study  
• Participants: Term (≥37 weeks) singleton pregnancies, stratified by parity 
• Patients received either 
  • Early epidural (placed at <6 cm)  
  • Late epidural (placed at ≥ 6 cm) 
• Epidural placed on patient request  
• Continuous infusion of sufentanil 50 µg in bupivacaine 100 mg through the epidural catheter 
  • Rate was up- or down-titrated by the anesthesia provider 
  • Patient could initiate small bolus as needed  
• Fetal station was recorded on a −3 to +3 scale rather than a −5 to +5 scale 
  • Cervical examinations performed at the time of epidural placement only if clinically indicated  
• Primary outcome: Median fetal station from 6 to 10 cm 
• Secondary outcomes: Prolonged first or second stage of labor defined as
  • Duration of stage greater than the 95th percentile of the study cohort
• Multivariable logistic regression was adjusted for labor type 

RESULTS: 

• 7,647 women were included 
  • 3,434 women were nulliparous: 2,983 had early epidurals and 451 had late epidurals 
  • 4,213 women were multiparous: 3,141 had early epidurals and 1,072 had late epidurals 
• Fetal station at 6 cm appeared lower among those with early epidurals  
  • Nulliparous: median head station −1 (IQR: −1 to 0) for early epidural vs. −1 (IQR: −2 to 0) for late epidural (p < 0.01)  
  • Multiparous: −1 (IQR: −2 to 0) for early epidural vs. −1 (IQR: −3 to −1) for late epidural (p < 0.01) 
• Early epidurals were not associated with increased risk of prolonged first stage 
• Among nulliparous women, there was an association between early epidural and decreased risk of prolonged second stage  
  • Adjusted odds ratio 0.66 (95% CI, 0.44–0.99) 

CONCLUSION: 

• Early epidurals (<6 cm) were associated with  
  • Lower fetal station during active labor for all women and at the start of the second stage of labor for multiparous women without evidence of prolonged first stage 
  • Decreased risk of prolonged second stage of labor  
• The authors state that this data supports the safety of providing epidural pain relieve prior to 6 cm cervical dilation 

Learn More – Primary Sources: 

Epidurals and the Modern Labor Curve: How Epidural Timing Impacts Fetal Station during Active Labor

Related ObG Topics:

Can Maternal Pulse Pressure be Used to Determine the Need for Fluid Bolus Prior to Epidural?

Does Epidural Anesthesia Impact the Second Stage of Labor?

Can Fetal Head Size Help Predict Risk of Cesarean Section?