BACKGROUND AND PURPOSE:

• Curves derived from the Consortium on Safe Labor data differ from the previous Friedman curve
  • Active labor began at 6 cm dilation in multiparous and nulliparous patients and not 4 cm as per the Friedman curve
• 2014, ACOG/SMFM/Obstetric Care Consensus statement proposed that
  • Cesarean section rate could be lowered by not calling arrest of dilation at < 6 cm
  • In the 2^nd stage, multiparas could push for at least 2 hours and nulliparas for at least 3 hours
• Rosenbloom et al. (AJOG, 2017) sought to determine whether
  • Rates of arrest of dilation disorders have decreased thereby reducing the rate of cesarean delivery (CD) in low-risk women at term
  • Pushing duration prior to diagnosis of arrest of descent has increased, likewise reducing the rate of CD

METHODS:

• Secondary analysis of prospective cohort study
• All low risk patients presenting at ≥ 37 weeks’ gestation (2010 – 2014) for either spontaneous or induced labor
• Low risk was defined as patients like those in the Consortium on Safe Labor cohort
• Exclusion criteria
  • Previous CD, multiple gestation, nonvertex presentation, fetal anomalies, IUFD
  • Women presenting for scheduled CD
• Primary Outcomes
  • Rates of CD
  • Indications for CD
  • Average dilation at CD for arrest

RESULTS:

• 7845 eligible patients.
• There was no difference between 2010 and 2014 in CD rate (15.8% vs 17.7%)
• There was no difference between 2010 and 2014 in the median cervical dilation (5.5 cm vs 6.0 cm) at the time of CD for arrest of dilation
  • There was an increase in the time spent at last dilation from 3.8h in 2010 to 5.2h in 2014 (p-trend 0.02)
• There was no difference between 2010 and 2014 in the frequency of patients diagnosed with arrest of dilation at <6 cm (p-trend 0.56)
  • The median time spent at the last cervical dilation was 4.0h in 2010 and 6.7h in 2014 (p-trend 0.046)
• There were 206 CDs for arrest of descent
  • The median pushing time increased in multiparous patients from 1.1h in 2010 to 3.4h in 2014 (p-trend 0.009)
  • The median pushing time increased in nulliparous patients from 2.7h in 2010 to 3.8h in 2014 (p-trend 0.09)
• There were increasing adverse neonatal and maternal outcomes (p<0.001 for each)
  • The adjusted odds ratio (OR) for adverse maternal outcome for 2014 compared to 2010 was 1.66 (95%CI 1.27-2.17)
  • The aOR for adverse neonatal outcome in 2014 compared to 2010 was 1.80 (95%CI 1.36-2.36)
• Majority of arrest of dilation occurred in women undergoing induction of labor

CONCLUSION:

• Strengths of the study included prospective data collection
• Observational design so results reflect association and not causation
• Findings differ from previous study but authors point out the current study had a larger sample number over a longer period and patients had substantially higher BMI
• Moving to the new ‘6cm curve’ did not reduce the primary CD rate and there has been an increase in maternal and neonatal morbidity
• A randomized controlled trial is needed

Learn More – Primary Sources:

New Labor Management Guidelines and Changes in Cesarean Delivery Patterns

Related ObG Topics:

Can Evidence Based Interventions Reduce C-section Complications?

Induction to Prevent Stillbirths for Age 35 and Older: Impact on Cesarean Rates?

Labor induction and an unripe cervix: does it result in more C-sections?