Epidural Prolongs Second Stage of Labor by More Than 2 Hours

Laurie Barclay, MD

February 05, 2014

Duration of second-stage labor was more than 2 hours longer when epidural anesthesia was given during labor for both nulliparous and multiparous women, according to a retrospective cohort study reported in the March issue of Obstetrics & Gynecology. The duration of second-stage labor observed in the study is twice as long as typically estimated for epidurals in clinical guidelines.

"Minimizing primary cesarean delivery is a priority," write Yvonne W. Cheng, MD, PhD, from the Division of Maternal-Fetal Medicine, Department of Obstetrics, Gynecology and Reproductive Sciences, University of California, San Francisco, and colleagues. "Two common indications of cesarean during labor are active phase arrest and arrest of descent."

The study goal was to compare the duration of second stage of labor with and without epidural anesthetic given during labor, using an historical sample of 42,268 women who delivered vaginally with normal neonatal outcomes. The investigators compared median durations and 95th percentiles of second stage of labor for women given or not given epidurals, with stratification by parity. The Kruskal-Wallis test and Kaplan-Meier survival analysis allowed statistical comparisons.

Epidural Associated With Longer Second Stage

For nulliparous women, the 95th percentile duration of second-stage labor was 197 minutes without epidural and 336 minutes with epidural, a significant difference of 2 hours and 19 minutes (P < .001). The difference for multiparous women was 2 hours and 54 minutes (81 minutes without epidural and 255 minutes with epidural; P < .001).

The duration of labor became progressively longer in more recent years for unclear reasons. However, the study authors suggested that this might be attributed to changing obstetric characteristics, such as higher proportion of induced or augmented labor, less frequent forceps and high station operative deliveries, and increased prevalence of obesity and gestational weight gain.

"Although recommendations for intervention during the second stage of labor have been made based on a 1-hour difference in the setting of epidural use, it appears that the 95th percentile duration is actually more than 2 hours longer with epidural during labor for both nulliparous and multiparous women," the study authors write.

Prolonged Labor May Need to Be Redefined

They note that according to use of current definitions of prolonged labor, nearly one third of nulliparous women receiving an epidural would be labeled as having abnormal labor, which would likely result in potentially unnecessary interventions.

"Although the majority of obstetrician–gynecologists subscribe to the clinical guidelines of giving 1 additional hour to account for epidural use, it appears that the differences from epidural at the 95th percentiles may be approximately double," the study authors write. "Thus, the current definition of prolonged second stage of labor may be too stringent."

Limitations of this study include missing data or inaccurate information, potentially creating bias; long study period; and analysis of data from a single academic institution, which could potentially limit generalizability.

"Although labor norms should not be established based on this study alone, our findings, along with those of others, suggest that current definitions of prolonged second stage of labor in the setting of an otherwise reassuring fetal status may be insufficient," the study authors conclude. "There exists a need to establish proper second stage of labor norms to reflect modern obstetrics."

The study authors have disclosed no relevant financial relationships.

Obstet Gynecol 2014;123:527-535.

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