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

Abstract

Objective: The objective of this study was to estimate epidural timing's impact on fetal station during active labor.

Study design: This secondary analysis of a single-institution prospective cohort study included all term singleton pregnancies, stratified by parity. Those with early epidurals (placed at <6 cm) were compared with those with late epidurals (placed at ≥6 cm). The primary outcome was median fetal station from 6 to 10 cm. Secondary outcomes included rate of prolonged first or second stage of labor (>95%). Multivariable logistic regression adjusted for labor type.

Results: Among 7,647 women, 3,434 were nulliparous (2,983 with early epidurals and 451 with late epidurals) and 4,213 multiparous (3,141 with early epidurals and 1,072 with late epidurals). Interquartile ranges (IQRs) suggested fetal station at 6 cm was likely 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, but among nulliparous were associated with decreased risk of prolonged second stage (adjusted odds ratio: 0.66 [95% confidence interval: 0.44-0.99]).

Conclusion: Early epidurals were associated with lower fetal station in active labor but not prolonged first stage.