The purpose of this study was to compare the effect of early epidural with the use of early intravenous analgesia on labor progression.

We systematically selected singleton, nulliparous term pregnancies with a spontaneous labor and analgesia placement ≤4 cm who were delivered at a hospital where the rate of epidural analgesia in labor increased from 1% (before) to 84% (after) in 1 year (a natural experiment). In the before period (n=223 pregnancies), 98% of women used intravenous analgesia, and 2% of women used epidural analgesia. In the after period (n=278 pregnancies), 92% of women used epidural analgesia, and 8% of women used intravenous analgesia. The median duration of labor by each centimeter of cervical dilation was computed and used as a measurement of labor progression.

After adjustment had been made for confounders, women in the after period had a slower labor progression only from 4 to 5 cm, compared with those women in the before period. Interestingly, the process of labor admission and epidural analgesia placement, rather than analgesia use per se, appeared to explain most of the slowdown. No significant difference in the rest of the active phase was observed between the 2 groups.

Our data support recent American College of Obstetricians and Gynecologists guidelines that the restraining use of epidural analgesia at <4 cm of cervical dilation is unnecessary.